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Haloacetic acids (HAAs) are ubiquitous in drinking water and have been associated with impaired male reproductive health. However, epidemiological evidence exploring the associations between HAA exposure and reproductive hormones among males is scarce. In the current study, the urinary concentrations of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), the internal exposure markers of HAAs, as well as sex hormones (testosterone [T], progesterone [P], and estradiol [E 2 ]) were measured among 449 Chinese men. Moreover, in vitro experiments, designed to simulate the real-world scenarios of human exposure, were conducted to assess testosterone synthesis in the Leydig cell line MLTC-1 and testosterone metabolism in the hepatic cell line HepG2 in response to low-dose HAA exposure. The DCAA and TCAA urinary concentrations were found to be positively associated with urinary T, P, and E 2 levels (all p < 0.001), but negatively associated with the ratio of urinary T to E 2 (p < 0.05). Combined with in vitro experiments, the results suggest that environmentally-relevant doses of HAA stimulate sex hormone synthesis and steroidogenesis pathway gene expression in MLTC-1 cells. In addition, the inhibition of the key gene CYP3A4 involved in the testosterone phase Ⅰ catabolism, and induction of the gene UGT2B15 involved in testosterone phase Ⅱ glucuronide conjugation metabolism along with the ATP-binding cassette (ABC) transport genes (ABCC4 and ABCG2) in HepG2 cells could play a role in elevation of urinary hormone excretion upon low-dose exposure to HAAs. Our novel findings highlight that exposure to HAAs at environmentally-relevant concentrations is associated with increased synthesis and excretion of sex hormones in males, which potentially provides an alternative approach involving urinary hormones for the noninvasive evaluation of male reproductive health following exposure to DBPs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) are two typical non-volatile disinfection by-products (DBPs) found in drinking water. Increasing evidence has demonstrated that they show reproductive toxicity. However, whether they might have endocrine disrupting properties remains largely unknown. To discover this, we treated male mice or pregnant mice with 0, 1-, 10 2 -, 10 3 -, 10 4 -, or 5 × 10 4 -fold maximal concentration level (MCL) of DCAA or TCAA in drinking water. In male mice, the levels of testosterone in serum and androgen receptor (AR) in testis were declined with ≥ 10 3 -fold MCL of DCAA (26.4 mg/kg/d) or TCAA (52.7 mg/kg/d). In pregnant mice, miscarriage rates were increased with ≥ 10 4 -fold MCL of DCAA (264 mg/kg/d) or ≥ 10 3 -fold MCL of TCAA. The levels of FSH in serum were increased and those of estradiol and progesterone were reduced with ≥ 10 3 -fold MCL of DCAA or TCAA. The protein levels of estrogen receptors (ERα and ERβ) in ovary were reduced with ≥ 10 2 -fold MCL of DCAA (2.64 mg/kg/d) or TCAA (5.27 mg/kg/d). Exposure to some certain fold MCL of DCAA or TCAA also altered the protein levels of ERα and ERβ in uterus and placenta. Exposure to 5 × 10 4 -fold MCL of both DCAA and TCAA showed the combined effects. Therefore, both DCAA and TCAA could be considered as novel reproductive endocrine disrupting chemicals, which might be helpful for further assessment of the toxicological effects of DCAA and TCAA and the awareness of reproductive endocrine disrupting properties caused by DCAA and TCAA in drinking water., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Background: Disinfection byproducts (DBPs) as ovarian toxicants have been documented in toxicological studies. However, no human studies have explored the effects of exposure to DBPs on diminished ovarian reserve (DOR)., Objective: To assess whether urinary biomarkers of exposure to drinking-water DBPs were associated with DOR risk., Methods: A total of 311 women undergoing assisted reproductive technology were diagnosed with DOR in the Tongji Reproductive and Environmental (TREE) cohort from December 2018 to August 2021. The cases were matched to the controls with normal ovarian reserve function by age in a ratio of 1:1. Urinary trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA) were quantified as biomarkers of drinking-water DBP exposures. The conditional logistic regression and restricted cubic spline (RCS) were used to explore urinary biomarkers of drinking-water DBP exposures in associations with the risk of DOR., Results: Elevated urinary DCAA levels were associated with higher DOR risk [adjusted odds ratio (OR) = 1.87; 95 % confidence interval (CI): 1.16, 3.03 for the highest vs. lowest quartiles; P for trend = 0.016]. The association was confirmed in the RCS model, with a linear dose-response curve (P for overall association = 0.029 and P for non-linear association = 0.708). The subgroup analysis by age and body mass index (BMI) showed that urinary DCAA in association with DOR risk was observed among women ≥35 years old and leaner women (BMI < 24 kg/m 2 ), but the group differences were not statistically significant. Moreover, a U-shaped dose-response curve between urinary TCAA and DOR risk was estimated in the RCS model (P for overall association = 0.011 and P for non-linear association = 0.004)., Conclusions: Exposure to drinking-water DBPs may contribute to the risk of DOR among women undergoing assisted reproductive technology., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Standardised tests are often used to determine the ecotoxicity of chemicals and focus mainly on one or a few generic endpoints (e.g. mortality, growth), but information on the sub-cellular processes leading to these effects remain usually partial or missing. Flow cytometry (FCM) can be a practical tool to study the physiological responses of individual cells (such as microalgae) exposed to a stress via the use of fluorochromes and their morphology and natural autofluorescence. This work aimed to assess the effects of five chlorine-based disinfection by-products (DBPs) taken individually on growth and sub-cellular endpoints of the green microalgae Raphidocelis subcapitata. These five DBPs, characteristic of a chlorinated effluent, are the following monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), bromochloroacetic acid (BCAA) and 1,1-dichloropropan-2-one (1,1-DCP). Results showed that 1,1-DCP had the strongest effect on growth inhibition (EC 50 = 1.8 mg.L -1 ), followed by MCAA, TCAA, BCAA and DCAA (EC 50 of 10.1, 15.7, 27.3 and 64.5 mg.L -1 respectively). Neutral lipid content, reactive oxygen species (ROS) formation, red autofluorescence, green autofluorescence, size and intracellular complexity were significantly affected by the exposure to the five DBPs. Only mitochondrial membrane potential did not show any variation. Important cellular damages (>10%) were observed for only two of the chemicals (BCAA and 1,1-DCP) and were probably due to ROS formation. The most sensitive and informative sub-lethal parameter studied was metabolic activity (esterase activity), for which three types of response were observed. Combining all this information, an adverse outcome pathways framework was proposed to explain the effect of the targeted chemicals on R. subcapitata. Based on these results, both FCM sub-cellular analysis and conventional endpoint of algal toxicity were found to be complementary approaches., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Harmful algal (cyanobacterial) blooms (HABs) are increasing throughout the world. HABs can be a direct source of toxins in freshwater sources, and associated algal organic matter (AOM) can act as precursors for the formation of disinfection by-products (DBPs) in drinking water. This study investigated the impacts of algae on DBP formation using treatment with chloramine, which has become a popular disinfectant in the U.S. and in several other countries because it can significantly lower the levels of regulated DBPs formed. Controlled laboratory chloraminations were conducted using live field-collected algal biomass dominated by either Phormidium sp. or Microseira wollei (formerly known as Lyngbya wollei) collected from Lake Wateree and Lake Marion, SC. Sixty-six priority, unregulated or regulated DBPs were quantified using gas chromatography (GC)-mass spectrometry (MS). The presence of HAB-dominated microbial communities in source waters led to significant increases in more toxic nitrogen-containing DBPs (1.5-5 fold) relative to lake waters collected in HAB-free waters. Compared to chlorinated Phormidium-impacted waters, chloraminated waters yielded lower total DBP levels (up to 123 μg/L vs. 586 μg/L for low Br - /I - waters), but produced a greater number of brominated, iodinated, and mixed halogenated DBPs in high Br - /I - waters. Among the DBPs formed in Phormidium-impacted chloraminated waters, dichloroacetic acid, trichloromethane, chloroacetic acid, chloropropanone, and dichloroacetamide were dominant. For Microseira wollei-impacted chloraminated waters, total DBP concentrations ranged from 33 to 145 μg/L (approximately 3-5 times lower than chlorination), with dichloroacetic acid, dichloroacetamide, and trichloromethane dominant. Overall, chloramination significantly reduced calculated cytotoxicity and genotoxicity in low Br - and I - waters, but produced 1.3 fold higher calculated cytotoxicity (compared to chlorine) with high Br - /I - waters due to increased formation of more toxic iodo- and mixed halogenated DBPs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Significant health risks are caused by trace levels of haloacetic acids (HAAs) in drinking water. We used graphene oxide (GO), a high-performance absorbent, to remove monochloroacetic acid (MCAA), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA). 31.6%, 27.1% and 30.2% of MCAA, DCAA and TCAA in drinking water could be rapidly removed within 2 min by the interaction of intermolecular hydrogen bonds between GO and HAAs. On the other hand, as a type of weak interaction, intermolecular hydrogen bonds are easy to fracture, which leads to the recovery of GO. The removal efficiency of MCAA, DCAA and TCAA monotonously decreased with increasing pH from 3 to 11. Temperature was not an important influence on the removal efficiency of HAAs, and only affected the interaction of intermolecular hydrogen bonds between GO and HAAs. A continuous adsorption process was used for further improving the removal efficiency of HAAs, and the concentration of total HAAs decreased from 436 to 52.5 μg L -1 after five adsorption processes. The total contact time was just 2.25 min, which was faster than other reported adsorbents, and total HAAs could be decreased by 88%. The innovative process in this study provides an effective method for application of GO to rapidly remove HAAs in drinking water.

