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The toxicity of PCB-156 (2,3,3′,4,4′,5-hexachlorobiphenyl) was investigated in rats following subchronic dietary exposure. Groups of 10 male and female Sprague-Dawley rats were administered PCB-156 in the diet at 0, 0.01, 0.1, 1 or 10 ppm for 90 days. Dose-dependent increases were detected for the liver, lung and kidney weights, as well as for the liver EROD, PROD and UDPGT enzyme activities and liver uroporphyrin concentration. Dose-dependent decreases were observed in final body weight, body weight gain, and thymus weight. Apolar retinoid concentrations were decreased in the liver and lungs and increased in the kidneys. Histopathological examination of the liver, thyroid, and thymus showed mild to moderate dose-related changes. A LOAEL of 0.01 ppm was established, based on reduced apolar liver retinoid concentration. Benchmark dose-modelling corroborated the sensitivity of liver retinoid endpoints. The lower confidence limits (BMDL) for a 5% decrease in apolar liver retinoid concentrations were 0.0009 and 0.0007 ppm, respectively, in males and females, corresponding to a daily dose of 0.06 µg PCB-156 per kg body weight. Organizing dose-response data for the individual hepatic endpoints along the PCB-156 dosing scale revealed a sequence of events compatible with a causal link between depletion of apolar retinoids and the other liver biochemistry and pathology findings. Taken together, data suggest that the retinoid endpoints should be further evaluated for a causal relationship to PCB-induced liver toxicity and that retinoid system endpoints are identified and characterized to support health risk assessment in the emerging research fields of endocrine disruption and mixture toxicology.

This investigation reports the effects of various terminal procedures, and how they modified the responses to a toxicant (polychlorinated biphenyls [A1254], 130 mg/kg/day × 5 days) administered by gavage to Sprague-Dawley male rats. Terminal procedures included exsanguination via the abdominal aorta under anesthesia (isoflurane inhalation or Equithesin injection), decapitation with or without anesthesia, or narcosis induced by carbon dioxide inhalation. Effects of repeated anesthesia were also tested. Terminal procedures induced confounding stress responses, particularly when Equithesin was used. The terminal procedures modified the conclusions about effects of A1254 on the concentrations of corticosterone, insulin, glucagon, glucose, alkaline phosphatase, lactate dehydrogenase, uric acid, and blood urea nitrogen, from nonstatistically significant to significant changes, and in the case of luteinizing hormone from a statistically significant increase to a significant decrease. Investigations of effects of toxicants should be designed and interpreted considering potential changes induced by the selection of a terminal procedure.

Dermal absorption of contaminants from soils at federal contaminated sites in Canada was investigated using one hydrophile, (14)C-ethylene glycol (EG), and one lipophile, (14)C-nonylphenol (NP). In vitro dermal absorption of EG and NP was examined in dermatomed (0.4-0.5 mm) human skin using Bronaugh Teflon flow-through cells with Hanks HEPES buffered (pH 7.4) receiver solution with 4% bovine serum albumin (BSA). Tests were conducted under occlusive conditions with and without a commercial gardening soil spiked with EG or NP applied to skin at a soil load of 5 mg/cm(2). With percent absorption in skin depot included, a total of 9.9 + or - 6.28% (n = 6) and 34.8 + or - 8.47% (n = 6) absorption of EG with and without soil, respectively, and 20.6 + or - 5.56% (n = 7) and 41.1 + or - 6.46% (n = 7) of NP, with and without soil, respectively, were obtained. For tests without soil a reverse pattern was observed with significantly lower percent absorption into the receiver than depot with the lipophile NP, but significantly higher percent absorption in receiver versus depot for the hydrophile EG. This pattern was different in tests with soil, and caution needs to be exercised when extrapolating data from in vitro tests conducted without soil in human health risk assessments at contaminated sites.

Dermal absorption of human breast skin obtained fresh from a local hospital was tested before and after freezer storage at -19 degrees C for 30 or 60 d. Dermatomed skin (0.4-0.5 mm) was tested in vitro using the Bronaugh flow-through diffusion cells perfused at 1.5 ml/h with receiver solution (Hanks HEPES buffered basal saline containing 4% bovine serum albumin [BSA]). Six 14C-radiolabeled chemicals ranging in lipophilicity were tested, including benzo[a]pyrene (BaP), ethylene glycol (EG), methyl parathion (MP), naphthalene (Nap), nonyl phenol (NP), and toluene (Tol). There was significantly lower percent dermal absorption into the receiver solution for two of the six chemicals (BaP and Tol) with the skin depot excluded. However, with percent dermal absorption defined as that including the skin depot, with the exception of the BaP data for skin frozen 30 d, there was no significant difference between percent dermal absorption data for fresh unfrozen controls and those stored frozen for all 6 test chemicals for both 30 and 60 d freezer storage times. These results suggested with skin depot included that freezer storage may have potential for preserving human skin for in vitro absorption tests of environmental contaminants; however, optimal freezer storage conditions such as temperature and storage duration and their effects on skin viability and dermal metabolism need to be determined.

Human populations are simultaneously exposed to a variety of anthropogenic contaminants. However, despite extensive literature on animal exposure to single compounds, data on the toxicity of complex mixtures are scarce. The Northern Contaminant Mixture (NCM) was formulated to contain the 27 most abundant contaminants in the same relative proportions found in the blood of Canadian Arctic populations. Sprague-Dawley rat dams were dosed from the first day of gestation until weaning with methylmercury (MeHg), polychlorinated biphenyls (PCBs) or organochlorines pesticides (OCs) administered either separately or together in the NCM. An additional control group for hypothyroxinemia was included by dosing dams with the goitrogen 6-propyl-2-thiouracil (PTU). Offspring growth, survival, serum thyroxine and Thyroid Stimulating Hormone (TSH) levels, thyroid gland morphology, brain taurine content and cerebellum and hippocampus protein expression patterns resulting from such exposures were monitored. Pups' increased mortality rate and impaired growth observed in the NCM treatment group were attributed to MeHg, while decreased circulating thyroxine levels and perturbations of thyroid gland morphology were mostly attributable to PCBs. Interestingly, despite comparable reduction in serum thyroxine levels, PCBs and PTU exposures produced markedly different effects on pup's growth, serum TSH level and brain taurine content. Analysis of cerebellum and hippocampus protein expression patterns corroborated previous cerebellum gene expression data, as contaminant co-exposure in the NCM significantly masked the effects of individual components on protein two-dimensional electrophoresis patterns. Identification by MALDI-TOF/TOF MS of differentially expressed proteins involved notably in neuronal and mitochondrial functions provided clues on the cellular and molecular processes affected by these contaminant mixtures.

As part of the program to investigate mixture effects of environmental pollutants, this study describes clinical, biochemical, and histopathological effects in rats perinatally exposed to a mixture of persistent organochlorine pollutants and methylmercury that simulates the blood contaminant profile of humans residing in the Canadian Arctic. Groups of pregnant rats were administered orally 0, 0.05, 0.5, or 5 mg/kg body weight (bw)/d of a reconstituted mixture of organochlorine pollutants (referred to as mixture hereafter) from gestational day (GD) 1 to postnatal day (PND) 23. Positive and vehicle controls were given Aroclor 1254 (Aroclor hereafter, 15 mg/kg bw) and corn oil (vehicle), respectively. After parturition, the pups were colled to 8 per litter on PND 4, and killed on PND 35, 77, or 350, when tissues were collected for analysis. Gestational and lactational exposure of rats to mixture up to 5 mg/kg bw produced adverse effects in the offspring, including growth suppression, decreased spleen and thymic weights, increased serum cholesterol and liver microsomal enzyme activities, lower liver retinoid levels, and histological changes in the liver, thyroid, and spleen. Histological changes in the liver consisted of hepatic inflammation, vacuolation, and hypertrophy, while alterations in the thyroid were characterized by hypertrophy and hyperplasia of follicles. The hepatic and thyroidal effects were mild even at the highest dose. The spleen showed a dose-dependent atrophy in the lymphoid nodules and periarteriolar lymphatic sheath regions. Aroclor produced effects similar to those seen in the highest mixture group. In summary, this study demonstrates that exposure to the reconstituted mixture at 5 mg/kg bw produced growth suppression, changes in organ weights, and biochemical and histopathological changes in liver, thyroid, and spleen. This study also demonstrated that the blood level in rats given the 5-mg/kg dose, where most of the effects were observed, is 100-fold higher than the blood level in the 0.05-mg/kg group, which is comparable to that found in humans living in the Canadian Arctic region.

