Evaluation of beta-naphthoxyacetic acid for mutagenic activity in the Salmonella/mammalian microsome assay

Beta-naphthoxyacetic acid (BNOA) is used as a plant growth regulator on tomatoes and strawberries. It is the active ingredient in Blossom-Set and Berry-Set, two plant hormone sprays for fruit-set. The mutagenic activity of BNOA was evaluated in four strains of Salmonella typhimurium (TA97, TA98, TA100 and TA1535) in the presence and absence of liver microsomal and cytosolic enzymes derived from Aroclor induced rats. BNOA did not produce any significant increase (p less than 0.05) in the reversion of any of the four tester strains in the standard plate incorporation assay. Results of the agar overlay toxicity tests indicates that the chemical shows toxic effects at concentrations above 500 micrograms/plate. It was concluded that under the conditions of these tests, BNOA did not exhibit any mutagenic activity.     

Evaluation of chlordimeform and degradation products for mutagenic and DNA-damaging activity in Salmonella typhimurium and Escherichia coli

The mutagenic activity of chlordimeform and two of its breakdown products, 4-chloro-o-toludine and 4-chloro-N-formyl-o-toluidine were determined with five histidine dependent strains of Salmonella typhimurium (TA1535, TA1537, TA1538, TA98, TA100) and five tryptophan dependent strains of E. coli WP2 (WP2, WP2uvrA, WP67, CM611, CM571) with and without rat liver microsomal enzymes. 4-chloro-o-toluidine increased the number of the reversions of the S. typhimurium strain TA1535 more than two fold over spontaneous at the concentration of 400 micrograms/plate. The results of the DNA repair tests in the Salmonella TA1538/TA1978 and E. coli multirepair deficient systems showed that both breakdown products were active in inducing damage not repaired in at least one repair deficient strain while chlordimeform itself was inactive.     

Screening pesticides for their ability to damage bacterial DNA

Twenty-six pesticides and pesticide degradation products were screened (125 micrograms - 2000 micrograms) for their ability to induce unrepairable damage to bacterial DNA. Three repair test systems were utilized in this study, the Salmonella typhimurium (TA1538/TA1978), the E. coli K-12 (Pol A1+/Pol1-) and the E. coli WP2 (WP2, WP2uvrA, WP67, CM611 and CM571). Aldicarb (1000 micrograms), benomyl (250 micrograms), 2-aminobenzimidazole (2000 micrograms), captan (125 micrograms), fenazalor (500 micrograms), 5,6-dichloro-2-trifluoromethylbenzimidazole (NC-2983) (250 micrograms), isothymol (250 micrograms), maleic hydrazide (1000 micrograms), pentachloronitrobenzene (1000 micrograms) were DNA-damaging to one or more bacterial test systems. Isothymol and NC-2983 affected all three test systems. Chlorinated hydrocarbon insecticides, some being recognized as carcinogens, did not produce a zone of inhibition in any of the tester strains possibly due to their poor solubility and diffusion in the agar overlay. It was concluded that these tests can be performed along with bacterial reversion tests to complement each other as short-term screening tests for potential carcinogens and mutagens.     

Genotoxicity of methyl parathion in short-term bacterial test systems

Genotoxicity of the insecticide methyl parathion was investigated in Salmonella typhimurium and Escherichia coli bacterial test systems for the detection of back mutations and DNA-damage. Methyl parathion was mutagenic to S. typhimurium strain TA100 after activation with rat liver microsomal and cytosolic enzymes. In DNA repair tests, methyl parathion was effective in inducing damage to the S. typhimurium strain TA1538 which lack excision repair compared to the strain TA1978 which is proficient in excision repair mechanisms. Normal laboratory light conditions had no effect on the mutagenicity tests, however, exposure of methyl parathion in the petri dish containing the tester strain TA100 and rat liver microsomal and cytosolic enzymes reduced the mutagenic activity and increased the toxic effects of methyl parathion.     