It is crucial to explore the source, formation process and interdependence of disinfection byproducts (DBPs) to reduce their risk on public health. In this investigation, a source water was chlorinated to evaluate the initial formation rates and the maximum yields of trichloromethane (TCM), dichloroacetic acid (DCAA), and trichloroacetic acid (TCAA) based on a hyperbola model. The results showed that TCM achieved the highest initial formation rate and maximum theoretical concentration compared with DCAA and TCAA. The TCM yield can be used to forecast the yields of DCAA and TCAA throughout the whole reaction process, and the yields of chloral hydrate (CH), dichloroacetonitrile (DCAN) and 1,1,1-trichloropropanone (1,1,1-TCP) within the initial reaction stage. Besides, the raw water, settled water and filtered water collected from a drinking water treatment plant were divided into five fractions, respectively, by ultrafiltration membranes to evaluate their DBP formation after chlorination. Compared with the medium molecular weight species, high and low molecular weight organic matters exhibited relatively high specific regulated and unregulated DBP yields (expressed as μg/mg C), respectively. Humic acid-like compositions predominantly contributed to regulated DBP yields, while soluble microbial by-product-like compounds preferentially generated DCAN. The correlation study revealed that the TCM could also serve as an indicator for the measured DBPs from chlorination of sample fractions with different molecular weight. Finally, it was found that the theoretical cytotoxicity was enhanced during chlorination of filtered water compared with chlorination of settled water., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

