Mutagenic effect of epichlorohydrin. II. Analysis of chromosomal aberrations in lymphocytes of persons occupationally exposed to epichlorohydrin

Estimated daily intake of epichlorohydrin and certain heavy metals of bagged and loose black teas

This study aimed to determine the levels of epichlorohydrin (ECH) and some metals in 3 brands of bagged and loose black teas which are widely marketed in Alexandria markets, Egypt, and estimate the acceptable daily intake as a safety indicator. Gas chromatography-mass spectrometry results revealed that ECH levels significantly differed between the tested brands steeped for 2 min and tea bags contained higher levels than in loose teas and the levels increased by increasing the steep time. These levels of ECH in all the tested brands either in tea bags or loose teas were higher than the guideline value of 0.10 μg/L. Also, the results illustrated that the adding of sucrose or washing of bags with deionized water for 1 min significantly decreased the levels of ECH. In addition, inductively coupled plasma optic emission spectrometry (ICP-OES) results illustrated that the levels of Al, Pb, and Cd were too low in infusions compared to the established guidelines. Because of the high consumption of tea in Alexanria city, Egypt, it is necessary to determine the contribution of tea to the daily dietary intake of ECH, Al, Pb and Cd. In case of the bagged teas, the calculated daily intake of ECH was on average about 55.37 times greater than that in loose teas. The consumption of both bagged and loose teas infusion could not pose a risk for population as the health hazard index was < 1. It can be concluded that consumers who prefer to use tea bags should rinse these bags before preparing the tea brewer, and do not increase the steeping time to more than 2 min.

DNA interstrand cross-linking by epichlorohydrin

Epichlorohydrin (ECH), an important industrial chemical, is a bifunctional alkylating agent with the potential to form DNA cross-links. Occupational exposure to this suspect carcinogen leads to chromosomal aberrations, and ECH has been shown previously to undergo reaction with DNA in vivo and in vitro. We used denaturing polyacrylamide gel electrophoresis to monitor the possible formation of interstrand cross-links within DNA oligomers by ECH and the related compound, epibromohydrin (EBH). Although both compounds did indeed form cross-links between deoxyguanosine residues, EBH was a more efficient cross-linker than ECH. The optimal pH for cross-linking also varied, with ECH more efficient at pH 5.0 and EBH more efficient at pH 7.0. Both agents were relatively flexible in the sequences targeted, with comparable efficiencies for 5'-GGC and 5'GC sites. Furthermore, interstrand cross-linking by the two optical isomers of ECH correlated with their relative cytotoxicities, with R-ECH about twice as potent as S-ECH.

Monitoring of occupational exposure to epichlorohydrin by genetic effects and hemoglobin adducts

The present work is focused on the determination of in vivo doses and studies of genetic effects in workers exposed to epichlorohydrin (ECH). The studied endpoints were hemoglobin (Hb) adducts, frequencies of hprt mutants, micronuclei in cytochalasin B blocked binucleated lymphocytes, sister chromatid exchanges (SCE) and high frequency cells (HFC). Blood samples were collected from office clerks and ECH exposed factory workers at an industrial plant in Germany. The workers were exposed to 0.11-0.23 ppm ECH in the air 45 h per week and to 0.2-2.6 ppm for 3 h per week. Some Swedish non-exposed subjects were also used for Hb adduct measurements. The genetic data, HFC and SCE, showed a significant difference between exposed and unexposed donors. In contrast to earlier studies on SCE, no impact of smoking was observed. Effects on micronuclei were on the borderline of significance, whereas there was no effect for HPRT mutants. The average Hb adduct level was higher in exposed than in non-exposed donors, although the difference was only significant when the exposed group was compared to Swedish controls. Smoking gave significantly increased adduct levels. The absence of significant correlations between individual data for Hb adducts and genetic effects, may be explained by the different periods of time covered by the responses in these endpoints. Whereas Hb adducts reflect the exposure during up to 4 months (i.e. the life span of human erythrocytes), the SCE, and particularly the HFC, seem to accumulate for years in a long-lived fraction of T-lymphocytes without DNA repair. Thus, the adduct data does not reflect the exposure backwards in time unless it can be shown that exposure conditions have remained unchanged. The origin of the background adduct levels in non-smoking control persons is at present not known.