Evaluation of chlordimeform and degradation products for mutagenic and DNA‐damaging activity in salmonella typhimurium and escherichia coli

Abstract

The mutagenic activity of chlordimeform and two of its breakdown products, 4‐chloro‐o‐toludine and 4‐chloro‐N‐formyl‐o‐toluidine were determined with five histidine dependent strains of Salmonella typhimurium (TA1535, TA1537, TA1538, TA98, TA100) and five tryptophan dependent strains of E. coli WP₂. (WP₂, WP₂uvrA, WP67, CM611, CM571) with and without rat liver microsomal enzymes. 4‐chloro‐o‐toluidine increased the number of the reversions of the S. typhimurium strain TA1535 more than two fold over spontaneous at the concentration of 400 μg/plate.

The results of the DNA repair tests in the Salmonella TA1538/TA1978 and E. coli multirepair deficient systems showed that both breakdown products were active in inducing damage not repaired in at least one repair deficient strain while chlordimeform itself was inactive.     

Genotoxicity of methyl parathion in short‐term bacterial test systems

Abstract

Genotoxicity of the insecticide methyl parathion was investigated in Salmonella typhimurium and Escherichia coli bacterial test systems for the detection of back mutations and DNA‐damage. Methyl parathion was mutagenic to S. typhimurium strain TA100 after activation with rat liver microsomal and cytosolic enzymes. In DNA repair tests, methyl parathion was effective in inducing damage to the S. typhimurium strain TA1538 which lack excision repair compared to the strain TA1978 which is proficient in excision repair mechanisms. Normal laboratory light conditions had no effect on the mutagenicity tests, however, exposure of methyl parathion in the petri dish containing the tester strain TA100 and rat liver microsomal and cytosolic enzymes reduced the mutagenic activity and increased the toxic effects of methyl parathion.     

The aqueous sulfite-nitrite system: Investigations on the mutagenicity of some known products

Some known reaction products of the two commonly used food additives, sulfite and nitrite, were examined for mutagenicity using the Salmonella/mammalian-microsome test. Potassium nitrosodisulfonate, potassium aminetrisulfonate and potassium hydroxylaminemonosulfonate were not mutagenic over a dose range of 0.01 – 10 mg/plate in the strains his G 46, TA 100 and TA 98. Potassium hydroxylaminedisulfonate showed a weak mutagenic activity in his G 46 and TA 100 with microsomal activation. Hydroxylamine-O-sulfonic acid was only weakly mutagenic in the excision-repair proficient strain his G 46 in the presence of S9.     

Screening pesticides for their ability to damage bacterial DNA

Abstract

Twenty‐six pesticides and pesticide degradation products were screened (125 μg ‐ 2000 μg) for their ability to induce unrepairable damage to bacterial DNA. Three repair test systems were utilized in this study, the Salmonella typhimurium (TA1538/TA1978), the E. coli K‐12 (Pol A₁ ⁺/Pol^‐ ₁) and the E. coli WP₂ (WP₂, WP₂ uvrA, WP67, CM611 and CM571). Aldicarb (1000 μg), benomyl (250 μg), 2‐aminobenzimidazole (2000 μg), captan (125 μg), fenazalor (500 μg), 5,6‐dichloro‐2‐trifluoromethylbenzimida‐zole (NC‐2983) (250 μg), isothymol (250 μg), maleic hydrazide(1000 μg), pentachloronitrobenzene (1000 μg) were DNA‐damaglng to one or more bacterial test systems. Isothymol and NC‐2983 affected all three test systems. Chlorinated hydrocarbon insec ticides, some being recognized as carcinogens, did not: produce a zone of inhibition in any of the tester strains possibly due to their poor solubility and diffusion in the agar overlay. It was concluded that these tests can be performed along with bacterial reversion tests to complement each other as short‐term screening tests for potential carcinogens and mutagens.     