People are exposed to chlorinated by-products (CBPs) through the consumption of cold tap water (CTW) (ingestion, inhalation, dermal contact) but also through the use of hot tap water (HTW) in such activities as showering and bathing (inhalation, dermal contact). This study focuses on the impact of residential water heating on CBP levels in tap water. Trihalomethane (THM) and haloacetic acid (HAA) levels were measured in the CTW and HTW of 50 residences located in two distribution systems supplied by chlorinated surface water during summer and winter. Results show important differences between CBP levels measured in cold and hot tap water. However, the magnitude of changes differs according to the specific species of THMs and HAAs, the season, the distribution system and the location within the same distribution system. Residential water heating led to an increase in average THM levels for the two distribution systems studied, which tended to be greater in winter. Residential water heating affected the two main HAA species found in the area studied (dichloroacetic (DCAA) and trichloroacetic (TCAA) acids) differently. In fact, the average DCAA levels increased due to water residential heating while a small change in average levels was observed for TCAA. However, the water heating impact on HAAs (in terms of importance and sometimes of tendency (increase vs. decrease)) may also differed between residences. The influence of seasons on the change in the average DCAA and TCAA levels (in μg/L) from residential water heating was not statistically significant except for TCAA levels in one distribution system. Results show the importance of considering site-specific characteristics of CTW (CBP level, temperature, residual chlorine, etc.) to estimate the levels of CBPs in HTW in CBP exposure assessment studies (and not to generalize for an entire population). The reported data can thus be useful in assessing for exposure to DBPs in epidemiological studies., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Dichloroacetate (DCA) is a promising safe anticancer drug that cured a patient with chemoresistant non-Hodgkin's lymphoma and treated lactic acidosis effectively. The well-known mechanism of DCA action is through stimulating Krebs cycle (stimulating pyruvate dehydrogenase via inhibiting pyruvate dehydrogenase kinase). This prevents lactate formation (Warburg effect) depriving cancer cells of lactate-based benefits e.g. angiogenesis, chemoresistance and radioresistance. Here, we introduce novel evidence-based hypotheses to explain DCA-induced anticancer effects. On pharmacological and biochemical bases, we hypothesize that DCA is a structural antagonist of acetate competing with it for target enzymes and biological reactions. We hypothesize that DCA exerts its anticancer effects via depriving cancer of acetate benefits. We hypothesize also that acetate is an antidote of DCA capable of treating DCA toxicity. Many reports support our hypotheses. Acetate is vital for cancer cells (tumors depend on acetate) and DCA is structurally similar to acetate. DCA exerts opposite effects to acetate. Acetate caused a decrease in serum potassium, phosphorus and glucose, and an increase in serum lactate, citrate, free fatty acids and ketone bodies (serum acetoacetate and beta-hydroxybutyrate levels). Acetate decreased the proportion of active (dephosphorylated) pyruvate dehydrogenase in perfused rat heart. DCA produced quite opposite effects. Intravenous infusion of acetate produced metabolic alkalemia while DCA caused minimal effects on acid-base status. Acetate is important for cancer cells metabolism and survival as elevated acetate can drive resistance to targeted cancer treatments. Acetate is required for epidermal growth factor receptor vIII mutation in lethal brain tumors. Experimentally, DCA inhibited acetate oxidation in hearts of normal rats and reversed inhibitory effects of acetate on the oxidation of glucose. During presence of DCA with no glucose in heart perfusions with [1-14C]acetate, DCA decreased the specific radioactivity of acetyl CoA and its product citrate. This proves our hypotheses that DCA is an antimetabolite that antagonizes acetate for vital reactions in cancer cells. Acetate may be used as an antidote to combat DCA toxicity., (Copyright © 2018. Published by Elsevier Ltd.)

Objective: The aim of this study was to examine associations between craniofacial birth defects (CFDs) and disinfection by-product (DBP) exposures, including the sum of four trihalomethanes (THM4) and five haloacetic acids (HAA5) (ie, DBP9)., Methods: We calculated first trimester adjusted odds ratios (aORs) for different DBPs in a matched case-control study of 366 CFD cases in Massachusetts towns with complete 1999 to 2004 THM and HAA data., Results: We detected elevated aORs for cleft palate with DBP9 (highest quintile aOR = 3.52; 95% CI: 1.07, 11.60), HAA5, trichloroacetic acid (TCAA), and dichloroacetic acid. We detected elevated aORs for eye defects with TCAA and chloroform., Conclusion: This is the first epidemiological study of DBPs to examine eye and ear defects, as well as HAAs and CFDs. The associations for cleft palate and eye defects highlight the importance of examining specific defects and DBPs beyond THM4.

Water disinfection plays a crucial role in water safety but it is also a matter of concern as the use of disinfectants promotes the formation of disinfection by-products (DBPs). Haloacetic acids (HAAs) are one of the major classes of DBPs since they are frequently found in treated water, are ubiquitous, pervasive and have high water solubility, so a great concern emerged about their formation, occurrence and toxicity. Exposure to HAAs is influenced by consumption patterns and diet of individuals thus their bioavailability is an important parameter to the overall toxicity. In the current study the bioacessibility of the most representative HAAs (chloroacetic acid - MCAA, bromoacetic acid - MBAA, dichloroacetic acid - DCAA, dibromoacetic acid - DBAA, and trichloroacetic acid - TCAA) after simulated in vitro digestion (SIVD) in tap water and transport across Caco-2 monolayers was evaluated. Compounds were monitored in 8 points throughout the digestion phases by an optimized LC-MS/MS methodology. MCAA and MBAA were not bioaccessible after SIVD whereas DCAA, DBAA and TCAA are highly bioaccessible (85 ± 4%, 97 ± 4% and 106 ± 7% respectively). Concerning transport assays, DCAA and DBAA were highly permeable throughout the Caco-2 monolayer (apparent permeability and calculated fraction absorbed of 13.62 × 10(-6) cm/s and 90% for DCAA; and 8.82 × 10(-6) cm/s and 84% for DBAA), whereas TCAA showed no relevant permeability. The present results may contribute to efficient risk analysis studies concerning HAAs oral exposure from tap water taking into account the different biological behaviour of these chemically similar substances., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Cheese can contain regulated disinfection by-products (DBPs), mainly through contact with brine solutions prepared in disinfected water or sanitisers used to clean all contact surfaces, such as processing equipment and tanks. This study has focused on the possible presence of up to 10 trihalomethanes (THMs) and 13 haloacetic acids (HAAs) in a wide range of European cheeses. The study shows that 2 THMs, (in particular trichloromethane) and 3 HAAs (in particular dichloroacetic acid) can be found at μg/kg levels in the 56 cheeses analysed. Of the two types of DBPs, HAAs were generally present at higher concentrations, due to their hydrophilic and non-volatile nature. Despite their different nature (THMs are lipophilic), both of them have an affinity for fatty cheeses, increasing their concentrations as the percentage of water decreased because the DBPs were concentrated in the aqueous phase of the cheeses., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

