Tyrone Hayes

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Tyrone Hayes
Tyrone Hayes at King University in 2013 (10680719164).jpg
Hayes at King University in 2013
Born (1967-07-29) July 29, 1967 (age 53)
EducationPhD (1993, Berkeley), BA (1989, Harvard)

Tyrone B. Hayes (born July 29, 1967) is an American biologist and professor of Integrative Biology at University of California, Berkeley known for his research concluding that the herbicide atrazine is an endocrine disruptor that demasculinizes and feminizes male frogs. He is also an advocate for critical review and regulation of pesticides and other chemicals that may cause adverse health effects. He has presented hundreds of papers, talks, and seminars on his conclusions that environmental chemical contaminants have played a role in global amphibian declines and in the health disparities that occur in minority and low income populations.

Hayes' research into atrazine as an endocrine disruptor has not been able to be replicated[1][2] and has been contested by Syngenta (the manufacturer of atrazine) and the Australian Pesticides and Veterinary Medicines Authority. The Environmental Protection Agency (EPA) and its independent Scientific Advisory Panel examined all available studies and concluded that "atrazine does not adversely affect amphibian gonadal development based on a review of laboratory and field studies."[3] Hayes' research was used as the basis for the settlement of a multimillion-dollar class-action lawsuit against Syngenta.

Early life and education[edit]

Tyrone Hayes was born in Columbia, South Carolina to Romeo and Susie Hayes in 1967. As a child he studied lizards and frogs, particularly interested in the way that frogs morphed from tadpoles to their adult form. He won a state science fair with research that showed anole lizards had to be awake to change color.[4] He graduated from Dreher High School in 1985 and earned B.A. and M.A. degrees in biology in 1989 from Harvard University. His dissertation was on the genetic and environmental mechanisms determining the gender of the wood frog. He continued his studies at the University of California, Berkeley, where he received his Ph.D. degree in integrative biology in 1993 for his study of the role of hormones in mediating developmental responses to environmental changes in amphibians.[5]


After graduating from Harvard University, Hayes worked as a technician and freelance consultant from 1990–1992 for Tiburon, California-based Biosystems, Inc.[6] Hayes has held an academic appointment (professorship) at the University of California, Berkeley since completing his doctoral research there in 1992;[4] he was hired as a graduate student instructor in 1992, became an assistant professor in 1994, associate professor in 2000, and professor in 2003 in the Department of Integrative Biology, Molecular Toxicology, Group in Endocrinology, Museum of Vertebrate Zoology, Energy and Resources Group, University of California, Berkeley.[6]

Hayes’ scientific research has focused on the potential of genetic adaptation and the role of hormones in the development of the amphibian. His investigations have shown that chemical agents, such as a commonly used herbicide, have the ability to negatively impact the sexual development of the amphibian, even when such toxins are present in low concentrations. Hayes has taken an interest in the hormonal regulation and development of aggressive behavior. He has also been active with the National Science Foundation Review Panel since 1995, and he has served on several other advisory boards as well.

Atrazine research[edit]

Xenopus laevis, the African Clawed frog

In 1997, the consulting firm EcoRisk, Inc. paid Hayes to join a panel of experts conducting studies for the Swiss pharmaceutical company Novartis (later Syngenta) on the herbicide atrazine.[4][7] When Hayes' research found unexpected toxicities for atrazine, he reported them to the panel, however the panel and company were resistant to his findings. He wanted to repeat his work to validate it but Novartis refused funding for further research; he resigned from the panel and obtained other funding to repeat the experiments.[4][7]

In 2002 Hayes published findings that he says replicate what he found while he was working for EcoRisk,[4] that developing male African clawed frogs and leopard frogs exhibited female characteristics after exposure to atrazine, first in the Proceedings of the National Academy of Sciences (PNAS)[8] and then in Nature.[9][10]

In 2007, Hayes was a co-author on a paper that detailed atrazine inducing mammary and prostate cancer in laboratory rodents and highlighted atrazine as a potential cause of reproductive cancers in humans.[11] In 2007, Hayes presented results of his studies to the U.S. National Institute of Environmental Health Sciences showing chemical castration in frogs; individuals of both sexes had developed bisexual reproductive organs.[12] In 2010, Hayes published research in PNAS[13] describing laboratory work showing how exposure to atrazine turned male tadpoles into females with impaired fertility.[7]