Potential of 2,4-dichlorophenoxyacetic acid conjugates as promutagens in the Salmonella/microsome mutagenicity test

Hepatic S9 preparations from Aroclor 1254 induced rats and 3-methylcholanthrene induced woodchucks were used to investigate, in vitro, the mutagenic potential of five amino acid conjugates of 2,4-Dichlorophenoxyacetic acid (alanine, aspartic acid, leucine, methionine and tryptophan). Five strains of Salmonella typhimurium (TA97, TA98, TA100, TA1535, TA1538) were utilized for this purpose. Dose-response effects producing a two-fold increase of revertants over spontaneous levels were not observed with either S9 preparation indicating that the amino acid conjugates are not promutagens in these assays.     

Fate of mutagenicity produced during anaerobic biodegradation of the herbicide chlornitrofen (CNP)

The mutagenicity of chlornitrofen (CNP)-containing solutions has been reported to increase during anaerobic biodegradation. In the present study, the fate of this increased mutagenicity under subsequent aerobic and anaerobic incubation conditions was investigated using two Salmonella tester strains, YG 1024 (a frameshift-detecting strain) and YG 1029 (a base-pair-substitution-detecting strain). Mutagenicity for both YG 1024 and YG 1029 strains increased during nine-day anaerobic biodegradation. During subsequent anaerobic incubation, the increased mutagenicity decreased gradually for YG 1029 but did not change significantly for YG 1024. By contrast, the increased mutagenicity decreased rapidly after the conversion to aerobic incubation for both YG 1024 and YG 1029 strains. The rapid decrease in mutagenicity during aerobic incubation was due to decreases, not only in an identified mutagenic metabolite (CNP-amino) but also in unidentified mutagenic metabolites.     

Use of semi-permeable membrane devices to monitor pollutants in water and assess their effects: a laboratory test and field verification

Uptake of eight pesticides of different classes (organochlorines, synthetic pyrethroids, dinitroanilines, amides) by semi-permeable membrane devices (SPMDs) was studied in a laboratory continuous-flow system. After 20 days of exposure, membrane concentration factors were in the range of 50 000-120 000 for all the analytes except for the amide herbicides propachlor and alachlor, which were not detected in any of the SPMDs. The kinetic data and mathematical models were used to calculate analyte uptake rate constants, SPMD lipid/water partition coefficients, average sampling rates and concentrations of the pesticides in water. To assess the effects of concentrated pesticides, standard bioassays (Salmonella/histidine reversion assay and bioluminescence inhibition in Vibrio fischeri test) were incorporated in the SPMD technique. To test the method in an environmental situation, SPMDs were deployed in polluted sites in Lithuania. Polynuclear aromatic hydrocarbons were the major pollutants detected in the SPMDs deployed in the field. All the SPMD dialysates were highly toxic in the bioluminescence inhibition test but no mutagenic activity was observed in the Salmonella/histidine reversion assay.     

Potential of 2, 4‐dichlorophenoxyacetic acid conjugates as promutagens in the salmonella/microsome mutagenicity test

Abstract

Hepatic S9 preparations from Aroclor 1254 induced rats and 3‐methylcholanthrene induced woodchucks were used to investigate, in vitro, the mutagenic potential of five amino acid conjugates of 2, 4‐Dichlorophenoxyacetic acid (alanine, aspartic acid, leucine, methionine and tryptophan). Five strains of Salmonella typhimurium (TA97, TA98, TA100, TA1535, TA1538) were utilized for this purpose. Dose‐response effects producing a two‐fold increase of revertants over spontaneous levels were not observed with either S9 preparation indicating that the amino acid conjugates are not promutagens in these assays.     

Genotoxic effect of copper on salivary gland polytene chromosomes of Chironomus riparius Meigen 1804 (Diptera, Chironomidae)

The genotoxic action of copper (Cu) on the polytene chromosomes of Chironomus riparius was investigated by analysing structural and functional chromosome aberrations of fourth instars larvae hatched from eggs subject to acute (48 h) exposure with three environmentally relevant concentrations of aqueous Cu (0.005, 0.01, 0.05 mg/l). A dose dependent relationship was observed between Cu concentration and frequency of chromosomal aberrations. A significantly higher frequency of functional alterations, specifically decondensed centromeres and telomeres, and reduction in activity of Balbiani rings, was observed in treated material compared to control. A comparison of breakpoints resulting from treatment with chromium and lead from earlier studies with those Cu-induced identified a series of chromosomal weak points particularly vulnerable to trace metals. We also show that the appearance of structural and functional chromosome aberrations are more sensitive indicators of acute Cu toxicity in chironomid larvae than changes in external morphology.     