Dermal absorption of the lipophile and potential carcinogen benzo[a]pyrene (BaP) in soils from contaminated sites was simulated in vitro using human skin exposed to 14C-BaP-spiked soil. This study is the first in a series of tests at Health Canada with several soil contaminants spanning a wide range of lipophilicity conducted with viable human skin. Breast skin was obtained fresh from a local hospital and dermatomed to a thickness of 0.4-0.5 mm. Teflon Bronaugh diffusion cells were perfused with HEPES buffered Hanks saline (pH 7.4) with 4% bovine serum albumin (BSA) and fractions were collected at 6-h intervals for up to 24 h exposure either to 14C-BaP applied in acetone or spiked in a commercial gardening soil. As skin depot 14C levels were still high at 24 h, the study was repeated for up to 42 h to examine skin depot bioavailability. Skin was washed with soapy water at 24 h in both the 24- and 42-h studies. Exposure to 14C-BaP both with and without soil was conducted in triplicate with skin specimens from at least 4 patients. In the 24-h exposure tests including the skin depot there was 15 and 56% absorption with and without soil, respectively. The lower total percent absorption from the spiked soil applied to skin resulted from lower depot absorption of 8% with and 45% without soil. Data for 42-h studies were similar and revealed no significant decrease in skin depot levels. Including the 42-h depots there was 16 and 50% absorption with and without soil, respectively, with respective depots of 7 and 39%. As there was no significant difference between the 24- and 42-h depots both with and without soil, the data suggest the depot for BaP was not bioavailable for at least the additional 18-h post soap wash exposure. The bioavailability of BaP is discussed in relation to previous in vitro and in vivo studies in perspective with dermal exposure to contaminated soils.

In vitro tests with fresh dermatomed (0.3 to 0.4 mm thick) female breast skin and one leg skin specimen were conducted in Bronaugh flow-through Teflon diffusion cells with three chemicals used to simulate chemical warfare agents: 14C-radiolabeled methyl salicylate (MES), ethyl parathion (PT), and malathion (MT), at three dose levels (2, 20, and 200 mM). Tests were conducted at a skin temperature of 29 degrees C using a brief 30-min exposure to the chemical and a 6.5-h receivor collection period. Rapid absorption of all three chemicals was observed, with MES absorbed about 10-fold faster than PT and MT. For MES, PT, and MT, respectively, there was 32%, 7%, and 12% absorption into the receivor solution (Hank's HEPES buffered saline with 4% bovine serum albumin [BSA], pH 7.4) at the low dose (2 mM), 17%, 2%, and 3% at the medium dose (20 mM), and 11%, 1%, and 1% at the high dose (200 mM) levels. Including the skin depot for MES, PT, and MT, respectively, there was 40%, 41%, and 21% (low dose), 26%, 16%, and 8% (medium dose), and 13%, 19%, and 10% (high does) absorption. Efficacy of skin soap washing conducted at the 30 min exposure time ranged from 31% to 86%, varying by chemical and dose level. Skin depot levels were highest for the relatively lipophilic PT. "Pseudo" skin permeability coefficient (K(p)) data declined with dose level, suggesting skin saturation had occurred. An in-depth comparison with literature data was conducted and risk assessment of first responder exposure was briefly considered.

The objective of this work was to evaluate potential interactions between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and polychlorinated biphenyls congeners (PCBs) in rats. Groups of five adult female rats were given 0, 2.5, 25, 250, or 1000 ng TCDD/kg body weight/day or TCDD in combination with a mixture of PCB congeners at a concentration of 2 or 20 µg kg−1 body weight/day by gavage for 28 days. After the 28-day treatment period, the rats were killed for the analysis of biochemical, liver enzyme activities, and hematological and pathological end points. Growth suppression, increased absolute and relative liver weights, and decreased thymic weight were observed in the 1000 ng TCDD group alone, or the groups receiving a mixture of 1000 ng TCDD and 2 and 20 µg PCBs. TCDD-increased liver and thymic weights were not altered by PCBs; however, growth suppression was more pronounced in animals receiving 1000 ng TCDD and 2 µg PCBs. Increased hepatic microsomal methoxy resorufin-O-demethylase and ethoxy resorufin...

Liver alterations were stereologically determined in five groups, each of 10 male and female Sprague–Dawley weanling rats fed PCB 105 (2,3,3′,4,4′-pentachlorobiphenyl) for 13 weeks at concentrations of 0.05, 0.5, 5, and 50 ppm mixed with corn oil. Animals from two groups receiving the oil in diets served as controls for each gender. A significant increase in mean volume fraction (VF) of smooth endoplasmic reticulum (SER) profiles was estimated in hepatocytes of female rats in 0.5, 5, and 50 ppm groups. A significant decrease in VF of mitochondria in female rats at 50 ppm was detected. In addition, a decrease in VF of lipid droplets was measured in female rats at 0.5, 5, and 50 ppm groups. No difference was found in VF of rough endoplasmic reticulum (RER) cisternae, and peroxisome profiles at any concentration of the PCB in either male or female animals as compared to baseline values from controls. A significant elevation of baseline VF for RER in female rats was detected in comparison with males. In the p...

A 4-week oral study was conducted in male rats to characterize and compare the toxicity of four aliphatic ethers (butyl ether, BE; ethyl hexyl ether, EHxE; methyl heptyl ether, MHpE; and 1,6-dimethoxyhexane, DMH) which have been proposed as high-cetane diesel additives. Male Sprague-Dawley rats (280 ± 20 g) were divided into groups of seven animals each and were administered by gavage low (2 mg/kg body weight), medium (20 mg/kg) or high (200 mg/kg) doses of BE, EHxE, or MHpE, 5 days per week for 4 weeks. Another group of animals was administered DMH at 200 mg/kg while the control group received the vehicle (corn oil at 1 ml/100 g bw) only. At the end of the treatment period, relative testis weights and thymus weights were significantly decreased in the DMH group but not in animals receiving BE, EHxE, or MHpE. Microscopic examination revealed degeneration of the seminiferous tubules and reduction of sperm density in the epididymides in the DMH treatment group. Urinary creatine/creatinine ratio, a sensitive indicator of testicular damage, was markedly elevated in the DMH treated animals but not in those treated with BE, EHxE, or MHpE. In the bone marrow, DMH caused mild dyserythropoiesis and dysthrombopoiesis, while BE, EHxE, and MHpE produced mild increases in granulocytes and myelocyte/erythrocyte ratio. All four ethers at 200 mg/kg caused mild histological changes in the thyroid but no significant modulation in the circulating thyroxin (T4) or triiodothyronine (T3) levels. All four ethers produced hepatic effects at 200 mg/kg consisting of mild, adaptive histological changes, increased urinary ascorbic acid output, and elevation in the activities of one or more xenobiotic metabolizing enzymes (benzyloxyresorufin-O-dealkylase, UDP-glucuronosyltransferase, glutathione-S-transferases). The level of 2-methoxyacetic acid (MAA), a known testicular and developmental toxin, was significantly increased in the urine and plasma of animals treated with DMH but not in those administered the high dose BE, EHxE, or MHpE. Amomg the individual rats treated with DMH, the MAA level appeared to correlate with the severity of toxicity such as testicular and thymic weights, and urinary creatine/creatinine ratio. It is concluded that BE, EHxE, and MHpE differed from DMH in that they did not produce testicular or thymic toxicity. All four ethers at high dose caused changes to the thyroid, liver and bone marrows that were mild and adaptive in nature. MAA appeared to be the proximal toxicant in DMH treated animals but the route by which DMH is metabolized to MAA remains to be elucidated.

A large multi-disciplinary study was conducted to investigate the systemic, neurodevelopmental, neurochemical, endocrine, and molecular pathological effects of a mixture of reconstituted persistent organochlorine pollutants (POP) based on the blood profiles of Canadians residing in the Great Lakes/St. Lawrence region. This report outlines the overall study design and describes the systemic effects in rat offspring perinatally exposed to the POP mixture. Maternal rats were administered orally 0, 0.013, 0.13, 1.3, or 13 mg/kg bw/day of the mixture from gestational day (GD) 1 to postnatal day (PND) 23. Positive and negative controls were given Aroclor 1254 (15 mg/kg bw/ day) and corn oil (vehicle), respectively. The rat pups were reared, culled to 8 per litter, and killed on postnatal days 35, 70, and 350, at which time tissues were collected for analysis. Exposure to high doses of the mixture elicited clinical, biochemical, and pathological changes and high mortality rates in rat offspring. Aroclor 1254 produced similar effects but a lower mortality than was seen in POP mixture groups. Biochemical changes consisted of increased liver microsomal activities and elevated serum cholesterol. Hepatomegaly was observed in the highest dose group of the mixture and in the positive control. Liver, thymus, and spleen were the target organs of action. Microscopic changes in the liver consisted of vacuolation and hypertrophy, and those in the thymus were characterized by reduced cortical and medullary volume. The spleen showed a treatment-related reduction in lymphocyte density and lymphoid areas. This study demonstrates that exposure to the POP mixture up to 13 mg/kg/day perinatally produced growth suppression, elevated serum cholesterol, increased liver microsomal enzyme activities, and immunopathological changes in the thymus and spleen, and lethality. Most of the effects were seen at dose levels much higher than expected human exposure.

Subtle effects of low-dose exposure to environmental toxicants may be altered or masked by an inappropriate choice of anaesthesia prior to manipulation or termination of experimental animals. This study was designed to investigate effects of various anaesthetics and terminal procedures on neurotransmitters from male Sprague-Dawley rats. Significant changes in neurotransmitters were observed in the caudate nucleus, nucleus accumbens, hippocampus and substantia nigra but not the frontal cortex upon exposure to isoflurane, an Equithesin-like mixture or carbon dioxide relative to control animals that were decapitated without anaesthesia. Terminal use of any of these three anaesthetics also masked or altered some of the changes induced by exposure to Aroclor 1254. These results suggest that it is critical to avoid anaesthetizing experimental animals and that decapitation is the preferred method for euthanasia when conducting neurochemical studies.

