A survey of EPA/OPP and open literature data on selected pesticide chemicals tested for mutagenicity. I. Introduction and first ten chemicals

Ecotoxicity of malathion pesticide and its genotoxic effects over the biomarker comet assay in Daphnia magna

Malathion is a highly toxic organophosphate insecticide, being one of the most widely used in the world and is generally used for insect control in food production. Thus, ecotoxicological studies have been used to verify its toxic effects on aquatic organisms, such as Daphnia magna and biomarkers, as the comet assay. The comet assay is a microgel electrophoresis method for the detection and quantification of DNA strand breaks in individual cells. Cells were obtained from Daphnia magna after disaggregation of newborn organisms, exposed at concentrations of 0.23 μg L^-1 and 0.47 μg L^-1 for 48 h. Malathion has shown to cause damage to DNA of the exposed organisms. It was also observed the need of further studies to standardize the comet assay technique for Daphnia magna, once methodologies used present several differences.

Genomic damage induced by the widely used fungicide chlorothalonil in peripheral human lymphocytes

Chlorothalonil is an important broad spectrum fungicide widely used in agriculture, silviculture, and urban settings. As a result of its massive use, chlorothalonil was found in all environmental matrices, with consequent risks to the health of terrestrial and aquatic organisms, as well as for humans. We analyzed the effects of chlorothalonil on human lymphocytes using in vitro chromosomal aberrations (CAs) and micronuclei (MNi) assays. Lymphocytes were exposed to five concentrations of chlorothalonil: 0.600 µg/mL, 0.060 µg/mL, 0.030 µg/mL, 0.020 µg/mL, and 0.015 µg/mL, where 0.020 and 0.600 µg/mL represent the ADI and the ARfD concentration values, respectively, established by FAO/WHO for this compound; 0.030 and 0.060 μg/mL represent intermediate values of these concentrations and 0.015 μg/mL represents the ADI value established by the Canadian health and welfare agency. We observed cytogenetic effects of chlorothalonil on cultured human lymphocytes in terms of increased CAs and MNi frequencies at all tested concentrations, including the FAO/WHO ADI and ARfD values of 0.020 and 0.600 μg/mL, respectively, but with exception of the Canadian ADI value of 0.015 μg/mL. Finally, no sexes differences were found in the levels of CAs and MNi induced by different chlorothalonil concentrations. Similarly, the mitotic index and the cytokinesis-block proliferation index did not show any significant effect on the proliferative capacity of the cells, although at the chlorothalonil concentration of 0.600 μg/mL the P-values of both indices were borderline.

The research of genetic toxicity of β-phellandrene

β-Phellandrene, a plant extract, can be used as natural pesticides and synthetic materials. As a factor that human may be exposed to, the toxicity information about β-phellandrene is scared at present. This study focused on the genetic toxicity of β-phellandrene. The genetic toxicity of β-phellandrene was evaluated by micronucleus test, comet assay, Ames test, and chromosomal aberration test. In this study, 2850, 1425, 712.5mg/kg β-phellandrene were used in vivo experiments (comet assay and micronucleus test). For Ames test, pure β-phellandrene and different concentrations were used in the experiment. According to the results of cell viability assay (MTT test), the concentration of chromosomal aberration test was formulated. The result of comet assay showed that β-phellandrene can significantly induce DNA damage at the dosage of 1425 and 2850mg/kg. While the results of Micronucleus test and chromosome aberration test showed that β-phellandrene does not lead to apparently genetic toxicity on chromosome level. Ames tests suggest that β-phellandrene had the ability to increase gene mutation with or without S9 mixture. So, it could be drawn that β-phellandrene would have certain genetic toxicity, and the toxicity is reflected as DNA strand breaks and mutation. This study filled the lack of genetic toxicity study of β-phellandrene, and enriched information for risk assessment for β-phellandrene.

Influence of author's affiliation and funding sources on the results of cohort studies on occupational cancer

BACKGROUND

Reliability and credibility of research conducted by industry have been questioned, including in the field of occupational health.

METHODS

Cohort studies on occupational cancer published between 2000 and 2010 were compared according to their results, their conclusions, their funding, and the affiliation of their authors.

RESULTS

Overall, 510 articles were included. Studies published by authors with public affiliation or funded by public grants concluded that their study showed an excess of cancer more frequently (P = 0.01) than studies published by authors with private affiliation or funded by private grants (88% [95%CI = 85-91] vs. 73% [95%CI = 56-88] and 92% [95%CI = 86-97] vs. 71% [95%CI = 57-84], respectively). Discrepancies between statistical results and conclusion occurred more frequently in articles written by authors from the private sector than from the public sector (42% [IC95% = 26-60] vs. 23% [IC95% = 18-26], P = 0.02).

CONCLUSIONS

Industry affiliations of authors or industry support of studies are associated with the results of published studies on occupational cancer. The underlying mechanisms warrant further investigation.