A biologically activate carbon (BAC) filter was continuously operated on site for the treatment of haloacetic acids (HAAs) in an outdoor swimming pool at an average empty bed contact time (EBCT) of 5.8 min. Results showed that BAC filtration was a viable technology for direct removal of HAAs from the pool water with a nominal efficiency of 57.7% by the filter while the chlorine residuals were 1.71 ± 0.90 mg/L during the study. THMs and TOC were not removed and thus were not considered as indicators of the effectiveness of BAC filtration. Increased EBCT in the range of 4.5 and 6.4 min led to improved HAA removal performance, which could be best fit by a logarithmic regression model. BAC filtration also affected the HAA speciation by removing more dichloroacetic acid (DCAA) than trichloroacetic acid (TCAA), resulting in a lower ratio of DCAA/TCAA in the filtered effluent. However, the observation of an overall constant ratio could be attributable to a complex formation and degradation mechanism occurring in swimming pools., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Water used in a food factory is frequently disinfected with chlorine, which originates disinfection by-products: haloacetic acids (HAAs) make up the second most prevalent class of these products. In this paper we propose the first static HS-GC-MS method developed for direct HAA determination in beverages; the method has higher sensitivity, simplicity and reliability than the only alternative available in the literature. From 150 beverages analysed, it is possible to conclude that at least 2 HAAs (dichloro- and trichloroacetic acids, DCAA and TCAA) are always present in beverages prepared with treated water, which remains constant for 2 or 3 months in the beverages. Moreover, beverages of 100% fruit juices and soft drinks prepared with mineral water (free of HAAs) do not contain any HAA at significant values. Therefore, DCAA and TCAA may indicate of the presence of treated water in beverages., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Dissolved organic matter (DOM) represents the major pool of organic precursors for harmful disinfection byproducts, such as haloacetic acids (HAAs), formed during drinking water chlorination, but much of it remains molecularly uncharacterized. Knowledge of model precursors is thus a prerequisite for understanding the more complex whole water DOM. The utility of HAA formation potential data from model DOM precursors, however, is limited due to the lack of comparability to water samples. In this study, the formation kinetics of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), the two predominant HAA species, were delineated upon chlorination of seventeen model DOM precursors and sixty-eight inland lake water samples collected from the Upper Midwest region of the United States. Of particular interest was the finding that the DCAA and TCAA formation rate constants could be grouped into four statistically distinct clusters reflecting the core structural features of model DOM precursors (i.e., non-β-diketone aliphatics, β-diketone aliphatics, non-β-diketone phenolics, and β-diketone phenolics). A comparative approach built upon hierarchical cluster analysis was developed to gain further insight into the chlorine reactivity patterns of HAA precursors in inland lake waters as defined by the relative proximity to four model precursor clusters. This work highlights the potential for implementing an integrated kinetic-clustering approach to constrain the chlorine reactivity of DOM in source waters.

In this study, we propose a simple strategy based on flow injection and field-amplified sample-stacking CE-ESI-MS/MS to analyze haloacetic acids (HAAs) in tap water. Tap water was passed through a desalination cartridge before field-amplified sample-stacking CE-ESI-MS/MS analysis to reduce sample salinity. With this treatment, the signals of the HAAs increased 300- to 1400-fold. The LODs for tap water analysis were in the range of 10 to 100 ng/L, except for the LOD of monochloroacetic acid (1 μg/L in selected-ion monitoring mode detection). The proposed method is fast, convenient, and sensitive enough to perform on-line analysis of five HAAs in the tap water of Taipei City. Four HAAs, including trichloroacetic acid, dichloroacetic acid, dibromoacetic acid, and monobromoacetic acid, were detected at concentrations of approximately 1.74, 1.15, 0.16, and 0.15 ppb, respectively., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This paper demonstrates that disinfection byproducts (DBP) concentration profiles in heated water were quite different from the DBP concentrations in the cold tap water. Chloroform concentrations in the heated water remained constant or even decreased slightly with increasing distribution system water age. The amount of dichloroacetic acid (DCAA) was much higher in the heated water than in the cold water; however, the maximum levels in heated water with different distribution system water ages did not differ substantially. The levels of trichloroacetic acid (TCAA) in the heated water were similar to the TCAA levels in the tap water, and a slight reduction was observed after the tap water was heated for 24 h. Regardless of water age, significant reductions of nonregulated DBPs were observed after the tap water was heated for 24 h. For tap water with lower water ages, there were significant increases in dichloroacetonitrile (DCAN), chloropicrin (CP), and 1,1-dichloropropane (1,1-DCP) after a short period of heating. Heating of the tap water with low pH led to a more significant increase of chloroform and a more significant short-term increase of DCAN. High pH accelerated the loss of the nonregulated DBPs in the heated water. The results indicated that as the chlorine doses increased, levels of chloroform and DCAA in the heated water increased significantly. However, for TCAA, the thermally induced increase in concentration was only notable for the chlorinated water with very high chlorine dose. Finally, heating may lead to higher DBP concentrations in chlorinated water with lower distribution system temperatures.

Chlorine has been utilized in the early stages of water treatment processes as disinfectant. Disinfection for drinking water reduces the risk of pathogenic infection but may pose a chemical threat to human health due to disinfection residues and their by-products (DBP) when the organic and inorganic precursors are present in water. In the last two decades, many modeling attempts have been made to predict the occurrence of DBP in drinking water. Models have been developed based on data generated in laboratory-scale and field-scale investigations. The objective of this paper is to develop a predictive model for DBP formation in the Alexandria governorate located at the northern west of Egypt based on field-scale investigations as well as laboratory-controlled experimentations. The present study showed that the correlation coefficient between trihalomethanes (THM) predicted and THM measured was R (2)=0.88 and the minimum deviation percentage between THM predicted and THM measured was 0.8 %, the maximum deviation percentage was 89.3 %, and the average deviation was 17.8 %, while the correlation coefficient between dichloroacetic acid (DCAA) predicted and DCAA measured was R (2)=0.98 and the minimum deviation percentage between DCAA predicted and DCAA measured was 1.3 %, the maximum deviation percentage was 47.2 %, and the average deviation was 16.6 %. In addition, the correlation coefficient between trichloroacetic acid (TCAA) predicted and TCAA measured was R (2)=0.98 and the minimum deviation percentage between TCAA predicted and TCAA measured was 4.9 %, the maximum deviation percentage was 43.0 %, and the average deviation was 16.0 %.

Disinfection byproducts were measured in the finished drinking water from ten water treatment plants in three Chinese cities - Guangzhou, Foshan and Zhuhai. A total of 155 water samples were collected in 2011 and 2012. The median (range) of trihalomethane (THM) and haloacetic acid (HAA) levels were 17.7 (0.7-62.7) μg/L and 8.6 (0.3-81.3) μg/L, respectively. Chloroform, dichloroacetic acid and trichloroacetic acid were the dominant species observed in Guangzhou and Foshan water, while brominated THMs predominated in water from Zhuhai. Haloacetonitriles, haloketones, chloral hydrate and trichloronitromethane were usually detected at levels ranging from unquantifiable (<0.2μg/L) to 12.2μg/L (choral hydrate). THMs and HAAs showed clear seasonal variations with the total concentrations higher in winter than in summer. Correlations among DBP levels varied, with the strongest linear correlation observed between chloroform and chloral hydrate levels (R(2)=0.77). The risk of cancer from ingestion, inhalation and dermal contact exposure to THMs was estimated. CHCl2Br contributed the highest percentage of the cancer risk from ingestion pathway and CHCl3 contributed the highest of cancer risk from inhalation pathway., (Copyright © 2013 Elsevier B.V. All rights reserved.)