The developmental and neurobehavioral effects of gestational and lactational exposure to a mixture of 14 polychlorinated biphenyls (PCBs) and 11 organochlorine pesticides was examined and compared against the commercial PCB mixture Aroclor 1254. The mixture was based on blood levels reported in Canadian populations living in the Great Lakes/St. Lawrence basin. Pregnant Sprague-Dawley rats were dosed orally with 0.013, 0.13, 1.3, or 13 mg/kg of the chemical mixture or 15 mg/kg of Aroclor 1254 from gestation day (GD) 1 to postnatal day (PND) 23. The highest mixture dose decreased maternal gestation and lactation body weight, and produced high mortality rates (80% overall) and reductions in offspring weight that persisted to adulthood. Aroclor 1254 produced smaller but persistent decreases in offspring weight without affecting maternal weight or offspring mortality. Aroclor 1254 and 13 mg/kg of the mixture produced comparable decreases in maternal and offspring serum T4 levels and comparable alterations to maternal thyroid morphology. Aroclor 1254 delayed the righting reflex and ear opening, accelerated eye opening, and reduced grip strength at PNDs 10-14. The mixture at 13 mg/kg delayed negative geotaxis in addition to delaying righting reflex and ear opening and reducing grip strength but had no effect on eye opening. Lower mixture doses (0.13 and 1.3 mg/kg) also delayed ear opening but affected no other parameters. Developmental exposure to the chemical mixture was found to be more toxic than exposure to Aroclor 1254 and produced a different profile of effects on early neurodevelopment. This PCB/organochlorine pesticide mixture affects mortality, growth, thyroid function, and neurobehavioral development in rodents.

The subchronic toxicity of dibromoacetonitrile (DBAN), a disinfection by-product in drinking water, was studied in the rat. Male (180+/-18 g) and female (152+/-9 g) Sprague-Dawley rats (10 animals per group) were fed DBAN in organic-free distilled water at concentrations of 0.1, 1, 10 and 100 ppm for 13 weeks. Control rats received organic-free distilled water only. Water intakes in the highest dose males and females were reduced by 25 and 32% as compared to the controls, respectively (P0.05), with no significant reductions in food consumption and body weight gain. The organ to body weight ratio was significantly increased in the highest-dose males and females for kidneys but not for the brain, liver, spleen, thymus and testicles. In the males, decreases were detected in serum uric acid levels at 1 and 100 ppm, and in urinary uric acid at 10 and 100 ppm. Decreased serum protein was detected in the highest-dose males and decreased serum LDH was found in the highest-dose females. Both the white blood cell and lymphocyte counts were significantly elevated in the highest-dose females. A significant increase in hepatic catalase activity was observed only in males starting at 1 ppm, and increased palmitoyl-CoA oxidase (PCO) activity was found in males and females of the highest dose group. In the males, decreased thiobarbituric acid reactive substance (TBARS) level was detected in the liver at 1.0 and 100 ppm groups, while increased TBARS was found in the serum at 100 ppm DBAN. No treatment-related changes were detected in the activities of hepatic benzyloxyresorufin O-dealkylase (BROD), pentoxyresorufin O-dealkylase (PROD) and ethoxresorufin O-deethylase (EROD), and in hepatic UDP-glucuronosyltransferase (UDPGT) and glutathione S-transferases (GST). Although DBAN is a potent inhibitor of hepatic aldehyde dehydrogenase (ALDH) and GST in vitro, there was no evidence of suppression of these enzymes in the treated animals. Mild histological changes were detected in animals receiving the highest dose, consisting of collapsed angularity, increased epithelial height in the thyroid of both sexes, and cytoplasmic vacuolation and nuclear vesiculation in the thyroid of females, increased myeloid to erythroid ratio in the bone marrow of both sexes, and cytoplasmic inclusions in the proximal tubules of male kidneys. In summary, treatment effects occurred predominantly at 100 ppm and included in both sexes: increased kidney weights, histological changes in the thyroid and bone marrow, and increased peroxisomal enzyme activities; and in males: decreased serum and urinary uric acid levels, and indication of oxidative stress. The no-observed-adverse-effect level (NOAEL) was therefore judged to be 10 ppm, equivalent to 1.11 and 1.21 mg/kg/day in the males and females, respectively.

This study aimed to increase the knowledge about the toxicity of fish-derived organohalogen pollutants in mammals. The strategy chosen was to separate organohalogen pollutants derived from Baltic herring (Clupea harengus) fillet, in order to obtain fractions with differing proportions of identified and unidentified halogenated pollutants, and to perform a subchronic toxicity study in rats, essentially according to the OECD guidelines, at three dose levels. Nordic Sea lodda (Mallotus villosus) oil, with low levels of persistent organohalogen pollutants, was used as an additional control diet. The toxicological examination showed that exposure to Baltic herring oil and its fractions at dose levels corresponding to a human intake in the range of 1.6 to 34.4 kg Baltic herring per week resulted in minimal effects. The spectrum of effects was similar to that, which is observed after low-level exposure to pollutants such as chlorinated dibenzo-p-dioxins and dibenzofurans (CDD/F) and chlorinated biphenyls, despite the fact that these contaminants contribute to a minor part of the extractable organically bound chlorine (EOCl). The study confirmed previous findings that induction of hepatic ethoxyresorufin deethylase (EROD) activity takes place at daily intake levels 0.15 ng fish-derived CDD/F-TEQs/kg body weight. The study also demonstrated that hepatic vitamin A reduction takes place at somewhat higher daily exposure levels, i.e. 0.16–0.30 ng fish-derived CDD/F-TEQs/kg body weight. Halogenated fatty acids, the major component of EOCl, could not be linked to any of the measured effects. From a risk management point of view, the study provides important new information of effect levels for Ah-receptor mediated responses following low level exposure to organohalogen compounds from a matrix relevant for human exposure.

The subchronic toxicity of chloral hydrate, a disinfection byproduct, was studied in rats following 13 weeks of drinking water exposure. Male (262 +/- 10 g) and female (190 +/- 8 g) Sprague-Dawley rats, ten animals per group, were administered chloral hydrate via drinking water at 0.2, 2, 20 and 200 ppm. Control animals received distilled water only. Gross and microscopic examinations, serum chemistry, hematology, biochemical analysis, neurogenic amine analysis and serum trichloroacetic acid (TCA) analysis were performed at the end of the treatment period. Bronchoalveolar fluids were collected at necropsy and urine specimens were collected at weeks 2, 6 and 12 for biochemical analysis. No treatment-related changes in food and water intakes or body weight gains were observed. There were no significant changes in the weights of major organs. Except for a mild degree of vacuolation within the myelin sheath of the optic nerves in the highest dose males, there were no notable histological changes in the tissues examined. Statistically significant treatment-related effects were biochemical in nature, with the most pronounced being increased liver catalase activity in male rats starting at 2 ppm. Liver aldehyde dehydrogenase (ALDH) was significantly depressed, whereas liver aniline hydroxylase activity was significantly elevated in both males and females receiving the highest dose. A dose-related increase in serum TCA was detected in both males and females starting at 2 ppm. An in vitro study of liver ALDH confirmed that chloral hydrate was a potent inhibitor, with an IC(50) of 8 micro M, whereas TCA was weakly inhibitory and trichloroethanol was without effect. Analysis of brain biogenic amines was conducted on a limited number (n = 5) of male rats in the control and high dose groups, and no significant treatment-related changes were detected. Taking into account the effect on the myelin sheath of male rats and the effects on liver ALDH and aniline hydroxylase of both males and females at the highest dose level, the no-observed-effect level (NOEL) was determined to be 20 ppm or 1.89 mg kg(-1) day(-1) in males and 2.53 mg kg(-1) day(-1) in females. This NOEL is ca. 1000-fold higher than the highest concentration of chloral hydrate reported in the municipal water supply.

Seven commercially available, structurally related azo dyes have been bioreduced by the anaerobic bacterium Clostridium paraputrificum. The rates of reduction of these dyes were found to vary between 24 and 74 nmoles reduced/mg protein/h. Acid red 1 and desmethyl acid red 106 were found to be the most readily reduced, while chromotrope 2R and cibacron brilliant red 3B-A were reduced at the slowest rates. The differences in reduction rates can be rationalized on the basis of structural differences and are consistent with the possible intermediacy of low molecular-weight electron carriers as the mediators of reduction. The incorporation of electron-withdrawing groups into the dyes, even if remotely placed, was found to increase the rate of reduction of dyes under controlled conditions, supporting the inversely proportional relationship between the electron density of the azo bond and the ease of bioreduction.