Soil genotoxicity induced by successive applications of chlorothalonil under greenhouse conditions

Greenhouse production of vegetables has been developed rapidly in China. High temperature and humidity inside the greenhouse make this environment more suitable for fast reproduction of fungal diseases. Fungicides are among the chemicals used extensively in the greenhouse to prevent crops from invasive infections by phytopathogens; however, little is known about the accumulation of fungicides in soil and their effect on soil quality under greenhouse conditions. In the present study, the accumulation of the fungicide chlorothalonil (CT) and its toxic metabolite hydroxy-chlorothalonil (HCT) in soil as well as their related soil genotoxicity under greenhouse conditions was investigated. The results indicated that both CT and HCT accumulated in soil with repeated applications of CT, and the accumulation level was strongly correlated to application dosage and its frequency. In addition, soil genotoxicity, which was measured by Vicia faba, also increased with the accumulation of CT and HCT, and the main contributor to this phenomenon was CT rather than HCT. The data demonstrated that successive applications of fungicides may result in their accumulation in soil and thus a decline in soil quality.

Exposure to lambda-cyhalothrin, a synthetic pyrethroid, increases reactive oxygen species production and induces genotoxicity in rat peripheral blood

Lambda-cyhalothrin (LTC) is a synthetic pyrethroid with a broad spectrum of insecticidal and acaricidal activities used to control a wide range of insect pests in a variety of applications. However, there is little known about its adverse effects, in particular those related to its genotoxicity in humans. To elucidate the genotoxicity mechanisms of LTC, the micronuclei (MN) frequencies, the levels of reactive oxygen species (ROS), erythrocyte osmotic fragility, nitrite (NO) formation, protein carbonyl (PCO) levels and malondialdehyde (MDA) production were evaluated for a period of 7, 14 and 21 days. Our results show that exposure rat to LTC (1/10DL50 = 6.23 mg/kg) for a period of 7, 14 and 21 days induced a noticeable genotoxic effect in rat peripheral blood evidenced by a significant increase in the frequency of MN only at day 21 of treatment. Significant differences between the two groups were observed in erythrocyte osmotic fragility. Further, a significant (p < 0.01) increase in ROS contents, NO formation, PCO levels and lipid peroxidation in erythrocytes were observed at different times of treatments, suggesting the implication of oxidative stress in its toxicity. These results confirm the genotoxic and the pro-oxidant effects of LTC in rat peripheral blood.

Assessing the genotoxic potential of chlorothalonil drift from potato fields in Prince Edward Island, Canada

Chlorothalonil, a broad-spectrum nonsystemic foliar fungicide, is one of the most extensively used pesticide active ingredients on Prince Edward Island, Canada, for blight control on potatoes. In ambient air-sampling programs conducted in 1998 and 1999 and from 2002 to 2004, chlorothalonil was measured in 97% of air samples collected. It is known to produce severe eye and skin irritation, is cytogenic and is considered a possible human carcinogen by the United States Environmental Protection Agency and the International Agency for Research on Cancer. Inhalation studies that quantify chlorothalonil subchronic effects (e.g., genotoxicity) are lacking. The purpose of this study was to assess the possible genotoxic potential of chlorothalonil under field conditions by using the alkaline comet assay to assess DNA damage in CD-1 mice. Mice were selected as a surrogate species for wild small mammals (e.g., meadow voles, deer mice) known to inhabit areas adjacent to potato fields. Mice were placed at three locations downwind of a chlorothalonil application (0, 30, and 100 m) and at one up-wind control location at least 30 m from the field. Downwind mice were exposed to drift throughout the spray period (approximately 30 min) and for an additional hour after spraying. Air samples were collected during the spray trials (before, during, and after spraying) using high-volume polyurethane foam and PM(2.5) air samplers. Pesticide deposits were measured using 20 × 25 cm glass-fibre filters. After exposure, blood was collected from each mouse, and DNA strand breaks in white blood cells measured using comet assay. Results suggest that metrics of DNA damage [tail length (TL), percent DNA in tail] were not significantly related to total air chlorothalonil concentration from the three spray trials (r (2) = 0.000, P = 0.907 for TL; r (2) = 0.001, P = 0.874 for percent DNA). In addition, no significant difference in DNA damage was observed between exposed (at 0 m) and control animals (P = 0.357 for TL; P = 0.958 for percent DNA). Based on these results it can be concluded that wild small mammals living beside fields sprayed with chlorothalonil are at no greater risk of exposure-related DNA damage than conspecifics from unexposed areas.

Transplacental genotoxicity evaluation of cypermethrin using alkaline comet assay

Transplacental genotoxic effect of cypermethrin technical was investigated. Three doses (25, 50 and 75 mg/kg body weight) were administered to groups of pregnant Wistar rats during 6-15 days of gestation. Animals were killed on gestation day 20. Fetal blood and liver samples were evaluated for DNA damage using alkaline comet assay. A marginal increase in the mean percentage of DNA damage was recorded in both blood and liver samples of fetuses from cypermethrin-treated dams, but the values were not statistically significant. No skeletal or visceral fetal abnormalities were recorded in treated groups. Nevertheless, the results lead to an understanding that transplacental exposure to cypermethrin can induce low levels of DNA damage in fetuses. This observation could be an explanation for the teratogenic effect exhibited by this chemical in many other studies. The results indicate that cypermethrin may be transplacentally genotoxic. The authors propose more detailed investigations for validating the current findings.

