Theo Colborn and Endocrine Disruption

By Jaime Seltzer

We have unwittingly and catastrophically changed the atmosphere… and the womb.” – Theo Colborn

Theo Colborn was already an unconventional learner by the time she was in high school in the 1940s, taking science classes that it was understood were meant to be for the boys. Growing up in a family that was still struggling with the aftereffects of the Great Depression, she thought there was little chance she would ever go to college, though she found science fascinating.

Just by chance, her high school guidance counselor knew someone at the registrar at Rutgers University’s College of Pharmacy. Theo did not know her name had been entered for a scholarship until her second week as a lab technician. She returned home to find that Rutgers had called, promising her a four-year scholarship so long as she kept her grades up! Theo continued to work as a lab tech part-time while she completed her degree in pharmacy. She married and worked and even retired before she, like many women of the late 1970s and early 1980s, went through a divorce. Her job was done; her marriage was over; her children were old enough to look after themselves. So Theo Colborn began a second life from scratch.

At age fifty, Theo moved to a farm that was close to the Rocky Mountain Biological Laboratory in Colorado, and volunteered to help with field research in which she was to collect insects and water samples to see if they had been contaminated by nearby mining operations.

Colborn is also almost single-handedly responsible for the banning of PCPs in the late 1970s, chlorinated organic molecules with benzene rings.

Theo became fascinated with the process of environmental analysis and what it could mean for the environment and its inhabitants, including human beings. She returned to college to earn her Ph.D. in zoology at the University of Wisconsin-Madison, and minored in epidemiology, the study of the cause and spread of disease; toxicology, the study of poisons; and water chemistry. So armed, she knew she had the background she needed to study the effect of water quality on human health.

After that, she worked in Washington D.C. as a Congressional Fellow and then as an analyst for the World Wildlife Fund and the Conservation Foundation.

Her breakout work, however, came from a long-term analysis of wildlife in areas around the Great Lakes. She began to see what Rachel Carson had noted in Silent Spring: that the population of birds in many areas was declining, but around the Great Lakes, the bird populations seemed to be normal. Her findings were chilling: birds that lived around the Great Lakes were migratory; they had been raised in other locations. When they were attracted by the water, they might stay long enough to have their babies there; but their chicks were born weak or not at all; or their chicks were unable to reproduce. Then, a fresh crop of migratory birds would be attracted to the polluted water, and the cycle would begin all over again. The Great Lakes only appeared to have a stable population of birds. It also became abundantly clear to her that environmental toxins affected the developing embryo far more than it affected adult organisms.

In the 1990s, Dr. Colborn narrowed her focus to fossil fuels and their byproducts as potential culprits in this ecological disaster. Her varied background allowed her to note the similarities between the products of fossil fuels and the carbon ring structures characteristic of human hormones. Her chemical research indicated that, due to the similar shapes of the compounds, the receptors in human cells could latch on to these fossil fuel-created chemicals as though they were hormones.

Theo Colborn

Theo Colborn and her card in the Women in Science deck.

A foreign chemical in a hormone receptor could have different outcomes depending on its effect on the receptor. The foreign chemical could have less activity than the hormone, and block the real hormone from affecting the cell. This would have the effect of deceasing hormone activity. If, on the other hand, the chemical had greater activity than the natural hormone, it could contribute to increased activity and give rise to certain hormone-related cancers such as breast cancer and testicular cancer. To those who debated whether fossil fuels were concentrated enough in the environment to cause problems, Colborn pointed to her wildlife studies, or to the well-established fact that natural hormones have dramatic influence on the body at concentrations of parts per million or even parts per trillion. Hormones, Colborn always added, are what makes us human, allowing us to develop connections to others; when they get out of balance, so does our relationship to our surroundings.

Damage to the human endocrine system in a cascade of seemingly-minor alterations that give rise to major disorders came to be known as endocrine disruption. Colborn discussed how this phenomena could potentially lead to diabetes, immune dysregulation, and obesity. She also postulated that it might be in part to blame for neurodegenerative disorders such as Alzheimer’s. Her research on PAH, a fossil-fuel byproduct, demonstrated that there were high levels in the blood of pregnant women who went on to have their babies prematurely, with smaller skull circumferences and with lower I.Q.s. By age seven, these children were more likely to be obese, have attention and behavior problems, and various kinds of metabolic dysregulation.

Colborn is also almost single-handedly responsible for the banning of PCPs in the late 1970s, chlorinated organic molecules with benzene rings. She lamented that manufacturers immediately turned to brominating or fluorinating the same exact chemicals to produce something equally hazardous that the law had not yet forbidden.

Colborn’s work and research presented a sobering picture: that of an environment permeated with chemicals for which there is little data on long-term exposure. She made it clear that this was a problem with the way that laws are written in the United States using the ‘stakeholder approach, in which “the people who are creating the problem are invited to solve the problem.” Finally, she pointed out that many toxicological studies are based on whether or not an exposed population develops cancer, although that is far from the sole negative outcome of poisoning. Endocrine disruption, she argued, was far more subtle, affecting everyone in the population to some degree, whereas cancer might only develop in some.

In the 1990s, she co-authored a book about her findings called Our Stolen Future. Like Rachel Carson, Colborn was painted as an anti-technology alarmist, though her theory of endocrine disruption was vindicated over time. She also helped disseminate information on endocrine disruption by founding the Endocrine Disruption Exchange (TEDX), an organization devoted to gathering information on endocrine disruption from journals of various disciplines and disseminating it to the public.

Doctor Colborn passed away in December of 2014, still working on her final paper, The Overlooked Connection between Human Health and Fossil Gases.

Buni, C. (2014, February). Five Questions for Dr. Theo Colborn. Orion Magazine. Retrieved from
Colborn, T. (Narrator). (2012). TED Talk: Theo Colborn’s Letter to the President [Online video]. TEDxMidAtlantic. Retrieved October 2, 2015, from
Colborn, T. (2014, November 14). The Overlooked Connection between Human Health and Fossil Gases. Retrieved from
Smith, H. (2014, December 16). Remembering the genius who got BPA out of your water bottles, and so much more. In Grist. Retrieved from

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