The biochemical and toxicological effects of chloral hydrate were investigated. Four groups (n = 7 per group) of male Sprague-Dawley rats (161-170 g) were administered chloral hydrate in drinking water at concentrations of 20, 200 or 2000 ppm for 7 days. The control group received phosphate-buffered water only. There were no treatment-related changes in the body weight gains, relative weights of major organs or haematological parameters. Trichloroacetic acid was significantly (P < 0.05) elevated in the serum of high-dose animals (7.75 +/- 5.14 mg dl(-1), mean +/- SD). In the high-dose animals there was a 36% increase in protein level in the liver homogenates but not in the corresponding 9000 g supernatants. Concurrently, there was a threefold increase in the activity of the hepatic peroxisomal enzyme palmitoyl CoA oxidase (PCO). A prominent change was the dose-related suppression in hepatic aldehyde dehydrogenase (ALDH) activity observed in all treatment groups, with the decrease ranging from 15% at 20 ppm to 68% at 2000 ppm. There were no significant decreases in the activity of hepatic enzymes ethoxyresorufin O-deethylase (EROD), benzyloxyresorufin O-dealkylase (BROD) and UDP-glucuronosyl-transferase (UDPGT). In the high-dose group there was a 30% increase in hepatic glutathione-S transferase (GST) activity, accompanied by a 13% increase in glutathione (GSH). Significant effects on lipids were observed in the liver of the high-dose animals, with a 15% decrease in hepatic cholesterol and triglyceride levels. There were no treatment-related changes in serum chemistry parameters, including cholesterol and triglyceride levels. Although in vitro assays showed chloral hydrate to be an inhibitor of serum pseudocholinesterase activity, with a 50% inhibition concentration (ic(50)( of approximately 0.7 mM at 5 mM butyrylthiocholine, no decrease in serum pseudocholinesterase activity was found in the treated animals. It was concluded that the liver is the target organ for chloral hydrate, with suppression of ALDH as the most sensitive endpoint followed by alteration in the GSH level and GST activity. Changes observed in the high-dose animals, such as increased peroxisomal PCO activity in the liver and perturbation of lipid homeostasis in the liver and blood, were likely to be associated with trichloracetic acid, the major metabolite of chloral hydrate.

The pH stability and acute oral toxicity of dimethoxymethane (DMM) in rats were studied. In in vitro studies, DMM was found to be stable in artificial gastric juice at pH 2.5 and above but readily hydrolyzed at pH 2 and below, with 1 mole of DMM producing approximately 1 mole of formaldehyde and 2 moles of methanol. DMM incubated in sealed, excised stomachs appeared to equilibrate with the external incubation fluid over a 24-hour period without significant hydrolysis. In the toxicity study, three groups of female rats ( n = 5) were administered, by gavage, phosphate-buffered saline (control), DMM (31 mmoles/kg body weight [bw]/day), or methanol (MeOH) (30 mmoles/kg bw/day), respectively, for 3 consecutive days and then sacrificed on day 5. Transient ataxia lasting about 30 minutes was observed in animals following DMM administration. Increased urine volume was observed in the DMM group at the end of days 4 and 5. Markedly elevated level of formic acid was present in the urine of the MeOH group at days 1, 2, and 3, but not in the DMM group. Urinary ascorbic acid levels were increased in the DMM group on days 1, 2 and 3, and returned to baseline level at days 4 and 5. Microscopic examination detected no abnormal histological changes in the liver and kidneys of MeOH-or DMM-treated animals. No treatment effects were observed on the following endpoints: organ weights (liver, heart, thymus, kidneys), serum corticosterone, serum chemistry profile, hematology, hepatic phase 1 and phase 2 mixed-function oxidase activities, hepatic and serum thiobarbituric acid, hepatic glutathione, urinary protein, and urinary N-acetylglucosaminidase activity. These observations suggested that hydrolysis of DMM in the stomach required a gastric acidity below pH 2.5. At higher pH, intact DMM readily penetrated the stomach and therefore likely reached the circulation and other body tissues. There was no significant hydrolysis of orally administered DMM, and the acute effects were limited to transient ataxia and biochemical responses in the liver.

The subchronic toxicity of 0.2-200 ppm dichloramine and 0.2-90 ppm trichloramine in the drinking water of rats was investigated using biochemical, hematological, and histopathological parameters. Animals in the highest dose groups consumed 5-15% less fluid than controls with no significant decrease in body weight gain. No clinical signs of toxicity were observed in either case. Both males and females dosed with 90 ppm trichloramine had significantly increased relative kidney/body weights and the females had increased hepatic glutathione S-transferase and UPD-glucuronosyltransferase activities. No significant changes were detected in other xenobiotic metabolizing enzymes or in serum biochemistry, urine biochemistry, or hematology. Both dichloramine and trichloramine induced minimal to mild adaptive histopathological changes in thyroids and kidneys of animals of both sexes. Dichloramine, but not trichloramine, was associated with histological changes in the gastric cardia characterized by epithelial hyperplasia at concentrations of 2 ppm and above in the males and 200 ppm in the females. This study indicates that dichloramine produced mild histological effects at drinking water concentrations of >0.2 ppm in males (0.019 mg/kg/day) and >2 ppm in females (0.26 mg/kg/day) while trichloramine produced biochemical and mild histological effects at levels of >2 ppm both in males (0.23 mg/kg/day) and in females (0.29 mg/kg/day).

Tris(4-chlorophenyl)methanol (TCPM) is a global contaminant of unknown origin that is structurally related to the endocrine modulating pesticides 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and Dicofol. Therefore, the potential reproductive toxic effects of TCPM were investigated in sexually mature male Sprague Dawley rats (n = 20) treated with 1.0, 10.0 or 100 ppm of TCPM mixed in the diet for 28 days. The calculated TCPM intake was 0.0, 0.1, 1.2 and 12.4 mg/kg/day, respectively. Serum concentrations of follicle stimulating hormone (FSH) in terminal blood samples were significantly (P < 0.02) elevated in the highest dose group compared to the controls. In contrast, dietary exposure to TCPM had no effect on circulating levels of luteinizing hormone (LH), testosterone (T) and the T/LH ratio. Incubation of MCF-7 cells with increasing concentrations of TCPM failed to either induce proliferation or to block the proliferative effect induced by estradiol indicating that TCPM is neither estrogenic or anti-estrogenic. Relative binding affinity studies using androgen receptors from the prostate revealed that TCPM has a binding affinity comparable to 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE), the principle metabolite of DDT. In addition, the calculated Ki (0.62 microM) for TCPM is lower than the reported Ki's for the antiandrogenic pesticides p,p'-DDE and vinclozolin. Although TCPM binds with the androgen receptor in vitro, the absence of both an effect on serum T levels and morphological changes in the testis suggests that the mechanism of action for elevated FSH levels seen in vivo may not involve an antiandrogenic effect of TCPM at the dose level used in this study. The no adverse effect level for reproductive effects of TCPM is 10 ppm which is equivalent to a calculated intake of 1.2 mg/kg/day.

Hepatocyte cytoplasmic alterations were morphometrically determined in male and female Sprague-Dawley rats fed PCB congener 126 (3,3',4,4',5-pentachlorobiphenyl) in concentrations of 0.1, 1.0, 10, 100 ppb or corn oil in diets for 13 weeks. A dose-dependent increase (P < 0.05) in the volume fraction of smooth endoplasmic reticulum (SER) and mitochondria was measured in the hepatocytes of the females. However, these cells of the male rats contained a significantly greater baseline volume fraction of SER compared to that in the females. Statistical differences were not detected in the volume fractions of rough endoplasmic reticulum, peroxisomes or lipid droplets of the hepatocytes in either the males or females. We conclude the increase in mitochondrial volume was a necessary cellular adaptation to meet the heightened energy demands by the SER to produce the necessary enzymes to detoxify the PCB. Morphometric analysis rather than a descriptive methodology allowed for a more accurate determination of the liver pathology induced by PCB 126.

The subchronic inhalation toxicity of a methanol/gasoline blend (85% methanol, 15% gasoline, v/v) was studied in rats. Sprague Dawley rats (10 animals per group) of both sexes were exposed to vapors of methanol/gasoline at 50/3, 500/30 and 5000/300 ppm for 6 hours per day, 5 days per week, for 13 weeks. Control animals inhaled filtered room air only. Control recovery and high dose recovery groups were also included which inhaled room air for an extra 4 weeks following the treatment period. No clinical signs of toxicity were observed in the treatment group and their growth curves were not significantly different from the control. Except for decreased forelimb grip strength in the high dose females, no treatment-related neurobehavioural effects (4-6 hours post inhalation) were observed using screening tests which included cage-side observations, righting reflex, open field activities, and forelimb and hindlimb grip strength. At necropsy, the organ to body weight ratios for the liver, kidneys, spleen, testes, thymus and lungs were not significantly different from the control group. There were no treatment-related effects in the hematological endpoints and no elevation in serum formate levels. Minimal serum biochemical changes were observed with the only treatment-related change being the decreased creatinine in the females. A dose-related increase in urinary ascorbic acid was detected in males after 2,4 and 8 weeks of exposure, but not after the 12th week, and in females only at week-2. Increased urinary albumin was observed in treated males starting at the lowest dose and at all exposure periods, but not in females. A treatment-related increase in urinary β 2-microglobulin was detected in males at week-2 only. Except for mild to moderate mucous cell metaplasia in nasal septum B, which occurred more often and with a slightly higher degree of severity in the low dose groups of both sexes, and presence of a minimal degree of interstitial lymphocyte infiltration in the prostate glands of the high dose males, no other significant microscopic changes were observed in the tissues of treated animals. Based on the marked increase in urinary ascorbic acid and albumin in the high dose males and the decreased forelimb grip strength in the high dose females, we concluded that the no-observed adverse effect level (NOAEL) of methanol/gasoline vapor is 500/30 ppm.