Toxicopathological effects of lambda-cyhalothrin in female rabbits (Oryctolagus cuniculus)

The aim of this study was to investigate effects of lambda-cyhalothrin (LCT) on clinical, hematological, biochemical and pathological alterations in rabbits (Oryctolagus cuniculus). New Zealand white female rabbits (n = 24) of 4-5 months age having 997.92 ± 32.83 g weight were divided into four equal groups. Group A (control) received normal saline intraperitoneally (ip). Animals in groups B, C and D were treated with LCT 1.0, 4.0 and 8.0 mg/kg bw ip. Each group received seven consecutive doses at an interval of 48 hours. Blood and serum samples were collected at an interval of 96 hours. Blood analysis revealed a significant (p < 0.05) decrease in red blood cell and white blood cell counts, hemoglobin concentration and lymphocytes, while mean corpuscular hemoglobin concentration, mean corpuscular volume, neutrophils, monocytes and eosinophils were increased. Serum biochemical analysis revealed significant (p < 0.05) decrease in serum total proteins and serum albumin, while an increase was seen in serum alanine aminotransferase and aspartate aminotransferase activities compared with the control group. Serum globulin values varied non-significantly in all treatment groups as compared to control group. A dose-dependent increase in the incidence of micronucleated polychromatic erythrocyte was observed. All gross and histopathological lesions observed in LCT-treated rabbits were dose-dependent. Liver of the treated rabbits exhibited extensive perihepatitis, hyperplasia of bile duct, necrosis, hemorrhages and congestion. In lungs, there were hemorrhages, thickened alveolar walls, congestion, emphysema, collapsed alveoli and accumulation of extensive inflammatory cells. Kidneys were congested and hemorrhagic whereas renal parenchyma and stroma were normal. Microscopically, heart showed congestion of blood vessels and nuclear pyknosis, myodegeneration. It was concluded from the study that LCT produced toxicopathological alterations in rabbits in a dose-dependent manner. On the basis of the results, it can be suggested that overdosing of LCT be avoided while treating animals for ectoparasites.

A review of conflict of interest, competing interest, and bias for toxicologists

One of the issues often associated with scientific misconduct is conflict of interest. Although there is a lack of uniformity in the definition of conflict of interest, many express concerns that competing interests may bias research methods and the interpretation of data and conclusions. In extreme cases, conflict of interest activity could contribute to scientific misconduct, hinder the training of scientists, delay the dissemination of research results, lead to the harming of human health and the environment, and misdirect society's decisions that rely on science. This article is not a commentary or editorial but an attempt to supply an overview of what has been said, researched, and accomplished in the area of conflict of interest for toxicologists. Discussion of the financial, professional, and philosophical concerns associated with conflict of interest will be followed by brief discussion of general management approaches and the roles of scientists and organizations from all sectors (i.e., academia, industry, non-profit organizations, and government).

Genotoxicity induced by pesticide mixtures: in-vitro studies on human peripheral blood lymphocytes

To assess the damage caused by pesticides and their mixtures on humans, we designed in-vitro experiments to evaluate their cytotoxicity and genotoxicity. Three equimolar pesticide mixtures were investigated for their capability to affect cultured human peripheral blood lymphocytes. The LC50 values for cytotoxicity, using standard trypan blue dye exclusion and calculated by probit analysis, were 4.18, 5.76, and 7.5 microM for endosulfan, carbofuran, and monocrotophos, respectively. When combined in equimolar concentrations, the LC50 values for cytotoxicity were 0.7, 0.9, and 1.0 microM for monocrotophos + carbofuran, endosulfan + monocrotophos, and endosulfan + carbofuran, respectively, using the method. DNA damage was estimated using chromosomal aberrations (chromatid breaks, fragments, gaps, aneuploidy, and satellite association) and comet assays using 1/10 of the LC50 concentrations. Using a standard alkaline comet assay procedure, high concentrations of individual pesticides (0.5-4.0 microM) caused significant DNA damage as indicated by visible tail lengths. Lower concentrations (0.05-0.5 microM) of their binary mixtures could cause the same effect. The results suggest that analysis of genotoxicity may serve as an important biomarker for occupational and household exposure to pesticides, especially mixtures of pesticides, with different modes of action.

