Worker study finds evidence for cancer risk from atrazine

Regulators often rely on occupational health studies on the assumption that higher than average exposures experienced by agrochemical factory workers can provide early warnings of harmful effects. A long-term study of atrazine(1), one of the most widely used herbicides in the world, indicates just such a hazard, but its findings are disputed by manufacturers Syngenta.

A fourteen-year study, funded by the company, at its St Gabriel plant in Louisiana, US, has been conducted by epidemiologists at the University of Alabama. A statistical analysis of the health of more than 2,000 employees has shown a higher than expected rate of prostate cancer in the plant. Among 531 active employees, for example, the study found an incidence of cancer in 11 people, more than six times the rate that would be expected among the population in the industrial corridor between New Orleans, and Baton Rouge, and almost ten times the state average. Four employees with prostate cancer have initiated legal proceedings against Syngenta.
    Overall the study showed a statistically significant cancer risk only for prostate cancer, though cancer rates for the throat, oesophagus, stomach, bladder, thyroid, lymphatic and blood were slightly elevated compared to the state and industrial corridor.
Syngenta has refuted these findings on the basis of reports from four epidemiologists commissioned to review the statistical analysis. These reports concluded that the rises can be accounted for by a more rigorous test – prostate-specific antigen testing – introduced in the early 1990s. 
    A common weakness in epidemiological studies on pesticide-related ill-health is that precise exposure data, often inaccessible, can be missing: this study includes no detailed work patterns or exposure histories of the workers. However, Baton Rouge lawyer J Chandler Loupe, representing the workers, said that in the 1970s and early 1980s, employees were routinely exposed to atrazine dust in the factory. ‘They would go into the packaging area and come out covered in white powder’, says Loupe. ‘They were told that exposure is not an issue. Supervisors said ‘You can eat it.’’
    The potential for human carcinogenicity of atrazine has long been in dispute(2). In December 2000(3), the US Environmental Protection Agency (EPA) re-classified the human carcinogenic potential of atrazine from ‘Likely’ to ‘Not likely’, based on studies showing that carcinogenic effects were only found in one strain of rat. The St Gabriel study casts new doubt on this conclusion.
There is continuing disquiet about atrazine. New studies(4) have shown that atrazine causes feminising effects on leopard frogs at levels as low as 0.1 parts per billion.
    In its January interim review, the EPA has imposed tough new restrictions on the pesticide to prevent contamination of drinking water. The EPA’s review of atrazine, to include its effects on amphibia, will be completed by October 2003. (AC)

References
1. Delzell, E, Sathiakumar N, MacLennan P, Grizzle W, Cheng H, A follow-up study of cancer incidence among workers in triazine-related operations at the Novartis St. Gabriel plant [unpublished] Times-Picayune article, Factory cancer study fuels worries, 26 January 2003, John McQuaid www.timespicayune.com
2. PN 56, fact sheet on atrazine, page 20.
3.United States Environmental Protection Agency, Health Effects Division document number 014431, 13th December 2000, www.epa.gov/oppsrrd1/reregistration/atrazine/carc-rpt.pdf
4. PN 58, page 19.

[This article first appeared in Pesticides News No. 59, March 2003, page 21]