The toxicity of 2,3,3',4,4'-pentachlorobiphenyl (PCB 105) was investigated in Sprague-Dawley rats following dietary exposure to this substance at levels of 0, 0.05, 0.5, 5 or 50 ppm for 13 weeks. Growth rate and food consumption were not affected and no clinical signs of toxicity were observed. Increased incidences of enlarged, fatty liver and decreased thymic weight were observed in the highest-dose groups of both genders; these groups also had elevated hepatic microsomal ethoxyresorufin deethylase activity and uroporphyrin. Significant increases in serum cholesterol and hepatic pentoxyresorufin dealkylase activity were observed in the highest-dose males and two highest-dose females. By contrast, liver UDP-glucuronosyl transferase activity was elevated in the two highest-dose males and the highest-dose females. Urinary ascorbic acid excretion was increased in the highest-dose males. While the amount of vitamin A was decreased dose-dependently, starting at 0.5 ppm in the liver of both sexes and in the lung of the females, the level in the kidney of the highest-dose group was increased. Administration of PCB 105 resulted in decreased dopamine in the caudate nucleus region of the brain in males and homovanillic acid in caudate nucleus and nucleus accumbens of females. Increased 5-hydroxytryptamine and 5-hydroxyindoleacetic acid were observed in the substantia nigra region of both sexes, with most of the increases being seen in highest-dose females. Anemia, characterized by decreased hemoglobin, hematocrit and red cell indices, occurred in the highest-dose group, as did eosinophilia. Treatment with PCB 105 caused dose-dependent histopathological changes in the liver and thyroid. Thymic changes were observed in the highest-dose males and two highest-dose females. Tissue residue data showed a dose-dependent accumulation of this congener in fat, liver and spleen, kidney and brain. Based on these data the no-observable-effect level of PCB 105 was judged to be 0.05 ppm or 3.9 microg kg(-1) body wt. day(-1) in males and 4.2 microg kg(-1) body wt. day(-1) in females.

An automated static head space-gas chromatography method was used in the determination of partition coefficients (K d ) for the xylene isomers and ethylbenzene in blood, brain, muscle, kidney, liver and fat of Sprague Dawley rats. Since homogenization resulted in the potential loss of analytes from tissue samples, unhomogenized samples were used. With a few exceptions, tissue: air K d values were independent of the concentrations of the analytes, singly or as a mixture. The tissue:blood K d values were determined. For each tissue and analyte, the value obtained for each analyte concentration was within ± 10% of the mean value calculated for the entire concentration range.

Groups of 4 male Wistar rats were dosed intravenously with 14C-labeled benzo[a]pyrene dissolved in an Emulphor/water vehicle at 3 different dose levels and killed at 1 of 15 specific time intervals from 5 min to 32 h after dosing. 14C-Radiolabel concentration-time data were obtained for blood, brain, adipose, heart, kidney, liver, lung, spleen, and testes. Benzo[a]pyrene concentration-time data were obtained for blood, adipose, kidney, liver, and lung. Appropriate mathematical models were fitted to these data and to the data for metabolites derived as the residuals from 14C-radiolabel minus benzo[a]pyrene difference, where applicable. Nonlinear kinetics were found for 14C-radiolabel in liver, while the data from lung for both 14C-radiolabel and for benzo[a]pyrene per se supported the binding of benzo[a]pyrene in that tissue.

Subchronic exposure to the PCB congener 77 (PCB 77) and 28 (PCB 28) was previously shown to induce histological changes in the thyroid and in the brain biogenic amines levels, suggesting possible effects on thyroid and reproductive hormone levels. Thus, the effects of a 90-day dietary exposure to PCB 28 or 77 on luteinizing hormone, follicle-stimulating hormone, and testosterone concentrations were studied in male rats, as well as the levels of thyroid-stimulating hormone, thyroxine (T4) and uridine diphosphate-glucuronyl transferase (UDP-GT) activity in both genders. Weanling Sprague Dawley rats were randomly distributed into groups of 10 rats and were fed, for the next 13 weeks, purina lab chow containing 50, 500, 5000, or 50 000 ppb of PCB 28 or 10, 100, 1000, or 10 000 ppb of PCB 77. The serum concentrations of T4 were decreased in rats of both sexes receiving 1000 ppb or more of PCB 77, and was associated with an increased activity of UDP-GT which reached significance only in the females. There was a tendency for the highest dose of PCB 28 also to decrease serum T4 concentrations in the female rats. None of the PCB treatments significantly altered gonadotropin, TSH, or testosterone concentrations. These results suggest that thyroid functions may be more susceptible or adapt less readily than the pituitary gland and the testes to endocrine disruption caused by PCB congeners.

The in vitro penetration of [14C]benzene through freshly prepared human skin was examined under a variety of skin conditions associated with swimming and bathing. The experimental system utilized a recirculating donor solution and a flow-through receiver solution, and was modified to accommodate the analysis of volatiles. The permeability coefficient of 0.14 cm/h under standard conditions at 26 degrees C was found to increase to 0.26 cm/h at 50 degrees C and decrease to 0.10 cm/h at 15 degrees C. Storage of the skin at- 20 degrees C did not affect the penetration of benzene. Application of baby oil, moisturizer, or insect repellant to the skin before exposure under standard conditions did not affect the flux of benzene, but a significant increase was observed when the skin was pretreated with sunscreen (permeability coefficient 0.24 cm/h). These results suggest that risk assessment or exposure modeling for benzene and other environmental contaminants should account for appropriate changes in the environmental conditions when considering the dermal route of exposure.

The subchronic toxicity of acridine was investigated in rats following dietary exposure at 0, 1, 10, 100 and 500 ppm for 13 weeks. The growth rate and food consumption were not affected by treatment and no clinical signs of toxicity were observed. There was a slight but significant decrease in spleen weight, both in absolute terms and as a percent of body weight, in the 500 ppm males and a slight increase in absolute thymus weight in the females of the same dose group. Both hepatic ethoxyresorufin O-deethylase (EROD) and pentoxyresorufin O-dealkylase (PROD) activities were slightly, but significantly, elevated in females in the 500 ppm dose group. No haematological or other biochemical changes were observed. Females also displayed dose-related increases in inorganic phosphate and uric acid levels. Treatment-related histopathological changes were seen in the thyroid, liver and kidney and included hepatic anisokaryosis and vesiculation of nuclei and glomerular adhesions, reticulin sclerosis and nuclear pyknosis in the kidney. Residue data showed a dose-dependent accumulation of acridine in liver, kidney and adipose with the highest concentration being found in the fat of the 500 ppm dose group. Based on these data, the no observable adverse effect level of acridine was judged to be 100 ppm or 12 mg/kg bw/day.

A database on physicochemical properties and skin permeation compiled by Health Canada was analysed by using linear regression analysis. The correlation between permeability coefficient (Kp) and the octanol–water partition coefficient (Kow) has been improved by grouping the compounds according to their respective molar volumes. Linear regression analysis of the individual groups has demonstrated a positive correlation for the majority of the groups, with the compounds in the lowest molar volume range (≤ 75Å3) having the best correlation (r2 = 0.86), and the compounds in the highest molar volume range (≥ 30lÅ3) being the least well-correlated (r2 = 0.55). Due to the diversity of the chemicals used in this analysis, and the statistically significant correlations obtained, this model could permit the prediction of skin permeation of a wide variety of chemical compounds. Although of a simplistic nature, and not yet experimentally validated, this quantitative structure-activity relationship may be useful for predicting human skin permeability coefficients for compounds that fall within the constraints of this data set.

The subchronic oral toxicity of di(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DNOP) was studied. Groups of 10 male and 10 female Sprague-Dawley rats were administered DEHP in the diet at 0, 5, 50, 500 or 5000 ppm for 13 wk. In a separate study, groups of 10 male and 10 female Sprague-Dawley rats were given DNOP (5, 50, 500 and 5000 ppm) in the diet while control groups received basal diet containing 4% corn oil and positive control groups were fed a diet containing 5000 ppm DEHP. Growth rate and food consumption were not affected by treatment with either compound. Hepatomegaly was observed in the highest dose groups of both sexes administered DEHP but not in the DNOP-treated animals. At the highest dose, DNOP caused threefold (females) and 12-fold (males) increases in liver ethoxyresorufin-O-deethylase activity while DEHP did not. Mild changes in serum biochemistries were mostly confined to rats in the highest dose group of DEHP, and included increased serum albumin and albumin/globulin ratio in both sexes and decreased cholesterol in female rats. Mild vacuolations in the Sertoli cells were observed in male rats exposed to 500 ppm DEHP. At 5000 ppm DEHP, there was mild to moderate seminiferous tubule atrophy and Sertoli cell vacuolation in males, and rats of both sexes showed hepatic peroxisome proliferation. Both DEHP and DNOP at 5000 ppm caused mild histological changes in the thyroid consisting of reduced follicle size and colloid density, and the liver consisting of endothelial nuclear prominence, nuclear hyperchromicity and anisokaryosis. There was accentuation of zonation of the hepatic lobules and increased perivenous cytoplasmic vacuolation in DNOP-treated rats. Trace quantities (3-5 ppm) of DEHP and DNOP were detected in the liver, and 15-31 ppm were found in adipose tissue of the highest dose groups. The no observed-effect-level was judged to be 50 ppm in the diet or 3.7 mg/kg body weight/day for DEHP, and 500 ppm or 36.8 mg/kg body weight/day for DNOP.