The U.S. Environmental Protection Agency (EPA) and its independent Scientific Advisory Panel (SAP) examined all available studies on this topic and concluded that "atrazine does not adversely affect amphibian gonadal development based on a review of laboratory and field studies.".[14] The EPA and its SAP made recommendations concerning proper study design needed for further investigation into this issue. As required by the EPA, Syngenta conducted two experiments under Good Laboratory Practices (GLP) and inspection by the EPA and German regulatory authorities. The paper concluded "These studies demonstrate that long-term exposure of larval X. laevis to atrazine at concentrations ranging from 0.01 to 100 microg/l does not affect growth, larval development, or sexual differentiation."[15] A report written in Environmental Science and Technology (May 15, 2008) cites the independent work of researchers in Japan, who were unable to replicate Hayes' work. "The scientists found no hermaphrodite frogs; no increase in aromatase as measured by aromatase mRNA induction; and no increase in vitellogenin, another marker of feminization."[16] In 2010, the Australian Pesticides and Veterinary Medicines Authority (APVMA) responded to Hayes' 2010 published paper,[17] by stating that his findings "do not provide sufficient evidence to justify a reconsideration of current regulations which are based on a very extensive dataset."[3]


A map of pounds per square mile of atrazine application in the U.S. in 1997

Since publishing his research on atrazine as an endocrine disruptor, Hayes has become an advocate for banning atrazine.[18] According to Hayes, the link between atrazine and altered "aromatase and estrogen production has been demonstrated... in fish, frogs, alligators, birds, turtles, rats and human cells", and, "I believe that the preponderance of the evidence shows atrazine to be a risk to wildlife and humans. I would not want to be exposed to it, nor do I think it should be released into the environment."[18][19] He travels and lectures extensively to both scientific and lay audiences, almost never declining an invitation.[7]

He also has raised issues of environmental racism, warning that "if you’re black or Hispanic, you’re more likely to live or work in areas where you’re exposed to crap".[7] While a biologist on the Public Broadcasting Service, National Geographic program Strange Days, he expressed his concerns for human health, particularly that of minority and low-paid workers exposure to agricultural chemicals.[20]

Research published by Hayes and other scientists was used as evidence in a class action lawsuit against Syngenta by 15 water providers in Illinois that was settled for 105 million dollars in May 2012,[10][21][22] which reimbursed more than 1,000 water systems for the costs of filtering atrazine from drinking water, although the company denies any wrongdoing.[7][23]

Conflict with atrazine manufacturer Syngenta[edit]

A long running conflict between Hayes and agricultural chemical manufacturer Syngenta was described as "one of the weirdest feuds in the history of science,” by Dashka Slater in her 2012 profile of Hayes in Mother Jones magazine.[4]

In 2014, New Yorker writer Rachel Aviv reported that Syngenta might have been orchestrating an attack not only on Hayes' scientific credibility, but on other scientists as well whose studies have shown atrazine to have adverse effects on the environment and/or human and animal health.[7]

Aviv reported that Syngenta had criticized Hayes' science and conduct in press releases, letters to the editor, and through a formal ethics complaint filed at University of California-Berkeley.[7] Internal Syngenta documents from 2005 released by a class-action lawsuit in 2014 show ways that Syngenta conspired to discredit Hayes, including attempting to get journals to retract his work, and investigating his funding and private life.[7][24][25] In one of the 2005 e-mails obtained by class-action lawsuit plaintiffs, the company's communications consultants had written about plans to track Hayes' speaking engagements and prepare audiences with Syngenta's counterpoints to Hayes's message on atrazine. Syngenta subsequently stated that many of the documents unsealed in the lawsuits refer to "ideas that were never implemented."[7]

In 2010 Syngenta forwarded an ethics complaint to the University of California Berkeley, complaining that Hayes had been sending sexually explicit and harassing e-mails to Syngenta scientists, including quoting the rapper DMX.[26] Some of these emails were obtained and published by Gawker.[27] Legal counsel from the university responded that Hayes had acknowledged sending letters having "unprofessional and offensive" content, and that he had agreed not to use similar language in future communications.[26][28]

Filmography and other work[edit]

Hayes' work was featured in the 2008 documentary film Flow: For Love of Water.[29] He appeared in the 2012 documentary film Last Call at the Oasis.[30][31]