An evaluation of the mode of action framework for mutagenic carcinogens case study: Cyclophosphamide

In response to the 2005 revised US Environmental Protection Agency (EPA) Cancer Guidelines, a Risk Assessment Forum's Technical Panel has devised a strategy in which genetic toxicology data combined with other information are assessed to determine whether a carcinogen operates through a mutagenic mode of action (MOA). This information is necessary for EPA to decide whether age-dependent adjustment factors (ADAFs) should be applied to the cancer risk assessment. A decision tree has been developed as a part of this approach and outlines the critical steps for analyzing a compound for carcinogenicity through a mutagenic MOA (e.g., data analysis, determination of mutagenicity in animals and in humans). Agents, showing mutagenicity in animals and humans, proceed through the Agency's framework analysis for MOAs. Cyclophosphamide (CP), an antineoplastic agent, which is carcinogenic in animals and humans and mutagenic in vitro and in vivo, was selected as a case study to illustrate how the framework analysis would be applied to prove that a carcinogen operates through a mutagenic MOA. Consistent positive results have been seen for mutagenic activity in numerous in vitro assays, in animals (mice, rats, and hamsters) and in humans. Accordingly, CP was processed through the framework analysis and key steps leading to tumor formation were identified as follows: metabolism of the parent compound to alkylating metabolites, DNA damage followed by induction of multiple adverse genetic events, cell proliferation, and bladder tumors. Genetic changes in rats (sister chromatid exchanges at 0.62 mg/kg) can commence within 30 min and in cancer patients, chromosome aberrations at 35 mg/kg are seen by 1 hr, well within the timeframe and tumorigenic dose range for early events. Supporting evidence is also found for cell proliferation, indicating that mutagenicity, associated with cytotoxicity, leads to a proliferative response, which occurs early (48 hr) in the process of tumor induction. Overall, the weight of evidence evaluation supports CP acting through a mutagenic MOA. In addition, no data were found that an alternative MOA might be operative. Therefore, the cancer guidelines recommend a linear extrapolation for the risk assessment. Additionally, data exist showing that CP induces mutagenicity in fetal blood and in the peripheral blood of pediatric patients; thus, the ADAFs would be applied.

GSTP1 Genetic Polymorphism Is Associated with a Higher Risk of DNA Damage in Pesticide-Exposed Fruit Growers

Pesticide exposure is associated with various neoplastic diseases and congenital malformations. Animal studies also indicated that pesticides may be metabolized by cytochrome P450 3A5 (CYP3A5) enzymes, paraoxonases (PON1 and PON2), or glutathione S-transferases (GSTM1, GSTT1, and GSTP1). However, little is known about the genotoxicity of pesticides in people with various genetic polymorphisms of human CYP3A5, PON1, PON2, GSTM1, GSTT1, and GSTP1. Thus, this study was designed to investigate whether various metabolic genotypes are more susceptible to DNA damage in pesticide-exposed fruit growers. Using the Comet assay, the extent of DNA damage was evaluated in the peripheral blood of 91 fruit growers who experienced pesticide exposure and 106 unexposed controls. Questionnaires were administered to obtain demographic data, cigarette smoking habits, medical, and occupational histories. The genotypes for CYP3A5, PON1, PON2, GSTM1, GSTT1, and GSTP1 genes were identified by PCR. The results showed that subjects experiencing high or low pesticide exposure had a significantly greater DNA tail moment (DAN damage) than did controls. The multiple regression model also revealed that age (P < 0.01), high pesticide exposure (P < 0.01), low pesticide-exposure (P < 0.01), and CYP3A5 (P = 0.04) and GSTP1 (P = 0.02) genotypes were significantly associated with an increased DNA tail moment. Further analysis of environmental and genetic interactions revealed a significant interaction for GSTP1 genotypes to influence DNA tail moment for the high pesticide exposure group. These results suggest that individuals with susceptible metabolic GSTP1 genotypes may experience an increased risk of DNA damage elicited by pesticide exposure.

Embryotoxicity of oral administered chlorothalonil in mice

BACKGROUND

Chlorothalonil (2,4,5,6-tetrachloroisophthalonitril), the nephrotoxic fungicide, was examined for its potential to produce developmental toxicity in mice after oral administration.

METHODS

Pregnant ICR (CD-1) mice were given sublethal doses of 0 (corn oil), 100, 400, and 600 mg/kg/day chlorothalonil by gavage on gestation days (GD) 6-15.

RESULTS

Maternal effects in 400 and 600 mg/kg/day dose groups included signs of toxicity such as weakness and depression in the maternal activity, and reduction in body weight and weight gain. No maternal toxicity was apparent in the 100 mg/kg/day dose group. Maternal exposure to chlorothalonil during organogenesis significantly affected the number of live fetuses, early resorption, and mean fetal weight in the 400 and 600 mg/kg/day dose groups. No external, visceral, and skeletal abnormalities were observed among any of the treated groups compared to the control.

CONCLUSIONS

On the basis of the present results chlorothalonil can produce clinical signs of toxicity and fetotoxicity without teratogenic effects at 400 and 600 mg/kg/day dose groups.