The systemic toxicity of benzothiophene, a sulfur-containing heterocyclic present in petroleum, coal, and their derived products, was studied in male rats following short-term oral exposure. Male Sprague-Dawley rats (130 +/- 20 g) (n = 5 per dose group) were treated with benzothiophene by gavage at dosages of 0, 2, 20 or 200 mg/kg/d for 21 d. In another study, male rats were treated with 0, 100, or 500 ppm benzothiophene via the diet for 28 d. In the gavage study, the 200 mg/kg/d rats showed depressed weight gain, increased relative liver and kidney weights, decreased relative thymus weights, and elevated levels of serum gamma-glutamyltransferase (gamma-GT), hepatic aniline hydroxylase (AH), aminopyrine N-demethylase (APDM), pentoxyresorufin O-dealkylase (PROD), glutathione S-transferase (GST), and UDP-glucuronosyltransferase (UDPGT) activities. A 4.5-fold increase in urine volume on d 14-21 and a transient, 4-fold increase in urinary ascorbic acid on d 1 were also detected. No treatment related changes in urinary N-acetylglucosaminidase (NAGA) activity were observed. Benzothiophene residues were not detected in adipose tissue, liver, and serum of rats in the 200 mg/kg rats, but a small quantity was detected in the urine. In the diet study, animals fed the 500 ppm diet had increased absolute and relative liver weights, elevated AH, APDM, and GST activities, decreased red blood cell count, and minor increases in serum urea nitrogen and glucose. In summary, benzothiophene produced adverse effects in male rats that included increased relative liver and kidney weights and increased urine output. Benzothiophene also caused increases in hepatic drug metabolizing enzyme activities of a phenobarbital type and a transient elevation in urinary ascorbic acid.

The systemic toxicity of tris(4-chlorophenyl)methanol (TCPM) was studied in male and female rats following 4 weeks dietary exposure dosed at 1, 10 and 100 ppm. An increased spleen to body weight ratio was observed in males at 10 and 100 ppm and in females at 100 ppm. An increased liver to body weight ratio was detected in both sexes at 100 ppm. Dose-related increases in hepatic Phase-I (AH, APDM, EROD and PROD) and Phase-II (UDPGT, GST) enzyme activities were observed generally at 10 and 100 ppm, with the elevation in PROD activity being the most marked. Increased urinary ascorbic acid was detected in both males and females after 1 week of treatment at 100 ppm and after 4 weeks of treatment at 10 and 100 ppm. At 10 and 100 ppm, elevated % lymphocytes were found in males, and higher white blood cell and lymphocyte counts were observed in females. In the liver, mild to moderate cytoplasmic changes consistent with proliferation of smooth endoplasmic reticulum were present in rats of both sexes at 10 and 100 ppm, and increased number of hepatocytes undergoing apoptosis were observed in male rats at 100 ppm. Mild splenic changes consisting of sinus hyperplasia in males and females at 100 ppm and mantle zone atrophy in males at 100 ppm were also observed. It was concluded that TCPM at a dietary concentration of 10 ppm (equivalent to 1.2 mg/kg/day) produced systemic changes in rats that included various hepatic effects, increased splenic weight, and modulations in white blood cells and lymphocyte counts.

The subchronic toxicity following dermal exposure to a synthetic fuel, heavy gas oil No. 2 fraction of bitumen upgrading product (B-HGO II) was studied in the rat. B-HGO II was applied on the dorsal skin of rats at doses of 8, 20, 50 and 125 mg/kg bw/day daily for 13 weeks. Control animals received normal saline and positive controls received a medium-boiling coal liquefaction product (CLP) at 125 mg/kg bw/day. Both male and female rats in the treatment groups had reduced body weight gain, and males in the highest dose group were terminated in the 5th week due to overt toxicity. Increased liver weight relative to body weight was observed in males and females starting at 8 mg/kg. Increased relative heart and spleen weights were observed in males and females starting at the two intermediate doses (20, 50 mg/kg). Increased relative kidney weight was detected in males at 50 mg/kg and females at 125 mg/kg. Increased serum cholesterol was observed in both sexes starting at 50 mg/kg while elevated serum glucose was present in females starting at 8 mg/kg. Significant changes in AH, APDM and EROD activities were observed in treated rats of both sexes. Reduced red blood cell counts were detected in males starting at 8 mg/kg and females at 20 mg/kg. Microscopic examination of blood smears, spleen and hemosiderin accumulation patterns, as well as analysis of FEP and serum TIBC levels indicated that the cause of anemia was primarily intravascular hemolysis and secondarily iron deficiency. Marked thymic atrophy and thyroid abnormalities were the most prominent histological changes followed by changes in bone marrow (myelofibrosis) and liver. Both B-HGO II and CLP (positive control) caused kidney changes characterized by cytoplasmic inclusions and lesions in the tubular cells, which were observed in 50 mg/kg males but not in the females. B-HGO II was considered to be toxic at a subchronic dermal exposure level as low as 8 mg/kg/day.

The subchronic toxicity of 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) was investigated in rats after 13 weeks of dietary exposure. Groups of 10 male and 10 female rats were administered PCB 153 in their diet at levels of 0.05, 0.50, 5.0 or 50 ppm for 13 weeks. The control groups received the diet containing 4% corn oil. Growth rate and dietary consumption were not affected by treatment. Clinical signs of toxicity were not observed. Enlarged, fatty liver was observed in treated animals at necropsy, but most were confined to the two highest dose groups. Increased hepatic microsomal ethoxyresorufin-O-deethylase, aminopyrine-N-demethylase and aniline hydroxylase activities occurred in high-dose groups of both sexes, with increased ethoxyresorufin-O-deethylase activity being observed starting at 0.05 ppm in females and at 0.5 ppm in males. Treatment-related reduction in hepatic and pulmonary vitamin A was seen in the highest dose group of both sexes. Changes in brain biogenic amines and intermediate products were observed mainly in females; these included decreased dopamine and 5-hydroxytryptamine concentrations in the frontal cortex region, and dihydroxyphenylacetic acid in the caudate nucleus region at 5.0 and 50 ppm. Female rats appeared to be more sensitive to the neurotoxic effects of PCB 153 than males. Dose-dependent histological changes were observed in the thyroid and liver of rats of both sexes and significant changes occurred at 5.0 and 50 ppm. Based on these data, the no-observable-adverse-effect level (NOAEL) of PCB 153 was judged to be 0.5 ppm in the diet or 34 micrograms kg-1 body wt. day-1.

There is concern as to whether dermally applied chemicals that remain in the skin after exposure are bioavailable and should be included as part of the systemic dose; this study was conducted to investigate the temporal relationship between the skin depot and absorbed dose. Single doses of 14C-labelled phenanthrene, benzo[a]pyrene or di(2-ethylhexyl) phthalate were administered dermally to groups of four female, Hartley hairless guinea pigs which were housed individually in metabolism cages to collect urine and faeces for radioassay. The animals were sacrificed at 6 hr, 24 hr, 48 hr, 7 days or 14 days after dosing to harvest skin specimens for the determination of radioactivity by autoradiographic and liquid scintillation methods, and to determine the dose that remained in the body. It was found that for all three compounds the amount of chemical left in the skin decreased over time while the cumulative percent dose excreted in urine and faeces increased. The autoradiographic results were consistent with those obtained from the liquid scintillation method showing a gradual decrease in radioactivity grain accumulation over the time periods for the three compounds, with the highest grain density observed around hair follicles of the skin. The results of this study indicate that the chemicals left in the skin after surface washing eventually enter the systemic circulation and should be considered as part of the total dose absorbed, and that the hair follicle may play an important role in percutaneous penetration.

