By Leigh Davis
Endocrine disruption was first discovered in the 1930s when researchers saw that some industrial chemicals, among them, bisphenol A, had estrogenic effects in lab animals.
In the 1950s, women with difficult pregnancies took the drug diethylstilbesterol (DES) to prevent miscarriage. DES affected the children of these women, causing daughters to develop a rare cancer called clear cell adenocarcinoma or reproductive structural differences, pregnancy complications, or fertility. Sons could have genital abnormalities or infertility.
In 1962, ecologist Rachel Carson’s groundbreaking book Silent Spring was published as a warning against the use of chemical pesticides in agriculture. Chemical companies attacked her as an “alarmist.” Pesticides have turned out to be one of the more significant sources of endocrine disruption, particularly in wildlife. Carson died of breast cancer in 1964.
In 1989, zoologist Theo Colborn published Our Stolen Future, drawing the connection between the strange deformities that had begun to show up in wildlife and exposures to human-made chemicals that had migrated into the environment. Colborn hypothesized that a class of chemicals called “endocrine disruptors” was affecting not only the wildlife, but also human endocrine systems, resulting in a wide range of health effects, and could potentially rob humans of our ability to reproduce.
Colborn’s research was criticized by apologists for chemical companies, who called her “alarmist.” In 2004, during her acceptance speech for the Rachel Carson Award for Integrity in Science, Colborn said, “Forty years ago, Rachel Carson alluded to endocrine disruptors in her book… She sounded the first warning that chemicals were violating what I call ‘inner space,’ when she pondered the consequences of mothers sharing their body burdens of synthetic chemicals with the developing babies in their wombs.”
Unlike the premise of the current apocalyptic film Children of Men, in which globally, women become infertile, Colborn identified declining sperm counts resulting from exposure to certain plastics as the likely culprit in our stolen future.
During the 1990s, University of Florida–Gainesville zoologist Louis Guillette discovered that alligators in Lake Apopka had testosterone levels low enough to make them sterile and abnormally small penises (a quarter the size of normal). The likely culprit: DDT-containing pesticides had been spilled in the lake in 1980. A metabolite of DDT is DDE, which acts like estrogen.
In 1998, University of California–Berkeley developmental endocrinology researcher Tyrone Hayes joined a group of consultants called the Atrazine Endocrine Disruption Panel to investigate the effects of the widely used agricultural herbicide atrazine on wildlife. Atrazine is manufactured by the agribusiness giant, Syngenta, who funded the research. Syngenta is a corporate entity formed by two pharmaceutical companies, Novartis and Zeneca.
Hayes, whose specialization is frogs, found that atrazine, at concentrations as low as one part per billion (1 ppb) had negative effects on larynx development in his male frogs. EPA guidelines put the safe levels of atrazine for humans at 3 ppb.
When the group he was working with refused additional funding for further study and otherwise stalled additional research, Hayes continued the work on his own, ultimately finding that atrazine had “feminizing” effects on the male frogs’ sexual organs at 0.1 ppb.
Atrazine was increasing the production of estrogen. Over six years, Hayes withstood what appeared to be attempts to discredit his research by researchers and others in the employ of Ecorisk, the company that contracted to do the research for Syngenta. Later, other research would link atrazine with prostate cancer and non-Hodgkin’s lymphoma in factory workers manufacturing the chemical.
In the United States, more than 76 million pounds of atrazine are used every year on 90 percent of sugar cane fields and two out of three cornfields and sorghum fields, as well as on golf courses, Christmas-tree farms, and lawns. Atrazine use has been banned in much of Europe.
At a June 2006 research conference in Barga, Italy, researchers from all over the world presented evidence on the human effects of endocrine disruptors, including their mechanisms of action, transgenerational effects, low-dose effects, and their relationship to obesity and metabolic syndrome (a precursor of diabetes).