Genetic toxicology of epichlorohydrin: a review

Epichlorohydrin (ECH) is one of the more commercially important aliphatic epoxides used extensively as an industrial intermediate, a laboratory reagent, and as an insecticide. It is a volatile, colourless liquid with an ethereal odour. It behaves as an alkylating agent. Reports have shown it to cause the respiratory and dermal toxicity in animals and humans. It has also been reported to be carcinogenic in experimental models. Thus, the wide-spread use of this aliphatic epoxide is of great concern in human health problem. The purpose of this paper is to critically review and update the mutagenic and clastogenic effects of ECH based on available literature.

Propylene oxide and epichlorohydrin induce DNA strand breaks in human diploid fibroblasts

The induction of DNA strand breaks in human diploid fibroblasts (VH-10) was demonstrated after in vitro exposure with two carcinogenic epoxides, propylene oxide (PO) and epichlorohydrin (ECH). Alkaline DNA unwinding (ADU), pulsed field gel electropharosis (PFGE), and the comet assay were used to measure DNA single. (SSBs) and double-strand breaks (DSBs). A dose-dependent increase of DNA strand breaks, measured by ADU, was observed in the dose range 2.5-20 mMh of PO and 0.25-2 mMh of ECH. The dose-response of ECH was about five times higher compared with that of PO (211 vs. 41 SSBs. 100 Mbp-1.mMh-1). The induction rates of DSBs, measured by PFGE, were found to be 18 times higher for ECH compared to PO (4.8 and 0.27 DSBs.100 Mbp-1.mMh-1 for ECH and PO, respectively). Using these two methods, the SSBs/ DSBs ratio was estimated to be 148 for PO and 44 for ECH. The data obtained by the comet assay also demonstrated a dose-dependent ability of PO and ECH to induce DNA damage. It was found that ECH was about six times more effective as an inducer of DNA strand breaks compared to PO (200 and 32x100 Mbp-1.mMh-1 for ECH and PO, respectively). The SSBs/DSBs ratios calculated using comet assay and PFGE data were 125 for ECH and 41 for PO. In addition, ECH is about 10 times more toxic than PO with respect to survival. These properties of ECH can at least in part be explained by its higher chemical reactivity connected with a higher rate of DNA alkylation.

Reaction of epichlorohydrin with 2'-deoxynucleosides: characterization of adducts

Epichlorohydrin (ECH) is a simple 3-carbon epoxide of industrial importance and thus has the potential for human exposure in the workplace. It has been shown to be genotoxic in several systems and is a compound capable of reacting with biological nucleophiles. This study details the products formed from the reaction of ECH with 2'-deoxynucleosides at pH 7 and 37 degrees C for 6 h. Reaction with 2'-deoxyguanosine yielded 7-(3-chloro-2-hydroxypropyl) guanine (7-CHP-Gua) resulting from alkylation at N-7 of 2'-deoxyguanosine followed by depurination. Two unusual adducts were also partially characterized which resulted from further reaction of 7-CHP-Gua with another molecule of ECH to yield 1,7-bis(3-chloro-2-hydroxypropyl)guanine (1,7-bis-CHP-Gua) which could then cyclize with the exocyclic amino group to yield 1,N2-(2-hydroxypropano)-7-(3-chloro-2-hydroxypropyl) guanine (1,N2-HP-7-CHP-Gua). Reaction with 2'-deoxyadenosine gave only one product, namely 1,N6-(2-hydroxypropano)-2'-deoxyadenosine (1,N6-HP-dAdo). The reaction of 2'-deoxythymidine with ECH also yielded one product which was identified as 3-(3-chloro-2-hydroxypropyl)-2'-deoxythymidine (3-CHP-dThd). A 3-(3-chloro-2-hydroxypropyl)-2'-deoxyuridine (3-CHP-dUrd) product was isolated from the reaction of ECH with 2'-deoxycytidine. This product most likely resulted from the deamination of an initially formed 3-(3-chloro-2-hydroxypropyl) -2'-deoxycytidine (3-CHP-dCyd), a phenomenon which we have previously reported to occur during the reaction of 2'-deoxycytidine with other aliphatic epoxides. Evidence is also presented that 3-CHP-dUrd is converted to 3-(2,3-dihydroxypropyl)-2'deoxyuridine (3-DHP-dUrd) under physiological conditions, with a half-life of 213 h. Reaction of ECH with calf thymus DNA (pH 7.0, 37 degrees C, 3 h) resulted in the formation of 7-CHP-Gua (200 nmol/mg DNA.

