More feedback on whether atrazine is a potent endocrine disruptor chemical I read with interest the article by Terry Collins and the subsequent exchange between Keith Solomon and Collins (published May 1, 2009). I have also read the review by Solomon, Carr, Giesy, and others (1), the basis for Solomon’s letter. It is difficult to decide how to respond to a review that summarily dismisses over 100 peer reviewed publications showing adverse effects of atrazine. Perhaps the best approach is to let the authors speak for themselves. In their review (1), the authors conclude that, “With rare exceptions, the only studies that report adverse effects on amphibian development and reproduction are those from the Hayes laboratory” (1). This conclusion differs substantially from the opinion of co-author Carr, who wrote, “The important issue is for everyone involved to come to grips with and stop minimizing the fact that independent laboratories have demonstrated an effect of atrazine on gonadal differentiation in frogs. There is no denying this” (2, 3). Carr himself published an article that showed significant (P < 0.0003 and P < 0.0042) adverse effects of atrazine on gonadal development in African clawed frogs (4). He later supported this finding with studies in leopard frogs: “Overall, this study has demonstrated changes in sex ratios that are more marked in response to
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combined nitrate/atrazine exposure than with these chemicals alone.” (5). Regarding aromatase induction and estrogen production by atrazine, Solomon et al. concluded that “... this is not a mechanism by which atrazine could affect reproductive development or reproduction in amphibians and fish.” (1) This contradicts Giesy, who discovered the induction of aromatase by atrazine two years before my laboratory’s publications, claiming that “several members of the class of 2-chloro-s-triazine herbicides induce the human aromatase enzyme in vitro at relatively low concentrations” (6), and that “A logical concern would be that exposure of wildlife and humans to triazine herbicides... may similarly contribute to estrogen mediated toxicities and inappropriate sexual differentiation.” (6) Also, self-contradictory, is the fact that the former manufacturer of atrazine (Novartis) dismisses the role of atrazine’s induction of aromatase in human breast cancer, yet they have now introduced an aromatase inhibitor as a major treatment for breast cancer (7). Finally, regarding his studies of atrazine-induced aromatase, Giesy wrote, “Industry tried to block publication of both of our papers so I am leery of their mode of operation.” (3) As Solomon, Giesy et al. report that their recent review “was developed with a grant from Syngenta Crop Protection, Inc” (1), readers should heed Giesy’s warn-
2009 American Chemical Society
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ing and similarly be “leery” of the opinions of industry-sponsored scientists. TYRONE HAYES* University of California, Berkeley
[email protected] (1) Solomon, K. R.; Carr, J. A.; Du Preez, L. H.; Giesy, J. P.; Kendall, R. J.; Smith, E. E.; Van Der Kraak, G. J. Effects of Atrazine on Fish, Amphibians, and Aquatic Reptiles: A Critical Review. Crit. Rev. Toxicol. 2008, 38 (9), 721–772. (2) Hayes, T. B. There is no denying this: Defusing the confusion about atrazine. Bioscience 2004, 54 (12), 1138–1149. (3) Environmental Protection Agency. FOIA Request Identification Number HQ-RIN-0045-04; 2003. (4) Carr, J. A.; et al. Response of larval Xenopus laevis to atrazine: Assessment of growth, metamorphosis, and gonadal and laryngeal morphology. Environ. Toxicol. Chem. 2003, 22, 396–405. (5) Orton, F.; Carr, J. A.; Handy, R. D. Effects of nitrate and atrazine on larval development and sexual differentiation in the northern leopard frog Rana pipiens. J. Environ. Toxicol. Chem. 2006, 25 (1), 65–71. (6) Sanderson, J. T.; Seinen, W.; Giesy, J. P.; van den Berg, M. 2-chloro-striazine herbicides induce aromatase (CYP19) activity in H295R human adrenocortical carcinoma cells: A novel mechanism for estrogenicity? Toxicol. Sci. 2000, 54, 121– 127. (7) How Femara Works; http://www. femara.com/content/ estrogen-receptor.jsp. Environmental Science & Technology edits all Letters for length, punctuation, and clarification of references. Authors approve of changes prior to publication.
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