A risk assessment of atrazine use in California: human health and ecological aspects

A risk assessment of the triazine herbicide atrazine has been conducted by first analyzing the toxicity database and subsequently estimating exposure. Margins of safety (MOS) were then calculated. Toxicity was assessed in animal studies and exposure was estimated from occupational and dietary sources. In acute toxicity studies, atrazine caused developmental toxicity in the rabbit [no observed effect level (NOEL) 5 mg kg(-1) day(-1)] and cardiotoxicity in a dog chronic study (NOEL 0.5 mg kg(-1) day(-1)); cancer (mammary glands) resulted from lifetime exposure. The mammary tumors, which occurred specifically in female Sprague-Dawley rats, were malignant, increased in a dose-dependent manner and were also observed with other, related triazines. Evidence for a genotoxic basis for these tumors was either equivocal or negative. Triazines have been shown to be clastogenic in Chinese hamster ovary cells, in vitro, but without showing a convincing dose/response relationship. Atrazine can be converted into genotoxic N-nitrosoatrazine in the environment or the digestive system, suggesting that N-nitrosamines derived from triazines could be oncogenic. However, it was concluded that N-nitrosotriazines are unlikely to play a significant role in triazine-induced rat mammary gland tumors. An endocrine basis for the mammary tumors, involving premature aging of the female SD rat reproductive system, has been proposed. A suppression of the luteinizing hormone surge during the estrus cycle by atrazine leads to the maintenance of elevated blood levels of 17beta-estradiol (E2) and prolactin. The mechanism for tumor development may include one or more of the following: the induction of aromatase (CYP19) and/or other P450 oxygenases, an antagonist action at the estrogen feedback receptor in the hypothalamus, an agonist action at the mammary gland estrogen receptor or an effect on adrenergic neurons in the hypothalamic-pituitary pathway. None of these has been excluded as a target because there has been a lack of a rigorous attempt to address the mechanism of action for mammary tumors at the molecular level. The potential occupational exposure to atrazine was assessed during mixing, loading and application. Absorbed daily dosage values were 1.8-6.1 microg kg(-1) day(-1). The MOS values (animal NOEL/human exposure) for short-term (acute) exposure were 820-2800. Longer-term occupational exposure and risk were also calculated. Detectable crop residues are generally absent at harvest. Theoretical calculations of acute dietary exposure used tolerance levels, along with secondary residues, and water, for which there is a maximum contamination level; atrazine plus the three main chlorotriazine metabolites were combined. MOS values were above 2000 for all population subgroups. Dietary exposure to atrazine is therefore extremely unlikely to result in human health hazard. Recent publications have reported a possible feminization of frogs, measured in laboratory and field studies. This is assumed to be due to the induction of aromatase, but no measurements of enzyme activity have been reported. In field studies, the water bodies with the greatest numbers of deformed frogs sometimes had the lowest concentrations of atrazine. Other studies have also cast doubt on the feminization theory, except perhaps at very high levels of atrazine. Epidemiology studies have investigated the possibility that atrazine may result in adverse effects in humans. Although some studies have claimed that atrazine exposure results in an elevated risk of prostate cancer, the published literature is inconclusive with respect to cancer incidence.

Effects of pesticides on human peripheral lymphocytes in vitro: induction of DNA damage

Because of the widespread use of pesticides for domestic and industrial applications the evaluation of their genotoxic effects is of major concern to public health. Although various experimental data have provided evidence that pesticides can possess genotoxic properties in animals and in in vitro test systems after acute and chronic exposure, the information on the genotoxic effects of some of pesticides is limited and inconsistent. In the present study, the genotoxic potential of commonly used pesticides (i.e., dimethoate and methyl parathion from the organophosphate class, propoxur and pirimicarb from carbamates, and cypermethrin and permethrin from pyrethroids) have been evaluated. The genotoxic effects of these substances were examined using the single cell gel electrophoresis (comet) assay in freshly isolated human peripheral lymphocytes. The cells were incubated with 10, 50, 100 and 200 microg/ml concentrations of the test substances for 0.5 h at 37 degrees C and DNA damage was compared with that obtained in lymphocytes from the same donor not treated with substances. Hydrogen peroxide, 100 microM, was used as a positive control. Within the concentration ranges studied, no significant cytotoxic effects were observed. Dimethoate and methyl parathion at 100 and 200 microg/ml; propoxur at 50, 100 and 200 microg/ml, and pirimicarb, cypermethrin and permethrin at 200 microg/ml significantly increased DNA damage in human lymphocytes.

Carcinogenic and genotoxic potential of turf pesticides commonly used on golf courses

As a result of the controversy surrounding pesticide use and animal and human health concerns, many municipalities in Canada have restricted, or are in the midst of restricting, the use of pesticides for cosmetic purposes. In some cases, pesticide use on golf courses is also being phased out at the municipal level. One of the dominant health effects of concern in relation to pesticide exposure is the occurrence of cancer. With over 1600 golf courses in Canada and between 400 and 600 new courses created each year in Canada and the United States, there appears to be increasing potential for unintentional human and animal exposure to turf pesticides. In light of the debate around pesticide exposure and the onset of cancer that has lead to controversial Canadian municipal bylaws regulating pesticide use, and due to recent results of a biomonitoring study that has shown genotoxicity in a rodent species living in golf-courses, it seems timely to review the carcinogenic and genotoxic potential of commonly used golf-course pesticides. The purpose of this review is to present some debated epidemiological research that deals with the relationship between pesticide exposure and cancer, and to review and update the literature on the in vivo and in vitro mammalian carcinogenic and genotoxic potential of these pesticides. It is our intention to unite information from various sources so those interested specifically in the carcinogenicity and genotoxicity of pesticides commonly used on golf courses can refer to one comprehensive and updated resource.