Hayes is the subject of The Frog Scientist, a biographical book for children, first published in 2009.[32]

Personal life[edit]

Hayes lives in California with his wife, Kathy Kim, and their two children, Tyler and Kassina. He has won several awards for his teaching and his research, including the Distinguished Teaching Award from University of California, Berkeley in 2002 and the President’s Citation Award from the American Institute of Biological Science in 2004. He was also awarded the National Geographic Emerging Explorer Award and the Jennifer Altman Award in 2005.[33]

See also[edit]


  1. ^ Statement of Anne E. Lindsay, Deputy Director, Office of Pesticide Programs, U. S. Environmental Protection Agency, before the Agriculture and Rural Development Committee of the Minnesota House of Representatives February 16, 2005
  2. ^ Kloas, Werner; Lutz, Ilka; Springer, Timothy; Krueger, Henry; Wolf, Jeff; Holden, Larry; Hosmer, Alan (February 2009). "Does atrazine influence larval development and sexual differentiation in Xenopus laevis?". Toxicological Sciences. 107 (2): 376–384. doi:10.1093/toxsci/kfn232. ISSN 1096-0929. PMC 2639758. PMID 19008211.
  3. ^ a b "Chemicals in the News: Atrazine". Australian Pesticides and Veterinary Medicines Authority. April 5, 2011. Archived from the original on February 24, 2014. Retrieved June 9, 2020.
  4. ^ a b c d e f Slater, Dashka (January–February 2012). "The Frog of War". Mother Jones.
  5. ^ "Biography". The History Makers. Retrieved September 24, 2020.
  6. ^ a b "Tyrone Hayes Curriculum Vita". Atrazine Lovers Website. Retrieved August 23, 2013.
  7. ^ a b c d e f g h i j Aviv, Rachel (February 10, 2014). "A Valuable Reputation: After Tyrone Hayes said that a chemical was harmful, its maker pursued him". The New Yorker. Retrieved February 7, 2014.
  8. ^ Hayes TB, Collins A, Lee M, et al. (April 2002). "Hermaphroditic, demasculinized frogs after exposure to the herbicide atrazine at low ecologically relevant doses". Proc. Natl. Acad. Sci. U.S.A. 99 (8): 5476–80. Bibcode:2002PNAS...99.5476H. doi:10.1073/pnas.082121499. PMC 122794. PMID 11960004.
  9. ^ Hayes T, Haston K, Tsui M, Hoang A, Haeffele C, Vonk A (October 2002). "Herbicides: feminization of male frogs in the wild". Nature. 419 (6910): 895–6. Bibcode:2002Natur.419..895H. doi:10.1038/419895a. PMID 12410298.
  10. ^ a b Dalton R (August 2010). "E-mails spark ethics row". Nature. 466 (7309): 913. doi:10.1038/466913a. PMID 20725013.
  11. ^ Fan, W.; T. Yanase; H. Morinaga; S. Gondo; T. Okabe; M. Nomura; T. Komatsu; K.I. Morohashi; T.B. Hayes (2007). "Atrazine-Induced Aromatase Expression is SF-1 Dependent: Implications for Endocrine Disruption in Wildlife and Reproductive Cancers in Humans". Environmental Health Perspectives. 115 (5): 720–7. doi:10.1289/ehp.9758. PMC 1867956. PMID 17520059.
  12. ^ Ball, Eddy (April 2007). "Amphibian Specialist Challenges EPA and Pesticide Manufacturers". Environmental Factor NIEHS News. National Institute of Environmental Health Sciences. Retrieved February 7, 2014. I could take tap water that is regulated by the U.S. EPA," Hayes noted, "and I could chemically castrate frogs.
  13. ^ Hayes TB, Khoury V, Narayan A, et al. (March 2010). "Atrazine induces complete feminization and chemical castration in male African clawed frogs (Xenopus laevis)". Proc. Natl. Acad. Sci. U.S.A. 107 (10): 4612–7. Bibcode:2010PNAS..107.4612H. doi:10.1073/pnas.0909519107. PMC 2842049. PMID 20194757.
  14. ^ Atrazine Updates: Amphibians, April 2010, EPA.
  15. ^ Kloas, W; Lutz, I; Springer, T; Krueger, H; Wolf, J; Holden, L; Hosmer, A (2009). "Does atrazine influence larval development and sexual differentiation in Xenopus laevis?". Toxicological Sciences. 107 (2): 376–84. doi:10.1093/toxsci/kfn232. PMC 2639758. PMID 19008211.