Toxicity studies of epichlorohydrin in Sprague-Dawley rats

Adult male and female Sprague-Dawley rats received epichlorohydrin via gavage in distilled water for 10 consecutive days at dose levels of 3, 7, 19, and 46 mg/kg-day, and for 90 days at dose levels of 1, 5, and 25 mg/kg-day. Epichlorohydrin did not adversely effect mortality, but toxicity, at the higher doses, was evident by: 1) losses in body weight gain and organ weights, 2) reductions in food and water consumption, and 3) in the hematological and microscopic examinations in both study periods. Significant decreases in erythrocyte count, hemoglobin, and hematocrit levels were found in the high dose level in males after 10 and 90 days. Dose-related increases in kidney and liver weights were observed in both sexes at 25 mg/kg-day in the 90-day study and in various organs for both 19 and 46 mg/kg-day in the 10-day study. Histopathological examination identified the forestomach as the primary target organ for both sexes and in both studies with significant dose-related increases in mucosal hyperplasia (acanthosis) and hyperkeratosis. Based on the data presented, a lowest observable adverse effect level (LOAEL) for oral exposure of Sprague-Dawley rats to epichlorohydrin is 3 mg/kg-day for 10 days and 1 mg/kg-day is suggested as the no observed adverse effect level (NOAEL) for a 90 day oral exposure. These conclusions were the same whether the lesions were analyzed for each sex individually or whether the data in each study was pooled.

DNA adduct formation by 12 chemicals with populations potentially suitable for molecular epidemiological studies

DNA adduct formation, route of absorption, metabolism and chemistry of 12 hazardous chemicals are reviewed. Methods for adduct detection are also reviewed and approaches to sensitivity and specificity are identified. The selection of these 12 chemicals from the Environmental Protection Agency list of genotoxic chemicals was based on the availability of information and on the availability of populations potentially suitable for molecular epidemiological study. The 12 chemicals include ethylene oxide, styrene, vinyl chloride, epichlorohydrin, propylene oxide, 4,4'-methylenebis-2-chloroaniline, benzidine, benzidine dyes (Direct Blue 6, Direct Black 38 and Direct Brown 95), acrylonitrile and benzyl chloride. While some of these chemicals (styrene and benzyl chloride, possibly Direct Blue 6) give rise to unique DNA adducts, others do not. Potentially confounding factors include mixed exposures in the work place, as well the formation of common DNA adducts. Additional research needs are identified.

Chromosome analysis from peripheral blood lymphocytes of workers after an acute exposure to benzene

A spillage of about 1200 gallons of benzene occurred during the loading of a ship, and 10 workers on a single shift were exposed to benzene. Shortly afterwards, an assay of the urine of these individuals showed that substantial amounts of phenol were being excreted. About three months after the incident samples of venous blood were taken from 10 individuals exposed to benzene and 11 men on a comparable shift who acted as controls. The lymphocytes were stimulated to divide in short term cultures. For each subject, 200 cells at metaphase were examined for chromosome damage using 48 h cultures, and sister chromatid exchanges (SCE) were analysed from about 30 cells in their second division, using 72 h cultures. The most frequent types of aberrations in all the individuals were chromatid gaps, with occasional breaks of chromatids and chromosomes. There were few exchanges within or between the arms of chromatids or chromosomes. More cells in the control than in the exposed group showed damage, an effect that was especially noticeable for chromatid gaps. All values, however, were considered to be within a normal range. There were slightly more SCE in some of the exposed individuals than in the controls and there was a trend towards a positive association between the frequency of SCE recorded for each individual and the maximum value for the excretion of phenol in the urine on the day after the incident. There is no evidence to indicate that benzene induced any type of lasting chromosome damage in the lymphocytes of the 10 exposed workers when cells were examined about three months after the incident.

