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The genetic modified Pseudomonas fluorescens Br 12, resistant to kanamycin and rifampycin, was used to follow the cotransport of the organochlorine acaricide dicofol through a nonsterilized soil column. P. fluorescens was found to bioaccumulate dicofol with the highest bioconcentration factor of 279 within 30 min. Separate soil column experiments where applied P. fluorescens or [14C]dicofol were submitted to heavy rain simulation did not reveal any correlation between the distribution patterns of P. fluorescens and [14C]dicofol in the leachate fractions (r = 0.3). Similar experiments with P. fluorescens that previously had bioaccumulated [14C]dicofol demonstrated a high correlation of these bacteria and radioactivity in the leachate fractions (r = 0.8). The total recovery of radioactivity in the leachate, when [14C]dicofol was previously bioaccumulated in bacteria, was more than two times higher (4.5%) than the total recovery of radioactivity in the leachate when [14C] dicofol was directly applied in the soil (2%). This indicates cotransport by Pseudomonas. Fractionation and analysis of soil columns indicated that most of the bioaccumulated dicofol was rapidly released and adsorbed in soil, while bacteria moved down by leaching.

The marked species differences in short-term toxicity (30-day LD50) of ca. 10,000 (LD50: guinea pigs ca. 1 microgram/kg body wt and Han/Wistar Kuopio rats more than 9600 micrograms/kg body wt) of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is one of the central issues of the controversies that have developed on the validity of risk assessment strategies for TCDD and related compounds. One of the most challenging issues that toxicologists face today is the identification of genes that contribute to or are responsible for increased resistance or sensitivity to TCDD and related compounds. It is assumed that most, if not all, toxic effects of TCDD are mediated more or less through the binding affinity to the Ah receptor. This hypothesis was extended and tries to explain the differences in sensitivity/resistance of animals including humans to TCDD by their total fat (lipid) content. In this respect the gene or genes which is or are responsible for obesity of mammals including humans are of great interest. An obvious linear positive logarithmic relationship between the oral 30-day LD50 (microgram/kg) of TCDD in different species and strains of mammals and their total body fat content (TBF%) was found: log LD50 = 5.30 x log (TBF)-3.22, or LD50 = 0.000603 x (TBF)5.30. By means of this regression the toxicity of TCDD in mammals including humans of different age and/or body weight can be predicted if their total body fat content is known. Examples of single-gene and polygenic disease models in different mammals, such as nonobese diabetic, diabetic, viable yellow, obese, and fat mice, as well as transgenic mice, and other suitable animal models, such as fatty Zucker rats, Han/Wistar (Kuopio) rats, and minipigs, are discussed, and predicted LD50 values of TCDD in these animals and humans are presented.

The mineralization kinetics of the detergent n-dodecylbenzenesulfonate ([14C]LAS) and the plasticizer di(2-ethylhexyl)phthalate ([14C]DEHP) were studied in three fresh sampled soils of different type. Time series of 14CO2 evolution were fitted with various linear and nonlinear models. The kinetics could be represented best by a 3/2-order function with linear adaptation and three parameters: x1 describing the gradient of the exponential part of the curve, x2 the lag phase, and x3 the last, asymptotic part. These parameters as well as the maximal degraded amounts (A) were correlated with various environmental conditions. For LAS, A was similar in all three soils and was positively related to pH in two soils and to humidity in one soil (rendzina). The parameters x1-x3 were positively influenced by soil humidity in all three soils. The degraded amounts A, expressed as percentage of added dose, were independent of initial concentration. Both A and the parameters x1-x3 increased with increasing temperature. Degradation was negligible below 3 degrees C. For DEHP, the degradation was much slower than that of LAS and was most rapid and most complete in the rendzina soil. Relative degradation A was lower for higher initial application rates. Temperature influenced both A and the lag phase. Degradation was not significant below 10 degrees C.

The acute toxicity (48-hr LC50) of lindane (gamma-HCH) to 16 fish species, belonging to eight families, ranges from 22 to 900 micrograms/liter (mean: 150 micrograms/liter). A significant positive linear relationship between the lipid content (% on a wet weight basis) of the fishes and their toxicity to gamma-HCH was found. If the toxicity is referred to 1% lipid, 48-hr LC50 values range between 13.2 and 32 micrograms/liter, and thus the coefficient of variation of the mean is reduced from 139 to 22%. It is concluded that the lipids of aquatic organisms serve as a protective reservoir against the toxic effects of lindane and other lipophilic, relatively persistent organic chemicals, because they are bioconcentrated mainly in the body lipids. Therefore, in organisms with high lipid content, only a relatively small fraction of the hydrophobic chemical can reach target organs (nerves, liver, etc.) and/or receptors. For comparing toxicity data of organic chemicals to aquatic organisms, the total lipid content of the organisms must be considered. The results of this investigation are important in comparative environmental toxicology for risk assessment of freshwater and marine organisms.

