| Abstract: | Chlorinated organics represent an important class of environmental carcinogens. However, only a small percentage of the carcinogens of this chemical class are genotoxic in prokaryotic bioassays such as the Salmonella assay. In an effort to identify a short-term assay sensitive to chlorinated carcinogens, we have tested a group of chlorinated pesticides, most of which are carcinogenic in rodents, in a prophage-induction assay developed by Rossman et al. (1984). The Microscreen phage-induction assay is a rapid, inexpensive, miniaturized system that uses the induction of prophage lambda in Escherichia coli as an indicator of genetic damage. It has been used successfully to screen complex environmental samples for genotoxicants and has detected carcinogenic metals that are refractory in the Salmonella assay. The pesticides tested were malathion, monuron, p,p'-DDT, mirex, lindane, nitrofen, chlordane, toxaphene, captan, and dichlorvos. All but the first 4 induced prophage. The remaining pesticides were ranked as follows according to induction potency in the presence of S9: captan greater than dichlorvos greater than toxaphene greater than lindane greater than nitrofen greater than chlordane. Rankings were similar in the absence of S9. Of these 6 pesticides, only nitrofen required S9 to induce prophage. Comparisons with mutagenesis data in Salmonella indicated that the Microscreen assay detected as genotoxic each of the pesticides that were mutagenic in Salmonella; moreover, it detected 2 additional carcinogens (chlordane and lindane) that were not mutagenic in the Salmonella assay. The possible use of the Microscreen phage-induction assay to detect chlorinated organics is discussed. |