Mortality in an european cohort occupationally exposed to epichlorohydrin (ECH)

A study was undertaken on the mortality of workers exposed to ECH at four European sites with plants producing epichlorohydrin (ECH), epoxy resins, glycerin, and other specialty chemicals derived from ECH. The vital status of 606 individuals with at least one year of exposure to ECH, starting at least 10 years before the final date of the study on 31 December, 1978, were collected. Mortality was analysed for a subgroup with 10 or fewer years of exposure, and another subgroup with more than 10 years of exposure. Four deaths from different cancers were observed against five expected. No excess mortality from cancer was observed in either subgroup or the complete cohort, which could be related to ECH exposure. The small size of the cohort and the limited number of deaths due to low average age (42 years), as well as the short duration of the observation period, do not allow a firm conclusion to be reached regarding the potential carcinogenicity of ECH in man. Current exposure levels are low, but exposure in the early days of production occasionally reached levels high enough to be irritating. We recommend updating the study 5 years from the final date of the present study, i.e. on 31 December, 1983. Within their limitations this and other epidemiological studies so far provide no evidence for an association between occupational exposure to ECH and the occurrence of malignant neoplasms in man.

Effect of occupational exposure to epichlorohydrin on the frequency of chromosome aberrations in peripheral lymphocytes

The relationship between the level of occupational exposure to epichlorohydrin (ECHH) and the clastogenic effect was studied on a group of 33 workers. The effect of ECHH was assessed by differences in the frequency of chromosome aberrations in peripheral blood lymphocytes in ECHH-exposed and control groups. In the group exposed to the average ECHH concentration, 0.384 mg X m-3, during the last 6 months, the cytogenetic analysis revealed 2.00 +/- 0.23% AC (aberrant cells) (0.0203 B/C, breaks per cell) as compared with 1.68 +/- 0.23% AC (0.0172 B/C) in the matching controls. These results indicate that an average concentration lower than 0.40 mg X m-3 ECHH in the working atmosphere has no significant clastogenic effect on human peripheral lymphocytes.

Evaluation of epichlorohydrin (ECH) genotoxicity. Microsomal epoxide hydrolase-dependent deactivation of ECH mutagenicity in Schizosaccharomyces pombe in vitro

The mutagenic effect of epichlorohydrin (ECH) on the yeast Schizosaccharomyces pombe was studied in vitro in the presence of mouse-liver S9 mix and microsomal and cytosolic fractions. The incubations were always performed in the absence of NADPH-generating systems. S9 mix and microsomes from phenobarbital-pretreated mice significantly reduced ECH mutagenicity, whereas the cytosol did not result in any deactivating effect. The various protein contents of the subcellular fractions were not involved in any scavenger effect as regards ECH mutagenic activity. Moreover, the addition of reduced glutathione to the incubation mixtures indicated that it did not play an important role, either per se or through the enzyme(s) glutathione-S-epoxide transferase(s), in preventing ECH genotoxicity. Our results suggest that microsomal epoxide hydrolase(s) represents the major step in the detoxifying pathway of ECH. These observations were supported by measurements of the specific epoxide hydrolase activity in the various fractions on the same substrate.

