NEWS
SCIENCE Atrazine found to cause chromosomal breaks 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."
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.
Several studies have detected atrazine in surface water and groundwater. According to R. Peter Richards of Heidelberg College's Water Quality Laboratory, atrazine concentrations reach MCL levels for only short periods of time, typically in smaller watersheds such as streams or rivers following rainfall and seasonal applications. However, Richards, who has studied atrazine exposure in the Midwest, said it is quite common for atrazine levels in those situations to be as high
as 10 ppb. Rayburn's group found the chromosome breaks after exposing Chinese hamster ovary cells to low levels of atrazine. The chromosomes were isolated and individually separated by flow cytometry. No chromosomal breaks were observed with the related triazine herbicide simazine or with the thiodiazine herbicide bentazone. The research will be published in the Journal of Environmental Quality in December. —ALAN NEWMAN
Do microbes contribute to sick building syndrome? Could volatile organic compounds (VOCs) emitted from molds and fungi be a significant source of indoor air pollution in some buildings? Investigations in the southeastern United States have uncovered a number of "sick" buildings in which microbes seem to be the major source of ambient VOCs, according to Charlene Bayer, director of Georgia Institute of Technology's Indoor Environment Research Program. Of particular significance, said Bayer, was the discovery that the sick building microbes emitted solvent-type VOCs such as ben-
zene, hexane, and acetone. Typically, high indoor levels of these VOCs are blamed on cleaning materials, paints, and new carpet. "Because the VOCs have usually been attributed to these other types of sources, the source control may be incorrect," said Bayer. Other indoor air researchers remain skeptical that the microbes are major sources. "There is not much in the way of numbers," said loan Daisey of the Lawrence Berkeley Laboratory, referring to the lack of mass balance analyses. "Unless the emission rates from the microbes are pretty high, you wouldn't expect
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to see a buildup of VOCs." Bayer said her group identified sick buildings where the primarily VOC sources that could be found were molds and fungi. In one "very moldy" building her group measured ambient hexane levels as high as 11,000 ppm, but could find no source other than the microbes. Samples collected in sick buildings by Bayer's group were cultured in the laboratory, and metabolic emissions were analyzed for VOCs. Among the sick building microbes found were Cladosporium, Pénicillium, and Aspergillus. —ALAN NEWMAN