Mutagenicity of ambient air pollutants collected near aluminum industries

Mutagenicity has been tested in air samples collected in the summer and in the winter near four Norwegian aluminum plants. The samples were separated into a particulate and a volatile fraction and tested for mutagenicity by a quantitative reversion assay which showed that the suspended particles were clearly mutagenic. The volatile part of the air pollutants were cytotoxic to the bacteria and showed only marginal mutagenicity. The particulate fractions were tested more extensively in the Ames Salmonella mutagenicity test, in two laboratories, using the strains TA 98 and TA 100 with and without enzymatic activation (S9). The mutagenicity was relatively high compared to particulate fractions from other areas with industry and dense traffic. The highest mutagenicity was found in TA 100 with enzymatic activation and the lowest in TA 100 without S9. The mutagenicity was influenced by wind speed and direction during sampling. The mutagenic activity was also determined in the nitroreductase deficient strains TA 98NR and TA 98/1.8DNP. A larger reduction in the activity was found compared to samples from other areas, thus indicating a difference in the sample composition.     

Effect of carbaryl (carbamate insecticide) on acetylcholinesterase activity of two strains of Daphnia magna (Crustacea,Cladocera)

The present study was designed to investigate the effect of carbaryl (carbamate insecticide) on the acetylcholinesterase activity in two strains (same clone A) of the crustacean cladoceran Daphnia magna. Four carbaryl concentrations (0.4, 0.9, 1.8 and 3.7 µg L^?1) were compared against control AChE activity. Our results showed that after 48 h of carbaryl exposure, all treatments induced a significant decrease of AChE activities whatever the two considered strains. However, different responses were registered in terms of lowest observed effect concentrations (LOEC: 0.4 µg L^?1 for strain 1 and 0.9 µg L^?1 for strains 2) revealing differences in sensitivity among the two tested strains of D. magna. These results suggest that after carbaryl exposure, the AChE activity responses can be also used as a biomarker of susceptibility. Moreover, our results show that strain1 is less sensitive than strain 2 in terms of IC50-48 h of AChE activity. Comparing the EC50-48 h of standard ecotoxicity test and IC50-48 h of AChE inhibition, there is the same order of sensitivity with both strains.     

Mutagenicity evaluation of industrial sludge from common effluent treatment plant

Sludge from common effluent treatment plant (CETP) receiving effluents from textile industries at Mandia Road, Pali, was analyzed to assess the level of mutagenicity. Mutagenicity assay using Salmonella typhimurium tester strains TA 98 and TA 100 gave positive results, thus suggesting presence of genotoxic contaminants in the samples investigated. Further, mutagenic activity of chemical sludge was found to be lesser than that of biological sludge. This result is very surprising and unexpected as it is indicating that some mutagenic compounds are either being formed or certain promutagenic compounds are being converted into stable mutagenic metabolites during the biological treatment of the wastewater effluents. There have been no previous reports giving similar or contrary results. Most of the previous studies have reported effects of single combined sludge.     

Urban airborne particulate: genotoxicity evaluation of different size fractions by mutagenesis tests on microorganisms and comet assay

The genotoxic effects of different size fractions of airborne particulate (Total, PM₁₀ and PM_2.5), extracted with acetone or toluene, were evaluated by: the Ames plate test (TA98 and TA100 strains, w/o S9), gene conversion and reversion (w/o endogenous metabolic activation) in the Saccharomyces cerevisiae D7 strain, and the comet assay on human leukocytes. The data on human leukocytes confirm the sensitivity of the comet assay and its applicability to assess genotoxicity in environmental samples. The PM_2.5 fraction of airborne particulate generally shows the highest concentration of DNA-damaging compounds. Genotoxic response, in all the test systems applied, is highly dependent on extraction solvent used. Acetone seems to extract compounds with more similar genotoxic responses in the three test systems used than toluene extracts. Toluene appears to extract air pollutants genotoxic on yeast and leukocytes but is mainly cytotoxic on Salmonella.     

