More bad news for triazine herbicides EPA announced in August that DuPont Agricultural Products, sole manufacturer of the triazine herbicide cyanazine, will voluntarily phase out production over the next four years. An estimated 36 million lb of cyanazine are used annually, primarily on corn crops. After July 25,1996, the herbicide's label will recommend reduced maximum seasonal application rates. Sales and distribution of cyanazine will be prohibited after December 31,1999. According to Jack Housenger, chief of the Special Review Branch in the Office of Pesticide Programs (OPP), DuPont approached EPA about the phaseout. In November of last year, OPP initiated a special review of cyanazine as well as atrazine and simazine. "DuPont didn't want to go through a special review and live with the restrictions," said Housenger. Alternatives to cyanazine are now or soon will be available, added Housenger, particularly the new sulfonyl urea herbicides. Penelope Fenner-Crisp, acting deputy director of OPP, cited the discovery that triazine herbicides could cause mammary tumors in one strain of rats as well as research that suggests that chlorotriazines are endocrine disrupters as the triggers for the special review. According to Fenner-Crisp, OPP expects to present for comment a peer-reviewed, integrated hazard assessment of triazines covering human health issues in the first half of 1996. Hamster cells exposed for 48 h to the herbicide atrazine at EPA's maximum contaminant level (MCL) for drinking water of 3 ppb have been found to develop chromosomal breaks. Similar breaks in human chromosomes have been linked to certain cancers and birth defects. These results are the first to tie short-term exposures of low-level atrazine to chromosomal damage, according to the study's lead researcher, A. Lane Rayburn of the University of Illinois Agronomy Department. Thus, said Rayburn, the study may more closely mimic human exposure than do studies in which rats are fed high dosages to test for tumors. Atrazine ranks as one of the most widely used pesticides in the United States; according to EPA, as much as 80 million pounds are dispersed annually. On the basis of animal studies, EPA lists atrazine as a possible human carcinogen and is currently reviewing its status (see sidebar). Rayburn cautioned that the atrazine results do not yet translate to an increased human health risk. The chromosome breaks could be fixed by DNA repair enzymes, for example, he said. "We need to proceed to the next step, the testing of human tissues."