Response from Syngenta: The need for objective, science-based advocacy Recent exchanges on the appropriate role of science-based advocacy have considered the case of the herbicide atrazine, registered by Syngenta. Dr. Hayes campaigns for banning atrazine despite international regulators’ and independent experts’ conclusions that atrazine is not likely carcinogenic in humans and does not affect amphibians. Hayes’ response (1) disregards data counter to his advocacy goals and such biased advocacy undermines the credibility of the scientific process, potentially resulting in misguided policy decisions. Hayes cites Carr (2), to advocate that atrazine causes feminization and intersex in developing male amphibians. Actually, Carr et al. state, “animals classified as intersex in the 25 µg atrazine/L treatment group [based on gross pathology] tended to have an obvious testicular or ovarian morphology.. .” (2). “Intersex” gonads were initially classified based on ambiguous gross morphological appearance but, histological evaluation produced no evidence of hermaphrodites. This lack of hermaphroditism was subsequently and independently confirmed (3). Hayes also cites Orton (4) to support his position, however in this study control mortalities were high (50%) compared to atrazine (15%) or nitrate (10%) and significant increases in the frequency of both males and females is reported. When combined, atrazine/nitrate exposure resulted in increased females only. The occurrence of intersex frogs is highest in the controls and not significantly different. These results do not support the Hayes position. Objective science-based advocacy should consider valid data, even if they do not support one’s desired advocacy goals. Five recent studies have failed to support Hayes’ findings of low-level (g0.1 µg/L) atrazine 10.1021/es902241t
effects on gonadal development (5-8). The USEPA required that Syngenta conduct further investigations, and two experiments (U.S. and Germany) were conducted under the complete transparency of Good Laboratory Practices, and USEPA and German regulatory inspection. No impact of atrazine (0.01-100 µg/L) on metamorphosis or gonadal development was detected (5). The USEPA concluded “that atrazine does not adversely affect amphibian gonadal development” (9). A panel of independent expert scientists convened by the USEPA agreed that “reproductive fitness (sex ratio, intersex condition) were unaffected” and “there is currently no available proof for the hypothesis regarding the purported action of atrazine on the induction of aromatase” (10). Oka et al. (6) exposed X. laevis larvae to atrazine and while a difference in sex ratios was reported at 10 and 100 µg/L, the authors concluded that “higher female ratios in atrazine exposure groups in the present study were not caused by estrogenic action of atrazine.” LaFiandra et al. (7) exposed North American treefrogs (Hyla verisicolor) to 20 and 200 µg/L atrazine and reported no effects on sex ratio or gonadal development. Likewise, Storrs and Semlitsch (8) exposed three North American species (Bufo americanus, Hyla versicolor, and Rana sphenocephala) to atrazine (1, 3, or 30 µg/L) and reported no effects on metamorphosis or ovarian development. Hayes’ campaign against atrazine illustrates that the need for good science in science-based advocacy is not, as stated, a “gratuitous statement of the obvious” (11). ALAN J. HOSMER* Syngenta Crop Protection, Inc.
[email protected] (1) Hayes, T. More feedback on whether atrazine is a potent endocrine disruptor chemical. Environ. Sci. Technol. 2009, 43, 10.1021/ es901511h.
2009 American Chemical Society
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(2) Carr, J. A.; Gentles, A.; Smith, E. E.; Goleman, W. L.; Urquidi, L. J.; Thuett, K.; Kendall, R. J.; Giesy, J. P.; Gross, T. S.; Solomon, K. R.; Van Der Kraak, G. J. Response of larval Xenopus laevis to atrazine: assessment of gonadal and laryngeal morphology. Environ. Toxicol. Chem. 2003, 22, 396–405. (3) 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. (4) Orton, F.; Carr, J. A.; Handy, R. D. Effects of nitrates and atrazine on larval development and sexual differentiation in the northern leopard frog Rana pipiens. J. Environ. Toxicol. Chem. 2006, 25 (1), 65–71. (5) Kloas, W.; Lutz, I.; Springer, T.; Krueger, H.; Wolf, J.; Holden, L.; Hosmer, A. Does Atrazine Induce Gonadal Feminization in Xenopus laevis?. Toxicol. Sci. 2009, 107 (2), 376–384. (6) Oka, T.; Tooi, O.; Mitsui, N.; Miyahara, M.; Ohnishi, Y.; Takase, M.; Kashiwagi, A.; Santo, N.; Iguchi, T. Effect of atrazine on metamorphosis and sexual differentiation in Xenopus laevis. Aquat. Toxicol 2008, 87, 215–226. (7) LaFiandra, E. M.; Babbitt, K. J.; Sower, S. A. Effects of atrazine on anuran development are altered by the presence of a nonlethal predator. J. Toxicol. Environ. Health, Part A 2008, 71, 505–511. (8) Storrs, S. I.; Semlitsch, R. D. Variation in somatic and ovarian development: Predicting susceptibility of amphibians to estrogenic contaminants. Gen. Comp. Endrocrinol. 2008, 156, 524–530. (9) USEPA. White Paper on the Potential for Atrazine to Affect Amphibian Gonadal Development; Submitted to the FIFRA Scientific Advisory Panel for Review and Comment; October 9-12, 2007. (10) FIFRA SAP Report No 2007-08; FIFRA Scientific Advisory Panel Meeting, October 9-11, 2007 Arlington VA; A Set of Scientific Issues Being Considered by the Environmental Protection Agency Regarding: The Potential for Atrazine to Affect Amphibian Gonadal Development; 2007. (11) Collins, T. J. Response from Collins. Environ. Sci. Technol. 2008, 43 (9), 2994. Environmental Science & Technology edits all Letters for length, punctuation, and clarification of references. Authors approve of changes prior to publication.
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