Cytogenetic biomonitoring of a floriculturist population in Italy: micronucleus analysis by fluorescence in situ hybridization (FISH) with an all-chromosome centromeric probe

Flower production in greenhouses associated with a heavy use of pesticides is very wide-spread in the western part of the Ligurian region (Italy). The formation of micronuclei in peripheral blood lymphocytes is a valuable cytogenetic biomarker in human populations occupationally exposed to genotoxic compounds. In the present study we investigated the micronucleus frequency in peripheral blood lymphocytes of 52 floriculturists and 24 control subjects by use of the cytokinesis-block methodology associated with fluorescence in situ hybridization with a pan-centromeric probe that allowed to distinguish centromere-positive (C+) and centromere-negative (C-) micronuclei. The comparison between floriculturists and controls did not reveal any statistically significant difference in micronucleus frequency, although an increase was observed with increasing pesticide use, number of genotoxic pesticides used and duration of exposure. An increase in C+ as well as in C- micronuclei and in the percentage of C+ micronuclei with respect to the total number of micronuclei was detected in floriculturists, suggesting a higher contribution of C+ micronuclei in the total number scored. The percentage C+ micronuclei was not related to the duration of exposure or to the number of genotoxic pesticides used, but a higher percentage (66.52% versus 63.78%) was observed in a subgroup of subjects using benzimidazolic compounds, compared with the floriculturist population exposed to a complex pesticide mixture not including benzimidazolics. These results suggest a potential human hazard associated with the exposure to this class of aneuploidy-inducing carcinogens.

Genotoxicity of pesticides: a review of human biomonitoring studies

Pesticides constitute a heterogeneous category of chemicals specifically designed for the control of pests, weeds or plant diseases. Pesticides have been considered potential chemical mutagens: experimental data revealed that various agrochemical ingredients possess mutagenic properties inducing mutations, chromosomal alterations or DNA damage. Biological monitoring provides a useful tool to estimate the genetic risk deriving from an integrated exposure to a complex mixture of chemicals. Studies available in scientific literature have essentially focused on cytogenetic end-points to evaluate the potential genotoxicity of pesticides in occupationally exposed populations, including pesticide manufacturing workers, pesticide applicators, floriculturists and farm workers. A positive association between occupational exposure to complex pesticide mixtures and the presence of chromosomal aberrations (CA), sister-chromatid exchanges (SCE) and micronuclei (MN) has been detected in the majority of the studies, although a number of these failed to detect cytogenetic damage. Conflicting results from cytogenetic studies reflect the heterogeneity of the groups studied with regard to chemicals used and exposure conditions. Genetic damage associated with pesticides occurs in human populations subject to high exposure levels due to intensive use, misuse or failure of control measures. The majority of studies on cytogenetic biomarkers in pesticide-exposed workers have indicated some dose-dependent effects, with increasing duration or intensity of exposure. Chromosomal damage induced by pesticides appears to have been transient in acute or discontinuous exposure, but cumulative in continuous exposure to complex agrochemical mixtures. Data available at present on the effect of genetic polymorphism on susceptibility to pesticides does not allow any conclusion.

Assessment of genotoxic effects of chloropyriphos and acephate by the comet assay in mice leucocytes

Two organophosphorus (OP) pesticides (chloropyriphos and acephate) and cyclophosphamide (CP) (positive control) were tested for their ability to induce in vivo genotoxic effect in leucocytes of Swiss albino mice using the single cell gel electrophoresis assay or comet assay. The mice were administered orally with doses ranging from 0.28 to 8.96 mg/kg body weight (b. wt.) of chloropyriphos and 12.25 to 392.00 mg/kg b.wt. of acephate. The assay was performed on whole blood at 24, 48, 72 and 96 h. A significant increase in mean comet tail length indicating DNA damage was observed at 24h post-treatment (P<0.05) with both pesticides in comparison to control. The damage was dose related. The mean comet tail length revealed a clear dose dependent increase. From 48 h post-treatment, a gradual decrease in mean tail length was noted. By 96 h of post-treatment the mean comet tail length reached control levels indicating repair of the damaged DNA. From the study it can be concluded that the comet assay is a sensitive assay for the detection of genotoxicity caused by pesticides.