Teratogenic evaluation of epichlorohydrin in the mouse and rat and glycidol in the mouse

Pregnant outbred albino rats (CD) and mice (CD-1) were given epichlorohydrin by gastric intubation on d 6-15 of gestation. The rats were killed on d 21 (d 18 for mice) and the offspring checked for gross, visceral, and skeletal malformations. Epichlorohydrin caused a significant reduction in the weight gain of pregnant rats at 80 mg/kg.d as compared with the control group treated only with the vehicle. However, there was no evidence of teratogenicity in the rat fetuses even at a dose level (160 mg/kg.d) that caused the death of some of the treated dams. Epichlorohydrin also did not produce a statistically significant increase in the average percent of malformed mouse fetuses, even at 160 mg/kg.d, a dose that killed 3 of 32 treated dams. The 120 and 160 mg/kg.d levels did cause a significant (p less than 0.05) reduction in the average fetal weight as compared with controls. In addition, the 120 mg/kg.d dose produced the statistically significantly increase in the liver weight of the pregnant mouse. These observations indicate that the 120 and 160 mg/kg.d dose levels were toxic toward the dams and their unborn offspring. In a similar mouse study, glycidol showed no evidence of teratogenicity. There was a significant increase in the number of stunted fetuses at 200 mg/kg.d, but all of these were present in a single litter. Further, the same dose killed 5 of 30 dams.

Biologic monitoring of exposure to chemical mutagens in the occupational environment

Occupational exposure to chemical mutagens can be monitored by measuring the chemical interaction that occurs between the exposing agent and biologic macro-molecules. Such interaction is detectable in the body fluids as adducts of, e.g., DNA or glutathione. The mutagenic compounds or their metabolites can also be measured from urine samples, by use of bacterial mutagenicity assays. Much basic research is still needed before these methodologies are applicable for routine monitoring. At present, cytogenetic approaches appear to be nearest to routine surveillance in detecting early biologic effects in exposed humans. Studies on structural chromosome aberrations or sister chromatid exchanges (SCEs) in peripheral blood lymphocytes obviously detect different molecular injuries, and the results from in vivo occupational exposures do not necessarily correlate. Somatic chromosome damage should always be considered a warning sign of potentially adverse effects, and such damage should lead to decreased exposure to the causative agent.

Mammalian in vivo and in vitro cytogenetic assays: a report of the U.S. EPA's gene-tox program

This report presents an assessment made by the U.S. Environmental Protection Agency Gene-Tox Program's Work Group on mammalian cytogenetics of the clastogenic effects of chemicals in in vivo and in vitro mammalian cell assays. This assessment is based on information provided by the Environmental Mutagen Information Center, Oak Ridge National Laboratory, with the proviso that the experimental protocol used in these papers was adjudged to be acceptable by standards outlined by the Work Group. Some data were accepted as "qualitative only" because the protocol used was fairly close to that proposed as suitable. Using these criteria, 177 papers were selected for review. 6 assays were reviewed: bone marrow (32 papers, 31 chemicals), spermatogonial (10 papers, 10 chemicals), spermatocyte (25 papers, 25 chemicals), oocyte or early embryo (18 papers, 19 chemicals), in vitro cell culture (30 papers, 66 chemicals), and leukocyte (66 papers, 53 chemicals). Each assay was considered separately, and comparisons were then made between them for their similarities or differences in producing a positive or negative clastogenic effect of a particular chemical or chemical class. A large proportion of the available cytogenetic data was not suitable for inclusion in the final data base because of poor experimental design or unsatisfactory reporting of the information. It was not possible to recommend any one assay for determining potential clastogenicity because each had its own particular advantages and limitations and provided unique information. For demonstrating in vivo effects, the bone-marrow assay is probably the simplest and most economical. If only in vitro exposures were considered, leukocytes or cultured mammalian cell lines would be suitable. However, there are advantages to using leukocytes because they are a synchronous population, at least through their cell division, and because of the ready availability of human cells. In general, there was good agreement between clastogenicity and carcinogenicity.

The mutagenic action of aliphatic epoxides

The mutagenic action of 45 epoxides was investigates in Luria and Delbrück's fluctuation test with Klebsiella pneumoniae as test organism. In this test, 36 of the 45 epoxides appeared to be mutagenic. The mutagenicity of 1,2-epoxides decreased with increasing length of the carbon chain. The mutagenic activity of compounds with a non-terminal epoxide group appeared to be less than that of substances with a terminal one. Generally 1,2-epoxide compounds with electronegative groups were more mutagenic than 1,2-epoxypropane. Of the diepoxides, 1,2,3,4-diepoxybutane appeared to be more mutagenic than 1,2,7,8-diepoxyoctane, while the ring compounds 1,2,5,6-diepoxycyclooctane was hardly mutagenic. The ring compound 4-vinylcyclohexenedioxide, used in electron microscopy that the antibiotic fosfomycin is among the more potent mutagenic substances investigated in this study.