The bioconcentration factors of 14C-labeled chlorinated benzenes in plants from soil were quantified in short-term laboratory experiments and correlated to Kow. The correlation was negative for barley and positive for cress. In order to interpret these opposite results, the log/log correlation between partition coefficients and Kow of the chemicals was established also for each step of the uptake, via both roots and leaves. For the first step of root uptake--the partition of the chemicals from soil solids into soil water--the correlation with Kow was negative, whereas it was positive for the second step, the partition roots/soil water, of both plant species. Similarly, the correlation between the first step of foliar uptake--the partition of the chemical from soil into air--and Kow was negative, and that between the second step--the partition between aerial plant parts and air--and Kow was positive for both plant species. The slopes of the regression lines differed between plant species. It may be concluded that Kow can be used as a parameter to predict the uptake of chemicals from soil by plants only if the same class of chemicals and the same plant species is considered.

This paper provides an explanation for a 40-fold difference in the acute toxicity (LC50) of gamma-hexachlorocyclohexane (gamma-HCH, Lindane) in 14 different fish species, based on well recognized principles of toxicokinetics and toxicodynamics in combination with a compilation of data from the literature and some original data. The 48-h median lethal concentration (48-h LC50) of gamma-HCH in 14 fish species, belonging to 6 families, range from 22 to 900 micrograms/l. A significant positive linear relationship was found between lipid content (% of wet weight) and the 48-h LC50 of gamma-HCH in these fish species, revealing that the toxicity of gamma-HCH in various fish species is decreasing with increasing total lipid content. If median lethal concentrations are normalized for 1% lipid content, then the range of 48-h LC50s is reduced to between 18 and 32 micrograms/l. It is concluded that lipids of aquatic organisms can serve (among other functions) as a protective storage site against the toxic effects of gamma-HCH and, possibly, of other lipophilic, persistent organic chemicals which are bioconcentrated in body lipids. Therefore, in organisms with higher lipid content, a smaller fraction of a lipophilic chemical will reach target organs (liver, lung, central and peripheral nerves, etc.) to cause adverse effects. Results suggest that this correlation can be used to extrapolate the acute toxicity (48-h LC50) of gamma-HCH to other fish species if their lipid content is known. Furthermore, the data generated by extrapolation of this correlation could be useful in the environmental risk assessment of freshwater and marine organisms.

Lipophilic chemicals such as chlorinated hydrocarbon insecticides and other persistent chemicals such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) are fat soluble chemicals and are readily bioconcentrated in animal fat depots. The modifying role of the body fat content in the toxicity of chlorinated cyclodiene insecticides to insects and in the toxicity of TCDD to different mammals was investigated. The single oral acute 30-day LD50 data of TCDD in different mammals are presented and correlated with their total body fat content. A two linear regression equation with log/log values was obtained. It is concluded that the storage of TCDD and other related lipophilic and persistent chemicals in lipids of organisms is, in a sense, a detoxication mechanism by which the compounds are removed from sites of action and/or receptors. Therefore, terrestrial organisms such as insects and mammals with higher total body fat content can accumulate and tolerate higher chlorinated hydrocarbon insecticide and TCDD doses than organisms with lower fat content. The different sensitivity of mammals of various species, strains, body weight, sex, age, etc. to acute toxicity of TCDD and related lipophilic persistent chemicals can mainly be explained by differences in total body fat content.

Prediction of the bioconcentration of organic chemicals from water by aquatic organisms has important applications in the management of hazardous chemicals. This study gives a compilation of bioconcentration factors on a wet weight basis (BCFw) of 52 organic chemicals by Daphnia magna from aqueous solution. The bioconcentration factors for the chemicals in Daphnia were successfully correlated with their n-octanol/water partition coefficients (log Kow) using a linear regression analysis. In addition to the ordinary least-square regression technique, the geometric mean regression technique is also used because this takes into account deviations in Kow values. Both results show that the Kow value of a chemical is a good predictor of the BCF in Daphnia. The BCF-Kow relationships between Daphnia, algae (Chlorella), and mussels (Mytilus edulis) are compared with each other.