  16. ^ Renner, Rebecca (May 2008). "Atrazine Effects in Xenopus Aren't Reproducible (Perspective)" (PDF). Environmental Science & Technology. 42 (10): 3491–3493. Bibcode:2008EnST...42.3491R. doi:10.1021/es087113j. PMID 18546678.
  17. ^ Hayes, TB; Khoury, V; Narayan, A; Nazir, M; Park, A; Brown, T; Adame, L; Chan, E; et al. (2010). "Atrazine induces complete feminization and chemical castration in male African clawed frogs (Xenopus laevis)". Proceedings of the National Academy of Sciences of the United States of America. 107 (10): 4612–7. Bibcode:2010PNAS..107.4612H. doi:10.1073/pnas.0909519107. PMC 2842049. PMID 20194757.
  18. ^ a b "Hormone Disruptors Linked To Genital Changes and Sexual Preference", Living on Earth, National Public Radio, January 7, 2011, retrieved February 7, 2014
  19. ^ Randall Amster (March 19, 2010). "Silent Spring Has Sprung". Truthout. Retrieved February 7, 2014.
  20. ^ "Tyrone Hayes, PhD". Strange Days, Biographies. Public Broadcasting System. 2013. Retrieved August 23, 2013. I am concerned about the adverse impacts of Atrazine on endangered species and on racial/ethnic minorities. Prostate and breast cancer are two of the top causes of death in Americans age 25-40, but in particular Black and Hispanic Americans are several times more likely to die from these diseases. Ethnic minorities and people of low income are also more likely to hold the "unskilled" laborer positions in agriculture and pesticide production that would put them at higher risk of exposure and are least likely to have access to the emerging science demonstrating the dangers of exposure. Thus, this environmental and public health issue is also a racial/social justice issue because minority and working class people are the primary targets of pesticide exposure.
  21. ^ "City of Greenville v. Syngenta Crop Protection, Inc., and Syngenta AG Case No. 3:10-cv-00188-JPG-PMF". City of Greenville. Retrieved August 23, 2013.
  22. ^ Staff (June 19, 2013). "Tillery planning to file new litigation involving atrazine". Madison County Record. Retrieved August 23, 2013.
  23. ^ Berry, Ian (May 25, 2012). "Syngenta Settles Weedkiller Lawsuit". The Wall Street Journal. Retrieved February 9, 2014.
  24. ^ "Court-released documents: Exhibit 19, part1" (PDF). Source Watch. Center for Media and Democracy. Retrieved February 7, 2014.
  25. ^ Howard, Clare (June 17, 2013). "Special Report: Syngenta's campaign to protect atrazine, discredit critics". Environmental Health News. Retrieved August 23, 2013.
  26. ^ a b Dalton, Rex (August 18, 2010). "E-mails spark ethics row". Nature. 466 (7309): 913–913. doi:10.1038/466913a. ISSN 0028-0836. PMID 20725013.
  27. ^ Nolan, Hamilton. "Dr. Tyrone Hayes: Biologist, Cock-Fixated Megalomaniac Email Addict". Gawker. Retrieved June 9, 2020.
  28. ^ "Ethics complaint from Syngenta" (PDF).
  29. ^ Collins, Cyn (July 31, 2008). "Film note: All dried up". Twin Cities Daily Planet. Retrieved August 23, 2013.
  30. ^ "Tyrone Hayes". www.imdb.com. Retrieved June 24, 2014.
  31. ^ Scott, A.O. (May 3, 2012). "When There Really Is Not a Drop to Drink 'Last Call at the Oasis,' a Documentary About Water Supplies". New York Times. Retrieved February 7, 2014. Tyrone Hayes, a biologist, shows us mutant frogs, their endocrine systems scrambled by pesticide-borne chemicals.
  32. ^ Pamela S. Turner (2009). The Frog Scientist. Houghton Mifflin Books for Children. ISBN 978-0-618-71716-3.
  33. ^ "Biography". The History Makers. Retrieved September 24, 2020.

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