An innovative haloacetic acid (HAA) removal process was developed. The process consisted of a zero-valent iron (Fe(0)) column followed by a biologically active carbon (BAC) column that were efficient in degrading tri- and di-HAAs, and mono- and di-HAAs, respectively. The merit of the process was demonstrated by its performance in removing trichloroacetic acid (TCAA). An empty bed contact time of 10 min achieved nearly complete removal of 1.2 μM TCAA and its subsequent products, dichloroacetic acid (DCAA) and monochloroacetic acid (MCAA). HAA removal was a result of chemical dehalogenation and biodegradation rather than physical adsorption. Preliminary kinetic analyses were conducted and the pseudo-first-order rate constants were estimated at ambient conditions for Fe(0) reduction of TCAA and biodegradation of DCAA and MCAA by BAC. This innovative process is highly promising in removing HAAs from drinking water, swimming pool water, and domestic or industrial wastewater., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Twelve typical nitrogenous organic compounds including herbicides, pesticides, amino acids, industrial products etc in polluted raw water were selected to investigate formation of typical carbonaceous and nitrogenous DBPs during chlorination and chloramination. To indentify the formation mechanism of carbonaceous and nitrogenous disinfection byproducts from nitrogenous chemicals, chlorination and chloroamination of urea herbicides, triazine herbicides, amino acid, and other compounds were investigated. As a result, the potential precursors for different DBPs were defined as well. It has been identified that widely used urea herbicides could produce as many as 9 specific DBPs. The chlorotoluron shows highest reactivity and yields chloroform (CF), monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), 1,1-dichloro-acetone (1,1-DCP), 1,1,1-trichloro-acetone (1,1,1-TCP), chloropicrin (NTCM), dichloro-acetonitrile (DCAN), dimethylnitrosamine (NDMA). The results indicated that aldicarb and dinoseb are important precursors of CF, DCAA, MCAA, NTCM as well. High concentrations of CF and DCAA were found during L-tryptophan chlorination. Furthermore, DBPs formation pathways and mechanisms were suggested during chlorination and chloramination of chlorotoluron, ametryn, dinoseb L-tryptophan.

Chloroacetic acids, formed during the disinfection process in potable water production, are considered to pose a potential risk to human health. This article deals with dichloroacetic acid (DCAA) removal from drinking water by using a process of bentonite based adsorptive ozonation. This process is formed by combined addition of ozone, bentonite and Fe(3+). During the reaction, DCAA is removed by the joint effect of adsorption, ozonation and catalytic oxidation. In addition, under the effect of the adsorption, natural organic matters (NOM) can be adsorbed onto the bentonite surface, resulting in a reduced scavenging effect toward HO· radicals, and hence eliminate the negative effect of NOM on DCAA removal. At the initial stage of the reaction, Fe(3+) is rapidly hydrolyzed to polycations and adsorbed onto the bentonite surface or into its structural layers. This positively charges the surface of the bentonite and increases its surface area, resulting in a strong adsorption of HA or DCAA. Furthermore, Fe(3+) catalyzes ozone decomposition to form HO· thus further improving the efficiency. The adsorptive ozonation has been shown to be potentially advantageous in destruction of toxic, dissolved pollutants in drinking water, and appears to have great potential for a wide range of treatment applications.

Eight typical drinking water supplies in China were selected in this study. Both source and tap water were used to investigate the occurrence of chlorinated disinfection byproducts (DBPs), and seasonal variation in the concentrations of trihalomethanes (THMs) of seven water sources was compared. The results showed that the pollution level for source water in China, as shown by DBP formation potential, was low. The most encountered DBPs were chloroform, dichloroacetic acid, trichloroacetic acid, and chlorodibromoacetic acid. The concentration of every THMs and haloacetic acid (HAA) compound was under the limit of standards for drinking water quality. The highest total THMs concentrations were detected in spring.

The effects of the crystalline structure and surface functional groups of porous inorganic materials on the adsorption of dichloroacetic acid (DCAA) were evaluated by using hexagonal mesoporous silicates (HMS), two surface functional group (3-aminopropyltriethoxy- and 3-mercaptopropyl-) modified HMSs, faujasite Y zeolite and activated alumina as adsorbents, and compared with powdered activated carbon (PAC). Selective adsorption of HAA(5) group was studied by comparing single and multiple-solute solution, including effect of common electrolytes in tap water. Adsorption capacities were significantly affected by the crystalline structure. Hydrogen bonding is suggested to be the most important attractive force. Decreasing the pH lower than the pH(zpc) increased the DCAA adsorption capacities of these adsorbents due to electrostatic interaction and hydrogen bonding caused by protonation of the hydronium ion. Adsorption capacities of HAA(5) on HMS did not relate to molecular structure of HAA(5). Common electrolytes did not affect the adsorption capacities and selectivity of HMS for HAA5, while they affected those of PAC.

Haloacetic acids (HAAs) are a class of byproducts resulting from the reaction of chlorinated disinfectants with natural organic matter. These chemicals have been found in animal studies to possibly influence hepatic, reproductive, and developmental functions, and they may be mutagenic and carcinogenic. Because HAAs are hydrophilic and strongly acidic, it is a challenge to measure them at low levels. In this study, nine traditional HAAs and monoiodoacetic acid, an emerging disinfection byproduct, are analyzed in water directly. HAAs were separated on a BetaMax Acid column or a HILIC UPLC column, and they were detected by negative electrospray ionization-tandem mass spectrometry. Although the on-column limits of detection of HAAs were lower when using an HILIC UPLC column (0.08-2.73 microg/L) than when using a BetaMax Acid column (0.18 to 71.5 microg/L), to use an HILIC UPLC column, it was required to dissolve water samples in 90% acetonitrile before injection and result in sample dilution. BetaMax Acid column was found to be more suitable for the analysis of HAAs in drinking water because there was no need of sample preparation. Major species of HAAs, such as dichloroacetic acid and trichloroacetic acid, and other primary species (e.g., dibromoacetic acid, bromochloroacetic acid and bromodichloroacetic acid) can be detected using the BetaMax Acid column at concentrations higher than 1-3 microg/L.