[phenyl-14C]Monolinuron was applied (2.5 and 1.9 kg/ha) to the soil surface of an outdoor lysimeter in two successive years: then, potatoes were grown. Total recovery of 14C in soil, plants, and leached water was about 55% (of 14C applied) after the first growing period and about 43% after the second growing period. Radioactivity in soil contained 77.1% (based on total 14C recovered in soil) bound residues, 15% monolinuron, and the following conversion products: N-(4-hydroxyphenyl)-N'-methoxy-N'-methylurea, N-(4-chlorophenyl)-N'-methylurea. N-(4-chlorophenyl)methylcarbamate, N-(4-chlorophenyl)-N-methyl-methylcarbamate, and 4-chloroformanilide. The leachate contained 0.8% (based on total 14C recovered in leachate) N-(4-hydroxyphenyl)-N'-methoxy-N'-methylurea. Potato plants contained 0.106 mg/kg radioactive residues in peeled tubers after one growing period and 15.94 mg/kg in the tops; after two growing periods, peeled tubers contained 0.091 mg/kg and tops contained 18.87 mg/kg radioactive residues. These residues consisted of bound 14C (57.9% of total 14C recovered in plants), N-(4-hydroxyphenyl)-N'-methoxy-N'-methylurea, N-(4-chlorophenyl)-N'-methylurea, N-(4-chlorophenyl)methylcarbamate, N-(4-chlorophenyl)-N-methyl-methylcarbamate, and 4,4'-dichlorozobenzene.

Outdoor experiments with [14C]hexachlorobenzene, [14C]pentachlorobenzene, [14C]1,2,4-trichlorobenzene, and [14C]benzene in soil-crop systems indicate that the formation rate of bound residues in soil and plants, expressed as bound residues in percentage of total residue in the sample, decreases with increasing number of chlorine in the molecule and, thus, with increasing chemical stability. The time course of formation and fate of bound residues in soil and plants is characterized by a very slow decrease of residue levels in soil, indicating that biodegradation of bound residues hardly exceeds their reformation from the parent compound during one vegetation period, and by a decrease of residue levels in plants. The portion of bound residues as compared to the total residue increases with time, indicating that bound residues are more persistent than the parent compounds and their soluble metabolites; benzene is an exception. Cress plants, in general, contain less bound residues than do barley plants. Again, benzene is an exception. In deeper soil layers, soil-bound residues occur also. The ratio between bound and extractable residues does not differ to a larger extent between the soil layers.

The uptake of 14C from various 14C-labeled organic chemicals from different chemical classes by barley and cress seedlings from soil was studied for 7 days in a closed aerated laboratory apparatus. Uptake by roots and by leaves via the air was determined separately. Although comparative long-term outdoor studies showed that an equilibrium is not reached within a short time period, plant concentration factors after 7 days could be correlated to some physicochemical and structural substance properties. Barley root concentration factors due to root uptake, expressed as concentration in roots divided by concentration in soil, gave a fairly good negative correlation to adsorption coefficients based on soil organic carbon. Barley root concentration factors, expressed as concentration in roots divided by concentration in soil liquid, gave a positive correlation to the n-octanol/water partition coefficients. Uptake of chemicals by barley leaves via air was strongly positively correlated to volatilization of chemicals from soil. Both root and foliar uptake by barley could be correlated well to the molecular weight of 14 chemicals. Uptake of chemicals by cress differed from that by barley, and correlations to physicochemical substance properties mostly were poor.

[14C]Benzene, [14C]1,2,4-trichlorobenzene, [14C]pentachlorobenzene, and [14C]hexachlorobenzene were applied to soils in outdoor lysimeters to a 10-cm depth (2 mg/kg dry soil); barley and cress plants were grown for one vegetation period and analyzed after varying time intervals. The bioaccumulation factors (concentration of radioactive substances in plants divided by that in soils) of barley were higher than those of cress, except for hexachlorobenzene. In barley, bioaccumulation factors increased with decreasing chlorine content of the molecules, except for benzene, whereas in cress hexachlorobenzene exhibited the highest bioaccumulation factor. The conversion ratios of chlorinated benzenes (percentage of conversion products based on total radioactivity in plants) were negatively correlated to the chlorine content of the molecules and, in barley, positively correlated with time; in general, they were higher in barley than in cress. The concentration of radioactive substances in the plants, as well as bioaccumulation factors, decreased with time, except for a slight increase in benzene-derived residues in barley after 125 days. This effect is due to growth dilution. The percentage of radioactivity in barley seeds, based on that in the whole plant, was negatively correlated to the chlorine content of the molecule.