The present study was conducted as part of a larger project to determine the toxicity of dermally applied coal coprocessing products. Groups of male and female rats were administered, dermally, heavy gas oil II (HGOII) at 8.7, 20.8, 50.0 and 120 mg kg(-1) body wt, day(-1) for 91 days. A coal liquefaction product was given as positive control at 120 mg kg(-1) body wt. day(-1). Saline was used on control animals. At termination, the blood and bone marrow were taken from the animals and subjected to hematological examination. Dose-dependent hematological effects were seen in peripheral blood in HGOII-treated animals and consisted of significantly reduced hemoglobin, hematocrit, red cell count and platelet count. Mean corpuscular volume was increased, along with mean corpuscular hemoglobin, at the highest dose level. Red cell protoporphyrin, total iron and total iron binding capacity were also significantly elevated at this dose level. Morphological analysis of blood showed increases in polychromatic red cells, schizocytes, Howell-Jolly bodies, injured cells, hypersegmented neutrophils and shift platelets primarily at the highest dose level. In addition, there was notable anisocytosis, microcytosis and macrocytosis. Quantitative bone marrow evaluation revealed a significant reduction in the myeloid/erythroid ratio for the three highest treatment levels of HGOII. These data indicate that the effect of HGOII on the hemopoietic system is a treatment-related, partially compensated, hemolytic anemia. The apparent reduction in myelopoiesis may be compensated for by a concurrent increase in marrow volume.

The toxicity of 3,3',4,4'-tetrachlorobiphenyl (PCB 77) and 2,3',4,4',5-pentachlorobiphenyl (PCB 118) was investigated in rats following subchronic dietary exposure. Groups of 10 male and 10 female weanling Sprague-Dawley rats were administered PCB 77 in the diet at 0, 10, 100, 1000, or 10,000 ppb for 13 weeks. PCB 118 was administered to males in the diet at 0, 10, 100, 1000, and 10,000 ppb, while the female groups received 0, 2, 20, 200, or 2000 ppb of the congener for 13 weeks. Growth rate and food consumption were not affected by treatment. No clinical signs of toxicity were observed. Increased spleen weight occurred in male rats fed 1000 or 10,000 ppb PCB 77. Male rats receiving 10,000 ppb PCB 118 had increased liver weight and hepatic ethoxyresorufin O-deethylase (EROD) activity. Increased hepatic EROD activity but not liver weight was observed in female rats given the 2000-ppb PCB 118 diet. Increased EROD activity was also noted in male rats given 10,000 ppb and in female groups receiving 1000 or 10,000 ppb PCB 77. Male rats exposed to 10,000 ppb PCB 77 had decreased vitamin A in the liver and lung and elevated levels in the kidney. Liver vitamin A of both 1000- and 10,000-ppb PCB 77 female groups was decreased. PCB 118 had no effects on tissue vitamin A at the levels studied. No hematological changes or serum biochemical changes were seen in any of PCB 118- and PCB 77-treated groups, nor were liver uroporphyrin levels altered. A reduction in dopamine and homovanillinic acid in substantia nigra region of the brain was observed in female rats fed 2000 ppb PCB 118, while 10,000 ppb PCB 77 was associated with an elevation in 3,4-dihydroxyphenylacetic acid in the nucleus accumbens region of male rat brains. Mild to moderate changes were observed in the liver and thyroid of rats given PCB 77 or PCB 118. PCB 118 accumulated in a dose-dependent manner in fat and to a much lesser extent in liver. In contrast, very low levels of PCB 77 residue were found in the tissues examined. Based on the above data it was concluded that NOAEL of PCB 77 is 100 ppb in diet or 8.7 micrograms/kg and that of PCB 118 is 200 ppb in diet or 17 micrograms/kg body wt/day.

In vitro dermal absorption tests were conducted with the (14)C-ring-labelled pesticide, 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) dissolved in acetone and applied to dermatomed skin (0.5 mm) of a number of species at dose rates of 16-27 mug/cm(2). Skin absorption was determined for 48 hr after exposure using in vitro flow-through cells. Skin absorption was calculated from the sum of the percentage recovery of (14)C activity in the receiver solution added to the percentage recovery for the methanol washes of the skin at 48 hr and the skin digest samples. Two receiver solutions, Ringer's saline (used with Moody aluminium cells), and Hanks' HEPES buffered saline with 4% serum albumin (used with Bronaugh flow-through cells) were used. Listed in decreasing order, the total percentage in vitro dermal absorptions obtained by 48 hr after exposure for the five skin types were: 42 +/- 2.6% [hairless guinea pig; Hanks' receiver (HR)], 34 +/- 10.5% (rat; HR), 28 +/- 13.2% [Testskin; Ringer's receiver (RR)], 28 +/- 2.9% (human; HR), 22 +/- 3.3% (Testskin; HR), 18 +/- 6.2% (pig; RR) and 14 +/- 2.1% (pig; HR). The percentage (14)C activity recovered in soapy water rinses of the skin specimens at 24 hr, and for methanol skin washes and skin digests at 48 hr, and of (14)C-labelled volatiles collected in air traps are reported. Data obtained with pig and Testskin for DDT using the Moody flow-through permeation cell was compared with that obtained using the Bronaugh cell. Significantly greater (P0.05) percentage recovery was obtained for the soap washes at 24 hr of the skin following the Bronaugh procedure than was obtained with the Moody method. Comparative in vivo studies demonstrated urinary recovery was 2 +/- 0.5 and 15 +/- 1.7% for rats (dose rate; 6 mug/cm(2)) and guinea pigs (dose rate: 9 mug/cm(2)), respectively. Total faecal recovery was 20 +/- 1.9 and 44 +/- 2.75% for rats and guinea pigs, respectively. Analysis of tissue taken at autopsy 14 days after dosing demonstrated total tissue recovery of 51 +/- 5.6% in rats but of only 3 +/- 0.7% in guinea pigs. Including the (14)C activity extracted from the skin removed from the dose site at 14 days after exposure, the total recovery of dermally absorbed residues was 73 +/- 5.9 and 62 +/- 4.1% for rats and guinea pigs, respectively. Recovery of (14)C from soapy water skin washes conducted at 24 hr after exposure was 3 +/- 1.4 and 14 +/- 1.8% for rats and guinea pigs, respectively, and this was significantly less than that obtained by both the Bronaugh and Moody in vitro procedures. Skin patch recovery was 24% for both rats and guinea pigs. In summary, the in vitro data underestimed the degree of dermal absorption observed in vivo for both rats and guinea pigs, and this was thought to be due to an overly vigorous removal of the pesticide skin deposit by the soap washing procedures used in vitro in comparison with the in vivo washing procedure.

In vitro dermal absorption tests were conducted with the (14)C-ring-labelled herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), dissolved in acetone and applied to dermatomed skin (0.5 mm) of a number of species at dose rates of 7-8 mug/cm(2). Skin absorption was determined for 48 hr after exposure using an in vitro flow-through system. Skin absorption was calculated from the sum of the percentage recovery of (14)C activity in the receiver solution and the percentage recovery in the methanol washes of the skin at 48 hr and the skin digest samples. Two receiver solutions, Ringer's saline, and Hanks' HEPES buffered saline with 4% serum albumin were used. Listed in decreasing order, the total percentage in vitro dermal absorptions obtained by 48 hr after exposure for the five skin types were: 47 +/- 4.3% [tissue cultured Testskin; Hanks' receiver (HR)], 40 +/- 4.5% (rat; HR), 19 +/- 1.8% (human; HR), 14 +/- 2.3% (hairless guinea pig; HR), 14 +/- 8.8% (pig; Ringer's receiver). The percentage recovery of the radiolabel in soapy water skin washes at 24 hr, methanol washes and skin digests at 48 hr, and of (14)C-labelled volatiles collected in air traps at 48 hr after exposure are reported. Comparative in vivo studies were conducted for 14 days after exposure and demonstrated 32 +/- 3.9 and 28 +/- 7.8% recovery of (14)C in the urine of rats (dose rate, 3 mug/cm(2)) and guinea pigs (dose rate, 4 mug/cm(2)), respectively. Total faecal recovery was 2 +/- 0.3 and 9 +/- 3.5% for rats and guinea pigs, respectively. Analysis of tissue taken at autopsy 14 day after dosing demonstrated a total tissue recovery of (14)C activity of 1 +/- 0.1 and 2 +/- 0.5% in rats and guinea pigs, respectively. Including the (14)C activity extracted from the skin removed from the dose site at 14 days after exposure, the total recovery of dermally absorbed residues was 49 +/- 10.4 and 40 +/- 9.9% in rats and guinea pigs, respectively. Recovery of (14)C activity from soapy water skin washes conducted at 24 hr after exposure was 28 +/- 8.1 and 43 +/- 9.0% for rats and guinea pigs, respectively. Recovery in skin patches was 18% (guinea pigs) and 26% (rats). In summary, the in vitro/in vivo concordance for the rat dermal absorption data was good but the in vitro data for hairless guinea pigs underestimated the in vivo absorption, and therefore for 2,4-D, rat skin may provide a better model of percutaneous absorption.