The combined solid phase extraction (SPE)-ion chromatography (IC) method was developed for the analysis of trace haloacetic acids (HAAs) in drinking water. The tested HAAs included monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), monobromoacetic acid (MBAA) and dibromoacetic acid (DBAA). For trace determination of HAAs in real drinking water samples, conditions of LiChrolut EN SPE cartridge were investigated for HAAs preconcentration and matrix elimination. Elution was carried out by 2 mL of sodium hydroxide (10 mmol/L) with the flow rate of 2 mL/min. The Dionex IonPac AS16 column (250 mm x 4 mm i. d.), a high capacity and hydroxide-selective anion-exchange column designed for the determination of polarizable anions, was chosen for chromatographic separation. HAAs were analyzed with a concentration gradient of NaOH with the flow rate of 0.8 mL/min and detected by suppressed conductivity. A 500 microL sample loop was used. The detection limits of this SPE-IC method for MCAA, DCAA, DBAA and TCAA were 0.38-1.69 microg/L and MBAA was 12.5 microg/L under 25-fold preconcentration. The results demonstrate that the method is suitable for the analysis of trace haloacetic acids in drinking water.

Haloacetic acids (HAAs) are a family of compounds whose environmental concentrations have been extensively studied, primarily in Europe. Depending on the compound, their sources are believed to be both natural and anthropogenic. To better understand possible sources and contribute to the knowledge of the global distribution of these compounds, especially between the Northern and Southern Hemispheres, samples of precipitation, soils, and conifer needles were collected from Canada, Malawi, Chile, and the U.K. Precipitation samples exhibited highest HAA concentrations in collections from Canada, and lowest in those from Malawi. Malawi samples contained measurable levels of monobromoacetic acid (MBA) (56 ng/ L) unlike those from most other locations (< 9 ng/L). Soil HAA concentration levels were highest in the U.K. (e.g., 7.3 ng/g average TCA) and lowest in Malawi (0.8 ng/g average TCA), with Chile having higher levels (4.8 ng/g average TCA) than Canada (3 ng/g average TCA). Malawi soils contained small amounts of MBA (2 ng/g), in common with the two most southern of the 11 Chilean sites. Analysis of soil cores (10-cm depth sliced at 1 cm) from sites in Malawi and Chile showed that trichloroacetic acid (TCA) generally declined with depth while mono- and dichloroacetic acid (MCA and DCA) showed no trend. MCA, DCA, and TCA concentrations in archived U.K. soil samples increased by factors of 2, 4, and 5-fold over 75 years while TFA showed no consistent trend. Monochloroacetic acid (MCA) was detected in pine needles collected from Malawi. U.K. needle samples had the highest concentrations of all chloroacetic acids (CAAs): MCA, 2-18 ng/g; dichloroacetic acid (DCA), 2-38 ng/g; and trichloroacetic acid (TCA), 28-190 ng/g. Conifer needles from Canada and Chile contained CAAs at levels ranging from < 2 to 16 ng/g wet wt. Trifluoroacetic acid concentrations generally declined with increasing elevation in the samples from the Rocky Mountains in western Canada. The results indicate that concentrations of HAAs are greatest in the industrialized Northern Hemisphere but there are significant amounts of these compounds in the less industrialized Southern Hemisphere.

Trichloroethylene (TCE) and some of its metabolites are potentially carcinogenic compounds that the general population is commonly exposed to in drinking water. Concentrations of TCE, dichloroacetic acid (DCA) and trichloroacetic acid (TCA) given to laboratory animals in cancer bioassays are high, whereas drinking water levels of the compounds are very low. It is not clear whether the trace amounts of TCE, DCA and TCA in drinking water pose a cancer risk to humans. The accuracy of pharmacokinetic studies relies on the analytical method from which blood and tissue concentration data are obtained. Models that extrapolate cancer risks of TCE and its metabolites from laboratory animals to humans, in turn, rely on the results of pharmacokinetic studies. Therefore, it is essential to have reliable analytical methods for the analysis of TCE and its metabolites. This paper reviews the methods currently in the literature for the analysis of TCE, DCA, TCA and, to a lesser extent, chloral hydrate (CH). Additional aspects of analytical methods such as method validation, species preservation and future directions in the analysis of TCE and its metabolites are also discussed., (Copyright (c) 2005 John Wiley & Sons, Ltd.)

A simple and rapid headspace method for gas chromatographic determination of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) in drinking water was developed. Acidic methanol esterification followed by a headspace technique using a capillary column gas chromatograph (GC) equipped with an electron capture detector (ECD) was applied to determine the levels of DCAA and TCAA in drinking water. The major advantages of this method are the use of acidic methanol as the derivatization agent instead of the hazardous diazomethane, and esterification is carried out in water instead of organic solvent. DCAA and TCAA methyl esters produced in the reaction were determined directly by a headspace GC/ECD method. The linear correlation coefficients at concentrations ranging from 0 to 60 microg/L were 0.992 and 0.996 for DCAA and TCAA, respectively. The relative standard deviations (RSD, %) for the determination of DCAA and TCAA in drinking water were 15 and 21.3%, respectively (n=3). The detection limits of this method were 3 and 0.5 microg/L for DCAA and TCAA, respectively, and the recovery was 68-103.2% for DCAA and TCAA.

Adsorption performance of 5 GACs were compared on two abundant haloacetic acids (HAAs) as disinfection by-products (dichloroacetic acid and trichloroacetic acid). The adsorption behaviours of the two HAAs were well correlated with Langmuir equation. When the two HAAs co-existed, trichloroacetic acid tended to be adsorbed more easily. The adsorption capacity of a foreign GAC-A for dichloroacetic acid was 4.4-5.7 times that of domestic GACs, and 3.8 times that of another foreign GAC-B, while the adsorption capacity of a foreign GAC-A for trichloroacetic acid was 4.0-5.4 times that of domestic GACs, and 2.6 times that of another foreign GAC-B. The equilibrium study of competitive adsorption between dichloroacetic acid and trichloroacetic acid on GAC-A demonstrates that the relative adsorption capacity of HAAs has a linear increase with their relative equilibrium concentration. The adsorption capacity for trichloroacetic acid is sensitive to changes at its equilibrium concentration greater than that for dichloroacetic acid.