Potential carcinogenic and mutagenic industrial chemicals. I. Alkylating agents

A variety of alkylating agents, acylating agents, peroxides, halogenated derivatives, and nitrogen derivatives have been reviewed, principally in terms of their synthesis, areas of utility, stability, distribution, reactivity, levels of exposure, population at risk, metabolism, carcinogenicity, and mutagenicity.

Cytogenetic analysis of peripheral lymphocytes in workers occupationally exposed to epichlorohydrin

Peripheral lymphocytes of 3 groups of adult subject (28 workers occupationally exposed for 4 years to epichlorohydrin [ECHH], 34 matching controls and 21 subjects of the general population (control group) were cytogenetically analysed. In total, 11 806 metaphases were scored. The following frequencies of aberrant cells (bearing mostly chromatid and chromosome breaks) were detected in individual groups: ECHH-exposed group 3.12%; matching controls 2.06%; general population control group 1.33%. The results seem to indicate that even the concentration of 1 mg ECHH/m3 was capable of increasing the frequency of aberrant cells in the occupationally exposed group of workers.

Monitoring the occupational exposure to mutagens by the cytogenetic analysis of human peripheral lymphocytes in vivo

Cytogenetic analysis of peripheral lymphocytes of workers occupationally exposed to mutagens appears to be a routinely acceptable technique to recommend as a biological indicator of genetic damage to somatic cells due to an overexposure to chemicals in the workplace. A scheme is suggested of genetic risk estimates in workers on the background of cytogenetically detected levels of aberrant cells.

Mutagenicity of halogenated and oxygenated three-carbon compounds

Four structurally related three-carbon compounds, known for their antifertility activity in the male, and the brominated derivatives of two of these compounds were tested for mutagenic activity by the Salmonella typhimurium test of Ames et al. In the presence of strain TA-100, a base-pair substituion detector strain, 1,2-dibromo-3-chloropropane (DBCP), was the most active compound tested but required enzymatic conversion by 59 microsomal preparation to an active mutagen. Three of these compounds containing an epoxide group-epichlorohydrin, epibromohydrin, and glycidol-were highly active direct mutagens, not requiring 59 for activation, alpha-Chlorohydrin was the least active compound tested; alpha-bromohydrin was 40 times more active than its chlorinated analog. Epibromohydrin was only slightly more active than epichlorohydrin, but both were highly active. With both of the halogenated epoxides, 59 preparation caused a substantial decrease in mutagenic activity at every concentration tested. All six compounds showed dose-related responsiveness for the base-pair substitution detector strains used. However, they were relatively inactive against the frameshift detector strain of S. typhimurium, TA-98. Glycerol, propylene glycol, and n-propanol, which are also three-carbon compounds containing one or more hydroxy groups, were inactive when trested at high concentrations with strain TA-100.

A study of the mutagenicity of anesthetics and their metabolites

The commonly used volatile anesthetics, several of their metabolites, and drugs frequently employed by the anesthesiologist were screened for mutagenicity in the Salmonella/rat-liver microsomal assay system developed by Dr. B. Ames and his colleagues. Chloral hydrate, both a sedative and metabolite of trichloroethylene, was found to be weakly mutagenic. Other compounds testing including halothane, isoflurane, methoxyflurane, diazepam and chlordiazepoxide were not mutagenic. Non-volatile compounds were tested for their ability to inhibit growth of bacterial strains with decreased capacity to repair damaged DNA. None of the compounds tested inhibited the growth of DNA-repair-deficient strains relative to a strain with normal DNA-repair. Halothane and trilene were tested for direct interaction with DNA; under the experimental conditions employed, no direct interaction of these compounds and DNA could be detected.