A high-performance liquid chromatograph (HPLC) procedure has been developed for the determination of rat urinary ascorbic acid, a major metabolite of the hepatic glucuronic acid pathway. The presence of EDTA and HCl effectively inhibited degradation of ascorbic acid during the collection of urine specimens. The reliability of the procedure was demonstrated by its high recovery (90%), specificity (characteristic absorption maximum and discrimination from isoascorbic acid), and reproducibility (2-3% coefficient of variation). The usefulness of this assay as an indicator of hepatic response was demonstrated in preliminary experiments where increases in urinary ascorbic acid excretion were detected in male rats treated with PCB 126 (3,3',4,4',5-pentachlorobiphenyl) or PCB 105 (2,3,3',4,4'-pentachlorobiphenyl). The HPLC measurement also showed that the two PCB congeners differed markedly in their potency in stimulating urinary ascorbic acid excretion. For example, 10 micrograms/kg bw/day of PCB 126 was sufficient to cause a fourfold increase in urinary ascorbic excretion while 5000 micrograms/kg bw/day of PCB 105 was required for a sevenfold increase. In response to the administration of PCB 105 or PCB 126, urinary ascorbic acid appeared to increase to the same extent as increases in hepatic ethoxyresorufin O-deethylase (EROD) and UDP-glucuronosyltransferase (UGT) activities, and to a much higher extent than changes in liver weight and hematological and serum clinical chemical parameters. The sensitivity and specificity, the ease in obtaining timed specimens, and the noninvasive nature make this assay a useful biomarker of hepatic response in dose-finding and various acute and chronic studies.

Repeated exposure to coal liquefaction products produces a broad range of systemic effects. Among these, growth suppression, anaemia, leucocytosis and other haematological disorders are most prominent. Bone marrow, liver and kidney are the target organs affected by treatment. The effects are more severe with heavy distillates and male rats are more sensitive than females. Other changes included increased serum transaminases, alkaline phosphatase and cholesterol. Depending on the route of administration, the skin or lung may also be affected. Inhalation exposure produces the most severe changes, and oral exposure the least. Distillates containing N-PAHs and sulphur-containing PAHs are also more biologically active. Teratological effects were only observed if animals were exposed to the heavy distillate. Similarly, heavy distillates have mutagenic or carcinogenic properties. Teratological effects, as well as mutagenicity and carcinogenicity, of the coal liquefaction distillates seem to be linked to their PAH content, especially the N-PAHs. From the data presented in this review, it should become evident that the potential effects of coal liquefaction products on human health could be severe, especially with long-term exposure. Limited information exists on the occupational effects to coal liquefaction materials because most of the work to date has been with pilot plants. Careful and good judgement is required in order to extrapolate data from pilot plants to commercial-scale production. Experience in health effects of workers in the petroleum industry and coke-oven operations can serve as a guide for the implementation of industrial hygiene programmes for coal liquefaction operations. These programmes include engineering controls, health education, personal monitoring and hygienic practices, medical surveillance and long-term epidemiology studies, and they should be implemented to make coal liquefaction a healthy and environmentally sustainable industry.

The objective of the present study was to assess the potential interactive effects of two Great Lakes chemical contaminants, hexachlorobenzene (HCB) and mercury (HgCl2). Groups of 10 female Sprague-Dawley rats were administered by gavage single doses of HCB (400, 600 mg/kg b.w. in corn oil), HgCl2 (10.0, 12.5 mg/kg b.w. aqueous) or combinations of both followed by observation for clinical signs of toxicity for 14 days. Five animals from treatment groups died before the termination of the study; one animal each in 600 mg HCB, 400 mg HCB + 10 mg HgCl2, and 600 mg HCB + 10 mg HgCl2, and two animals in 600 mg HCB + 12.5 mg HgCl2. The surviving animals were necropsied at the termination of the study, and hematological, clinical chemistry, histopathological and tissue residue analyses were performed. Relative liver weights were increased in both low and high dose groups of HCB but not in animals treated with HgCl2 alone. Co-administration of HgCl2 did not alter the HCB effects on the liver weight of the animals. Serum cholesterol levels were increased in all the groups receiving HCB but not HgCl2. No interactive effects on other serum parameters were seen in animals administered with both chemicals. Mild to moderate morphological changes occurred in the liver, thyroid, thymus, ovary and bone marrow of rats exposed to HCB or HCB+HgCl2, and in the kidney of HgCl2 or HgCl2+HCB treated animals. More severe histological changes occurred in the groups receiving both chemicals. The histological effects appeared to be additive. It was concluded that co-administration with HCB and HgCl2 resulted in additive effects in some of the endpoints measured but no synergism or antagonism was observed.

The systemic toxicity of a coal coprocessing product [heavy gas oil II (HGOII)] following subchronic, dermal exposure in male Sprague-Dawley rats was investigated. HGOII was applied to the dorsal skin daily at doses of 8.7, 20.8, 50.0, or 120.0 mg/kg body weight (bw) for 13 weeks. Another group of rats treated with a medium boiling coal liquefaction product (CLP) served as positive controls. Growth suppression and decreased food consumption were noted in the groups exposed to HGOII at 20.8 mg/kg and higher, and to CLP starting at the third week of treatment. Relative liver, kidney, and brain weights in the 20.8 mg/kg HGOII group and up were higher than those of the control. Increased spleen weight was observed in all HGOII-treated groups. CLP treatment also caused increased relative kidney and brain weights. Serum cholesterol was elevated in the HGOII-treated groups starting at 8.7 mg/kg while increased uric acid and lactate dehydrogenase were observed at 20.8 mg/kg and up. Decreased erythrocyte, hemoglobin, and platelet counts were observed at 20.8 mg/kg and higher. All HGOII-treated groups had elevated reticulocytes. These biochemical and hematological changes were not observed in the CLP-treated group. Mild to marked histological changes were observed in the thyroid, thymus, liver, spleen, and bone marrow of HGOII groups. In contrast, morphological changes were relatively mild in CLP-treated animals. Data from the present study demonstrated that the hematological endpoints were sensitive to the liquid fuels and that HGOII was more toxic than CLP. Based on the growth rate and biochemical, hematological, and morphological changes, the no observable adverse effect level for HGOII is judged to be below 8.7 mg/kg bw in the rat.

Dermal absorption of heavy metal soil contaminants was tested in vitro with chloride salts of radioactive nickel (Ni-63) and mercury (Hg-203). Aqueous soil suspensions, spiked with either Ni-63 or Hg-203, were applied to fresh viable human breast skin tissue in Bronaugh diffusion cells perfused with Hanks HEPES buffered (pH 7.4) receptor containing 4% bovine serum albumin (BSA). Receptor fractions were collected every 6 h for 24 h when skin was soap washed. Tests were conducted concurrently in triplicate with and without soil for each skin specimen. Mean percent dermal absorption including the skin depot for Ni-63 was 1 and 22.8% with and without soil, respectively, while for Hg-203, values of 46.6 and 78.3% were obtained. Excluding the skin depot and considering only absorption in receptor, there was 0.5 and 1.8% absorption of Ni-63 with and without soil, respectively, and 1.5 and 1.4% for Hg-203. The potential bioavailability of the skin depot is discussed in relation to dermal exposure to these metals in contaminated soil.

The present study was conducted to determine the dermal toxicity of coal coprocessing products and to assess their potential health hazards. Groups of 10 male and 10 female Sprague-Dawley rats were administered dermally coal coprocessing products (light gas oil, LGO; heavy gas oil I, HGOI; heavy gas oil II, HGOII) at 1 g/kg body weight/d for 14 d. The control and positive control groups received normal saline and a coal liquefaction product (CLP) at the same dose level, respectively. Treatment with either the three fractions of coprocessing products or CLP caused decreased growth rate and food consumption in animals of both sexes. Liver enlargement occurred in groups treated with HGOI, HGOII, and CLP. Decreased serum glucose was observed in animals of both sexes treated with the three fractions and CLP. Treatment with HGOI and CLP caused an elevation of hepatic microsomal ethoxyresorufin deethylase activity in the rat of both sexes. The three fractions and CLP caused mild anemia. Mild treatment-related histological changes were observed in the liver, spleen, thyroid, bone marrow, and kidney. All three fractions of coprocessing products were tested for their mutagenicity in five strains of Salmonella typhimurium: TA98, TA100, TA1535, TA1537, and TA1538. HGOI, after metabolic activation, was found to be mutagenic in the strains of TA98, TA100, and TA1538. In contrast, HGOII was mutagenic in the five strains with or without metabolic activation. These data indicate that HGOI and HGOII are more toxic than LGO, and should be subjected to further studies to determine their long-term effects.

Although human populations are continuously exposed to complex mixtures of contaminants, the effects of such exposure on the developing brain transcriptome are poorly characterized. Rats were exposed perinatally to the northern contaminant mixture (NCM) which was designed to reflect the blood contaminant profile of Canadian arctic populations, to components of the NCM administered separately (methylmercury (MeHg), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCs)) or to the goitrogen propylthiouracyl. Post-natal day (PND) 14 cerebellum global gene expression resulting from such exposures was investigated using high-density cDNA microarrays. Fifty known genes were identified as differentially expressed between the control group and at least one other treatment group. The microarray data were validated by quantitative PCR (qPCR) on a subset of 10 genes. The differentially expressed genes are involved in a variety of processes, including nerve cell differentiation, migration, myelination and synaptic transmission. The comparison of cerebellum gene expression profiles resulting from exposure to the NCM and its individual components in male and female pups revealed that (i) gender is a crucial biological variable influencing genomic response to environmental contaminants and (ii) contaminant co-exposure significantly masks the effects of individual mixture components on cerebellum gene expression.