A new and simple approach is described for the determination of the haloacetic acids (such as mono-, di- and trichloroacetic acids) usually found in drinking water as chlorination by-products after disinfection processes and acetic acid. The new approach, termed vacancy ion-exclusion chromatography, is based on an ion-exclusion mechanism but using the sample solution as the mobile phase, pure water as the injected sample, and a weakly acidic cation-exchange resin column (TSKgel OApak-A) as the stationary phase. The addition of sulfuric acid to the mobile phase results in highly sensitive conductivity detection with sharp and well-shaped peaks, leading to excellent and efficient separations. The elution order was sulfuric acid, dichloroacetic acid, monochloroacetic acid, trichloroacetic acid, and acetic acid. The separation of these acids depends on their pKa values. Acids with lower pKa values were eluted earlier than those with higher pKa, except for trichloroacetic acid due to a hydrophobic-adsorption effect occurring as a side-effect of vacancy ion-exclusion chromatography. The detection limits of these acids in the present study with conductivity detection were 3.4 microM for monochloroacetic acid, 0.86 microM for dichloroacetic acid and 0.15 microM for trichloroacetic acid.

An extraction technique using MTBE (methyl tert. butyl ether) and reagent water in combination with ion chromatography and conductivity determination was developed to quantify dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) concentrations in raw water after chlorination. The detection limit of the method was 0.45 and 1.50 microg/L for DCAA and TCAA, respectively. Mean values of recovery ranged from 90 to 96% for DCAA and 95 to 108% for TCAA. The evaluation of recovery and precision of the method indicates that the performance characteristics are comparable with gas chromatographic (GC) methods reported in literature. In addition, the procedure is simple, fast, and does not need any derivatization step. Application of the analytical method to the determination of DCAA and TCAA in real samples is shown.

Headspace solid-phase microextraction (SPME) was studied as a possible alternative to liquid-liquid extraction for the analysis of haloacetic acids (HAAs) in water. The method involves derivatization of the acids to their ethyl esters using sulphuric acid and ethanol after evaporation, followed by headspace SPME with a polydimethylsiloxane fibre and gas chromatography-ion trap mass spectrometry (GC-IT-MS). The derivatization procedure was optimized: maximum sensitivity was obtained with esterification for 10 min at 50 degrees C in 30 microl of sulphuric acid and 40 microl of ethanol. The headspace SPME conditions were also optimized and good sensitivity was obtained at a sampling temperature of 25 degrees C, an absorption time of 10 min, the addition of 0.1 g of anhydrous sodium sulfate and a desorption time of 2 min. Good precision (RSD lower than 10%) and detection limits in the ng l(-1) range (from 10 to 200 ng l(-1)) were obtained for all the compounds. The optimized procedure was applied to the analysis of HAAs in tap water and the results obtained by standard addition agreed with those of EPA method 552.2, whereas discrepancies due to matrix interferences were observed using external calibration. Consequently, headspace SPME-GC-IT-MS with standard addition is recommended for the analysis of these compounds in drinking water.

Dichloroacetic acid (DCA) is a contaminant found in treated drinking water due to chlorination. DCA has been shown to be a complete hepatocarcinogen in both mice and rats. In this study we developed a rapid and sensitive high-performance liquid chromatography (HPLC) method to simultaneously detect DCA and its metabolites, oxalic acid, glyoxylic acid and glycolic acid in blood and urine samples of animals sub-chronically administered with DCA (2 g/l) in drinking water. Both urine and plasma samples were treated minimally before HPLC analysis. Separation and detection of DCA and its metabolites were achieved using an anion-exchange column and a conductivity detector. The mobile phase consisted of an initial concentration of 0.01 mM sodium hydroxide in 40% methanol followed by a linear gradient from 0.01 mM to 60 mM sodium hydroxide in 40% methanol for 30 min. The lower detection limit for DCA and each of its three major metabolites was 0.05 microg/ml. DCA and its metabolites gave a linear response range from 0.05 to 100 microg/ml. Plasma DCA was also analyzed by gas chromatography (GC), and the results obtained correlated with those from the HPLC method (correlation coefficient=0.999). While available HPLC techniques offer sensitive procedures to detect either glycolic acid or oxalic acid, the described HPLC method has the unique advantage of determining simultaneously the parent compound (DCA) and its three major metabolites (oxalic acid, glyoxylic acid and glycolic acid) in biological samples, without complex sample preparation.

This study compares four different commercial sorbents, LC-SAX (a quaternary ammonium anion exchanger), LiChrolut EN (a highly crosslinked styrene-divinylbenzene), Envi-Carb (a graphitized carbon black) and Oasis HLB [a macroporous poly(divinylbenzene-co-N-vinylpyrrolidone) copolymer], for the solid-phase extraction (SPE) of various haloacetic compounds from aqueous samples. The recoveries with the different sorbents were studied by coupling an off-line SPE system to capillary electrophoresis with indirect photometric detection. The recoveries were highest when LiChrolut EN was used. The limits of detection for the compounds are in the low microgram per litre range and the recovery values are over 80% for dichloroacetic acid and trichloroacetic acid, two of the most habitual haloacetic acids in chlorinated water, when 500 ml of standard solution was preconcentrated using this sorbent. Finally, the performance of the method with different water samples, the effect of chlorination in a treatment plant and the evolution of the haloacetic acids in the water distribution system were tested and the results were compared with those obtained using liquid-liquid extraction and gas chromatography-mass spectrometry.

Trichloroacetic acid (TCA) and dichloroacetic acid (DCA) are environmental contaminants that are suspected human carcinogens. To obtain more detail on the role of the liver in the kinetics of TCA and DCA, experimental studies in the isolated perfused rat liver (IPRL) system were conducted. The IPRL system was dosed with either 5 or 50 micromol of either TCA or DCA (25 or 250 microM initial concentration, respectively). TCA and DCA concentrations were followed in perfusion medium and bile for 2 h. The chemical concentration in liver was determined at the end of exposure. Liver viability was monitored by measuring leakage of lactate dehydrogenase (LDH) into perfusion medium and the rate of bile production. Studies performed with TCA showed that the total TCA concentration in perfusion medium decreased slightly during the first 30 min of exposure and remained constant thereafter. Most TCA, greater than 90% of total, was bound to albumin in the perfusion medium. A low, linear excretion rate of TCA in bile was obtained. The calculated free TCA concentration in the liver intracellular water space was higher than the unbound TCA concentration in the perfusion medium. Parallel studies with DCA showed that the DCA concentration in perfusion medium decreased rapidly. Of the total DCA in the perfusion medium, 60% was bound to albumin. The concentration of DCA in bile decreased over time. There was no DCA detectable in the liver after 2 h of exposure at both DCA concentrations. Enzyme leakage and bile production did not change in the presence of TCA or DCA, indicating that these concentrations were not acutely cytotoxic to the liver., (Copyright 1998 Academic Press.)