Three laboratory short-term test systems were used to determine volatilization rates, mineralization rates, and conversion rates of 14 14C-labeled chemicals in soils or soil-plant systems. The chemicals covered a wide range of water solubility, vapor pressure, chemical stability, and biodegradability. In order to compare the data obtained with the environmental behavior of the respective chemicals, data from an outdoor experimental setup which had been shown to give residue data within the range limits of field conditions were used. Volatilization rates, mineralization rates, and conversion rates obtained in the laboratory were correlated to those found under outdoor conditions. Based on these correlations, predictions of field residues were made. The predicted values for total field residues were comparable to those found experimentally with the exception of two chemicals. The prediction of residues of unchanged parent compounds in the field was less satisfactory. The reasons for differences observed are discussed.

A list of environmental chemicals detectable in adipose tissue and/or milk of non-occupationally exposed humans is presented. Besides their physiochemical properties (n-octanol/water partition coefficient and water solubility), their acceptable daily intake (ADI) values, production figures, fate in the environment, concentrations in human adipose tissue, and data from total diet studies from market basket investigations are given. Average bioconcentration factors (BCF) of polychlorinated biphenyls (PCBs), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), DDT, hexachlorobenzene (HCB), dieldrin, hexachlorocyclohexane isomers (alpha-HCH, beta-HCH, gamma-HCH, delta-HCH), pentachlorophenol (PCP), and 3,5-di-tert-butyl-4-hydroxytoluene (BHT) in human adipose tissue are calculated. The bioconcentration factors (wet wt basis) of these compounds are between 3 and 47 times higher in humans than in rats. The environmental chemicals are divided into three groups in respect to their bioconcentration factors in human adipose tissue: group I, high BCF (greater than 100); group II, medium BCF (10-100); and group III, low BCF (less than 10). The bioconcentration factors are useful for hazard assessment of chemicals to humans.

The effects of the test chemicals pentachlorophenol (PCP) and HgCl2 on the bioactivity of microorganisms in three different soils were studied in low and high concentrations (2 and 20 ppm). Bioactivity was measured in long-term experiments (18 weeks) by a threefold application of chemicals to soils of varying moisture content. The selected tests were measurements of ATP, of heat output under aerobic and anaerobic conditions and after amendment with glucose, of soil respiration after the addition of glucose, and Fe(III) reduction. The suitability of each test depends on soil microorganisms, on environmental conditions, and on soil properties. The effects caused by the chemicals were as follows. For the low concentration, stimulation or inhibition were mostly repaired within the observation period. The high concentration mostly induced inhibitions which increased or decreased as a consequence of the repeated application of the chemicals. The effects of chemicals were strongly modified by the soil types: in a soil with high organic matter content, differences to the control were lower than in soils with lower organic matter content. These experiments also indicate that measurement of only one physiological parameter is not sufficient to characterize chemicals ecotoxicologically.

In outdoor lysimeters, [14C]atrazine (0.9 mg/kg dry soil), [14C]atrazine combined with the detergent n-dodecylbenzenesulfonate (0.9 and 10 mg/kg, respectively), [14C]n-dodecylbenzene-sulfonate (10 mg/kg), and [14C]n-dodecylbenzenesulfonate combined with atrazine (10 and 0.9 mg/kg, respectively) were applied to soils. Maize was grown in the first year and barley in the second year. n-Dodecylbenzenesulfonate increased the mobility of atrazine and its metabolites in soil as well as its leaching into water, its uptake by maize plants, and its volatilization from soil. Atrazine had a negative influence on mineralization, mobility in soil, leaching, plant uptake by both species, and binding rates of radiocarbon derived from the surfactant in soil and plants. The results were confirmed by short-term laboratory tests. Whereas the effects of the detergent on the fate of atrazine and its conversion products were apparent only in the first growing season, those of atrazine on the fate of detergent-derived residues could also be observed in the second year due to the persistence of atrazine in soil.

[14C]Aldrin was applied to soils (about 3kg/ha) in outdoor boxes at various locations (Germany, England, and United States), and crops were cultivated (maize, wheat, sugar beets, and potatoes). In the following year, crop rotation experiments were carried out in the same soils without retreatment; in addition, wheat was grown in soils retreated with [14C]aldrin (3.5 kg/ha). After the harvest of both years, the distribution of aldrin and major metabolites (dieldrin; photodieldrin; hydrophilic metabolites including dihydrochlordene dicarboxylic acid; an unidentified nonpolar compound X; and unextractable metabolites) was determined in plants, soils, and leaching water. Two further conversion products, photoaldrin and aldrin-trans-diol, occurred in trace amounts only in a few samples. Metabolic pathways for aldrin under outdoor conditions are presented. The distribution of radioactive residues in soils and plants as well as their quantitative chemical composition are discussed, and comparisons are made between the different experimental sites, the crops, the first and second year, and retreated and nonretreated samples. The quantitative results are compared to those of field trials.