Detection of DNA damage in mouse peripheral blood leukocytes by the comet assay after oral administration of monocrotophos

The objective of this study was to determine if single/double strand DNA breaks could be induced by monocrotophos (organophosphorus pesticide) in mice in vivo using the comet assay. Mice were dosed orally with 0.046, 0.093, 0.186, 0.373 and 0.746 mg/kg body weight of monocrotophos, and the assay was performed on whole blood after 24, 48 and 72 h. A significant increase in mean comet tail length indicating DNA damage was observed at 24 and 48 h post-treatment with monocrotophos when compared to controls. A decrease in the mean tail length was observed at 72 h post-treatment indicating repair of the damaged DNA. The mean tail length showed a dose-related increase and time dependent decrease. The study reveals that comet assay is a sensitive and rapid method to detect genotoxicity of monocrotophos.

A survey of EPA/OPP and open literature on selected pesticide chemicals. II. Mutagenicity and carcinogenicity of selected chloroacetanilides and related compounds

With this effort, we continue our examination of data on selected pesticide chemicals and their related analogues that have been presented to the U.S. Environmental Protection Agency's (USEPA's) Office of Pesticide Programs (OPP). This report focuses on a group of selected chloroacetanilides and a few related compounds. As part of the registration process for pesticidal chemicals, interested parties (registrants) must submit toxicity information to support the registration including both mutagenicity and carcinogenicity data. Although this information is available to the public via Freedom of Information (FOI) requests to the OPP, publication in the scientific literature allows greater dissemination and examination of the data. For this Special Issue, graphic profiles have been prepared of the mutagenicity and carcinogenicity data available in the submissions to OPP. Also, a discussion is presented about how toxicity data are used to help establish tolerances (limits of pesticide residues in foods). The mutagenicity results submitted by registrants are supplemented by data on these chemicals from the open literature to provide a full perspective of their genetic toxicology. The group of chloroacetanilides reviewed here display a consistent pattern of mutagenic activity, probably mediated via metabolites. This mutagenic activity is a mechanistically plausible factor in the development of tumors seen in experimental animals exposed to this class of chemicals.

Chlorothalonil: lack of genotoxic potential

Based upon analyses using a number of validated structure-activity relationship models, it is concluded that the carcinogenicity in rodents of chlorothalonil is not due to a genotoxic mechanism.

DNA damaging effects of pesticides measured by the single cell gel electrophoresis assay (comet assay) and the chromosomal aberration test, in CHOK1 cells

One herbicide (isoproturon), two fungicides (carbendazim and chlorothalonil) and etoposide (an effective antitumor agent used as a positive control), were tested for their ability to induce cytotoxic and genotoxic effects in Chinese Hamster Ovary (CHOK1) cells. Etoposide induced DNA damage detectable both by the alkaline Single Cell Gel Electrophoresis (SCGE) assay and the chromosomal aberration (CA) test in absence of noticeable cytotoxicity. With the SCGE assay, a clear induction of DNA damage was observed for chlorothalonil within a 0.2 to 1 microM concentration range. In the CA test, chlorothalonil gave also positive results, inducing mainly chromosome breaks. In contrast, no DNA damage was observed with the SCGE assay for carbendazim and isoproturon. In the CA test, carbendazim induced only numerical aberrations in the concentration range of 25 microM to 100 microM, and isoproturon did not induce any significant increase in CA. In conclusion, chlorothalonil appears genotoxic in proliferative CHOK1 cells, and as expected, the aneugenic compound, carbendazim, did not induce DNA strand breaks in the SCGE assay.

Lack of genotoxicity of the herbicide atrazine in cultured human lymphocytes

The widely used herbicide atrazine was evaluated for genotoxicity in cultured human peripheral blood lymphocytes. Sister-chromatid exchanges (SCE), chromosome aberrations (CA) and micronuclei (MN) were scored as genetic endpoints. To detect eventual metabolic modification in the genotoxicity of this herbicide, the cultures of SCE and MN demonstration were also treated with S9 microsomal fraction. From our results we can conclude that atrazine was able to exert a weak cytotoxic effect. However, the overall evaluation of the genotoxicity data indicate that this herbicide is not effective in the three assays conducted, irrespective of the presence of metabolic activation, which would mean a general lack of effectiveness of atrazine to induce clastogenic and aneugenic damage in cultured human lymphocytes.

Dominant lethal test with rats exposed to 1,3-dichloropropene by inhalation

The potential of 1,3-dichloropropene (1,3-DCP) to induce dominant lethal mutations in the germ cells of male CD rats following inhalation exposure was investigated. Groups of 11-week-old males (30 animals/group) were exposed to 1,3-DCP vapors by inhalation at targeted concentrations of 0 (negative control), 10, 60, and 150 ppm for 10 weeks (6 hr/day, 7 days/week). An additional group of 30 males (designated the pairfed group) was kept on dietary restriction for 10 weeks. This group served as a control for any effects of decreased feed consumption and the associated body weight loss on the dominant lethal indices in the males exposed to 1,3-DCP. At the termination of the exposures, each male was cohoused with naive adult virgin CD females for two consecutive mating trials (1 week/trial, 2 females/male). Females were necropsied 13 days after the conclusion of each weekly mating trial and the number of corpora lutea, live implantations, and resorptions were determined. There were no statistically significant increases in either the pre- or postimplantation embryonic/fetal loss in females mated with 1,3-DCP-exposed males relative to controls at any weekly mating period. Based on these results, it can be concluded that 1,3-DCP is not mutagenic to the male germ cells of CD rats at exposure levels < or = 150 ppm, the highest concentration tested.