A capillary zone electrophoresis (CZE) system for determining haloacetic acids in water was optimized with indirect photometric detection. Two different carrier electrolytes, potassium hydrogenphthalate and sodium 2,6-naphthalenedicarboxylate, were evaluated in terms of sensitivity and two different electroosmotic flow modifiers, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide, were tested. Parameters such as electrolyte concentration and pH, and the concentration of the electroosmotic flow modifiers, which affect the CZE separations, were investigated. The method was used to determine haloacetic acids in chlorine tap water using the liquid-liquid extraction process.

In this work, substrate selection was monitored in the left ventricle of the canine myocardium by following pyruvate and lactate oxidation under in vivo conditions at basal and elevated workloads. These studies were conducted in the open chest model using dynamic 13C NMR techniques in the presence and absence of dichloroacetic acid (DCA), a well-known activator of pyruvate dehydrogenase (PDH). Following the infusion of (3-(13)C) pyruvate or (3-(13)C) lactate into the left anterior descending artery, highly variable 13C enrichments of glutamate, alanine, aspartate, and citrate were noted under low (RPP < 14,500 mmHg/min), intermediate (RPP = 15,000-25,000 mmHg/min), and high (RPP > 25,500 mmHg/min) rate pressure products (RPP). At low workloads, the myocardium typically oxidized the infused (3-(13)C) pyruvate or (3-(13)C) lactate and incorporated the labeled carbon into the glutamate pool as expected. However, in a few notable instances (n = 3), 13C-enriched pyruvate and lactate were unable to label the glutamate pool under in vivo conditions even at the lowest RPPs, indicating a lack of selection for these substrates by the tricarboxylic acid (TCA) cycle. Nonetheless, the levels of glutamate C4 enrichment observed at low workloads could usually be enhanced by infusion of DCA. Importantly, 13C NMR extract analysis revealed that (3-(13)C) pyruvate or (3-(13)C) lactate labeling of the glutamate pool was reduced (< 20%) at high workloads in spite of increased DCA concentrations.

The chlorinated acetic acids, in particular dichloroacetic acid (DCA), are found as chlorine disinfection by-products in finished drinking water supplies. DCA has previously been demonstrated to be a mouse liver carcinogen. Chronic studies are described in which male Fischer (F344) rats were exposed to DCA in their drinking water. In the first study, 28 day old rats were exposed to a regimen of 0.05, 0.5 and 5.0 g/l DCA. When animals in the high dose group began to exhibit peripheral hind leg neuropathy, the dose was lowered in stages to 1 g/l. These animals were sacrificed at 60 weeks due to the severe, irreversible neuropathy and were not included in this analysis. The remaining groups of animals were treated for 100 weeks. In the second study, rats were initially exposed to 2.5 g/l DCA which was lowered to 1 g/l after 18 weeks. The mean daily concentration (MDC) of 1.6 g/l was calculated over the 103 week exposure period. Time-weighted mean daily doses (MDD) based on measured water consumption were 3.6, 40.2 and 139 mg/kg bw/day for the 0.05, 0.5 and 1.6 g/l DCA respectively. Based upon the pathologic examination, DCA induced observable signs of toxicity in the nervous system, liver and myocardium. However, treatment related neoplastic lesions were observed only in the liver. A statistically significant increase of carcinogenicity (hepatocellular carcinoma) was noted at 1.6 g/l DCA. Exposure to 0.5 g/l DCA increased-hepatocellular neoplasia, (carcinoma and adenoma) at 100 weeks. These data demonstrate that DCA is an hepatocarcinogen to the male F344 rat. Calculation of the MDD at which 50% of the animals exhibited liver neoplasia indicated that the F344 male rat (approximately 10 mg/kg bw/day) is ten times more sensitive than the B6C3F1 male mouse (approximately 100 mg/kg bw/day). A "no observed effects level' (NOEL) of 0.05 g/l (3.6 mg/kg/day) was the same as for the mouse (3-8 mg/kg/day).

Metabolism of trichloroethylene (TRI) and its major metabolite, trichloroacetic acid (TCA), by gut content and gut microflora cultures was studied to gain an insight into the role of enterohepatic circulation in TRI metabolism. TRI and TCA were incubated anaerobically with rat and mouse cecal contents and TCA was additionally incubated anaerobically and aerobically with microflora cultures from mice. Although TRI was not metabolized by rat or mouse cecal contents. TCA was metabolized to dichloroacetic acid (DCA) by cecal contents. DCA formation in microflora cultures was dependent on initial TCA concentration, duration of incubation, and initial bacterial number. DCA was not observed in aerobic cultures exposed to TCA. These results suggest that strict anaerobic microorganisms of the gut may partly be responsible for dechlorination of TCA to DCA.

18 different swimming pool waters in the Bonn-Rhein-Sieg area were analysed for trihalogenmethanes, halogenated acetic acids, 2,2-dichloropropionic acid, dihalogenacetonitriles and chloral hydrate. Most substances mentioned above were determined in almost every sample reaching total concentrations up to 538 micrograms/l. Considering the results one can see that some of the main pollutants are polar organic compounds like di- and trichloroacetic acid as well as chloral hydrate.

Chloramphenicol produced by cultures of Streptomyces species 3022a supplemented with sodium [1,2-13C]acetate was labelled with 13C exclusively in the dichloromethine (2.6 +/- 0.1%) and carbonyl (0.59 +/- 0.05% carbon atoms. Satellite signals from 13C-13C coupling between covalently bonded 13C-enriched carbon atoms were too intense to be attributed to random combination of labelled atoms at the average enrichments measured, but their intensity relative to those of the signals for uncoupled 13C atoms indicated that most of the precursor had been incorporated after 13C-13C bond fission. Since [2,3-13c]succinic acid enriched only the carbonyl carbon atom of chloramphenicol, these results suggest that neither acetate nor a Krebs cycle intermediate is a direct precursor of the dichloroacetyl group. Cultures supplemented with [2-3h]-or [2h2]-dichloroacetic acid incorporated negligible amounts of isotope into the antibiotic; on this evidence, the free acid is not an intermediate in chloramphenicol biosynthesis and the acylation step may precede chlorination.