Cytogenetic changes in subjects occupationally exposed to benzene

Humans are exposed to benzene from various occupational and environmental sources. The genotoxic effects of benzene were assessed in peripheral blood lymphocytes of 36 workers employed in the shoe industry for a period extending from seven months to over 30 years. Chromosomal aberrations and sister chromatide exchanges were used as indicators of genotoxic effects. The incidence of dicentric chromosomes in the exposed group was significantly higher than in the control group (P < 0.05). No significant increase was detected between the working period in the exposed group and chromosomal aberrations. Sister chromatide exchange (SCE) frequency was not significantly increased in the exposed group.     

Chemical and biological profiles of sediments as indicators of sources of contamination in Hamilton Harbour. Part II: bioassay-directed fractionation using the Ames Salmonella/microsome assay

Bottom sediment and suspended sediment samples from Hamilton Harbour (western Lake Ontario) and from a major tributary were profiled using a bioassay-directed fractionation approach. Sample extracts were fractionated using an alumina/Sephadex gel clean-up procedure to afford non-polar aromatic fractions which were characterized using chemical analyses and the Ames/microsome bacterial assay in Salmonella typhimurium strains YG1025 with the addition of oxidative metabolism (S9), and YG1024 without S9. Non-polar aromatic fractions of selected samples were separated by normal phase HPLC into 1-min fractions which were subjected to bioassay analyses. The bioassays using strain YG1025+S9, a TA100-type strain, were performed to assess genotoxicity arising from the presence of polycyclic aromatic hydrocarbons (PAH). Fractions which exhibited mutagenic activity contained PAH with molecular masses of 252, 276 and 278 amu; these fractions contained over 80% of the genotoxicity attributable to PAH. Individual compounds identified using Gas Chromatography-Mass Spectrometry analyses in these active fractions included benzo[a]pyrene, indeno[cd]pyrene and dibenz[a,h]anthracene. The YG1025+S9 mutagenic activity profiles were similar for all samples. Mutagenic activity profiles generated using strain YG1024-S9, a TA98-type strain sensitive to compounds characteristic of mobile source emissions, were very different. The mutagenic activities in strain YG1024-S9 were greatest for harbour-suspended sediment samples collected from sites impacted by a major tributary. Suspended sediments collected near areas known to contain high levels of coal tar-contamination in the bottom sediments contained higher levels of genotoxic PAH than suspended sediments collected from other areas of the harbour.     

Effect of a base-catalyzed dechlorination process on the genotoxicity of PCB-contaminated soil

We evaluated the genotoxicity of dichloromethane (DCM) extracts of PCB-contaminated soil before and after the soil had been treated by a base-catalyzed dechlorination process. The treatment process involves heating a mixture of the soil, polyethylene glycol (or hydrocarbons with boiling points of 310–387°C), and sodium hydroxide to 250–350°C. Dechlorination reduced by >99% the PCB concentration of the soil, which was initially 2,200 ppm. The DCM extracts of both control and treated soils were not mutagenic in strain TA100 of Salmonella, but they were mutagenic in strain TA98. Based on results in strain TA98, the base-catalyzed dechlorination process reduced the mutagenic potency of the soil by approximately one-half. The DCM extracts of the soils before and after treatment were equally genotoxic in a prophage-induction assay in . , which detects some chlorinated organic carcinogens that are not detected by the Salmonella mutagenicity assay. These results suggest that treatment of PCB-contaminated soil by base-catalyzed dechlorination reduced the mutagenicity of the soil slightly.