Dairy cattle as a bioindicator of exposure to genotoxic substances in a heavily polluted area in northern Bohemia

The exposure of dairy cattle to genotoxic agents in two districts with different levels of environmental pollution was estimated using cytogenetic analysis of bovine peripheral lymphocytes. The Teplice district represented an industrialized area where the air pollution rate is extremely high mainly in the winter, and the Prachatice district--an agricultural area with a relatively low level of pollution. The Ames test was used to examine feed samples for the content of mutagenic substances. Cows in the Teplice district showed a significantly higher count of aberrant cells (4.83 +/- 2.36) than cows in the Prachatice district (3.63 +/- 2.12). The sum of revertants induced by rinsings or extracts of feeds in both of the two test strains (Salmonella typhimurium TA 98 and TA 100) was significantly higher in the district of Teplice than in the district of Prachatice. The percentages of findings with mutagenic responses were 56.3 and 34.8% for the districts of Teplice and Prachatice, respectively. No mutagenic activity was found in milk samples collected in any of the districts. Apparently, the cows kept in the Teplice district were more exposed to genotoxic substances than the cows in the Prachatice district. The major source of this exposure was probably fresh fodder contaminated by industrial emissions.

Assessment of DNA damage induced in vitro by etoposide and two fungicides (carbendazim and chlorothalonil) in human lymphocytes with the comet assay

The effects of two fungicides (carbendazim and chlorothalonil) on the induction of DNA damage in human peripheral blood lymphocytes (human PBL) have been investigated using the single cell gel electrophoresis assay (SCGE assay or comet assay) immediately after a 1-h treatment and after a 24-h post-treatment incubation. The assessment of etoposide (an effective antitumour agent) effects on human PBL in terms of cell viability and dose-DNA damage relationships was made and etoposide selected as a positive control. The results indicate that etoposide induces significant (p < 0.01) dose-dependent DNA damages for concentrations at which the loss of cell viability is low. After a 24-h recuperation period, all observed DNA damages has disappeared. With SCGE assay performed after a 1-h treatment, similar positive results were observed with chlorothalonil alone or in association with carbendazim, without any loss of cell viability. However, a dramatic loss of cell viability was measured after 24 h and was associated with a large proportion of highly damaged cells. In contrast, carbendazim was not cytotoxic on human PBL and did not induced DNA damage using the SCGE assay either immediately after treatment or after a 24-h post-treatment incubation. These results point to the necessity of an adequate evaluation of immediate and long-term cytotoxicity of compounds that are to be assessed by the SCGE assay.

Inhibition of erythrocyte membrane (Ca2+ + Mg2+)-ATPase by the organophosphorus insecticides parathion and methylparathion

Organophosphorus insecticides parathion and methylparathion non-competitively inhibited the activity of (Ca2+ + Mg2+)-ATPase bound to and solubilized from pig erythrocyte membrane. Both enzyme preparations exhibited biphasic substrate curves displaying the existence of two functional active sites with low and high affinity to ATP. Also, the relationship between the activity of bound enzyme and Ca2+ concentration was biphasic. The activity reached maximum at 20 microM then dropped progressively as the Ca2+ concentration was raised. The inhibition of the activity was more pronounced for parathion than for methylparathion and the solubilized enzyme preparation was more affected than the bound one. The inhibition constants (Ki) for parathion for bound enzyme were 55 and 158 microM for high- and low-affinity active sites, respectively; for methylparathion these values equalled 74 and 263 microM, respectively. Ki values for parathion were 36 and 118 microM for solubilized enzyme (high- and low-affinity sites, respectively), for methylparathion -62 and 166 microM, respectively. The magnitude of the effect was greater for a low Ca2+ concentration, which could arise from different conformational states of the enzyme at different calcium concentrations. The results of the experiment suggest that the insecticides inhibited the ATPase by binding to a site on the enzyme rather than by the interaction with associated lipids, although lipids could weaken the action of the compounds due to the strong affinity of organophosphorus insecticides to lipids.

Development and impact of the Gene-Tox-Program, genetic activity profiles, and their computerized data bases

This invited historical review traces the development and impact of two major data bases in the field of genetic toxicology. Discussed from a personal perspective are the Environmental Protection Agency (EPA) Gene-Tox Program and the EPA/International Agency for Research on Cancer Genetic Activity Profiles (GAPs) and their respective data bases. Whereas Gene-Tox was focused on the assessment of short-term tests and their role in predicting carcinogens and mutagens, GAPs and the GAP data base were designed specifically to aid in the evaluation of individual chemicals. Both data bases have been computerized. Gene-Tox is available on TOXNET and GAP is available in a personal computer format from the author. The Gene-Tox and GAP data bases appear to have had substantial impact, particularly on hazard identification activities in cancer risk assessment.