Your dust is hormonally active. (Yes, you read that correctly.)

Over 200 industrial chemicals are now readily detectable in the blood, breast milk, or urine of Americans and of most people in industrial nations around the world. Many of these chemicals come from the products we use in our buildings. These chemicals migrate out of their products and into the air and dust in our homes, offices, and schools. And, in a study we did at Harvard, every single dust sample collected from forty-six different building spaces was hormonally bioactive. 

Some of these chemicals can cause testicular cancer. Others affect sperm count. Others have been associated with failure of testes to descend in babies. That’s the story for men. 

The assault on women’s health from these chemicals also extends to their reproductive health. Some chemicals commonly found in buildings have been associated with increasing the likelihood by twofold that it will take a year or longer to become pregnant, more likely to report irregular menstrual cycles, and higher risk of developing thyroid disease—a risk that was threefold higher for women postmenopause.

This story starts in the mid-1970s, with the use of “PBBs” – chemical flame retardants used in plastics found in televisions and in foam found in couches and chairs. A chemical company that sold PBBs in the 1970s, Michigan Chemical Company, also sold animal feed supplement. A shortage of preprinted bags at the packaging plant led to an accidental mislabeling, and bags of PBBs were shipped out as cattle feed supplement. Want to hazard a guess as to what happened next? Farmers and ranchers reported animals with a loss of appetite (go figure . . .). Then things got bad. These PBBs are lipophilic chemicals—literally “fat loving.” As the cows ate the PBBs, they stored the chemicals in their fatty tissue. It was months before the mislabeling issue was discovered, and by that time PBBs had lodged themselves into the fatty tissue of millions of animals in the food chain. Humans, at the top of that chain, were the final repository of these PBBs.

The remedy? PBBs were banned and millions of animals had to be culled. But it was too late— by then, anyone consuming meat in Michigan was consuming those PBBs and, just like the animals, storing those PBBs in their own fatty tissue. The result? The people of Michigan were unwilling participants in a great human toxicological experiment. The environmental persistence of PBBs and their ability to store in our bodies meant that this was not a problem that went away quickly.

60 percent of people tested in Michigan in the 2000s still had levels of PBBs in their bodies that were higher than 95 percent of the rest of the US population. Women with higher levels of PBBs in their blood had fewer days between menstrual cycles, more days of bleeding, lower estrogen levels, and higher rates of breast cancer.

But that’s not where things ended.

It turns out that kids born to parents from Michigan have PBBs in their blood, despite being born after the ban went into place. Their moms passed these PBBs to them through the womb and through breastfeeding. Boys born to moms with higher levels of PBBs in the body reported more genital and urinary issues. Girls born to moms with higher levels of PBBs in the body started menstruating a year earlier than their peers. When these girls became women of childbearing age, they were more likely to suffer miscarriages.

Three generations have been affected. 

Knowing that PBBs are toxic to animals; knowing, based on research published in 1978, that PBBs cross the placenta and are teratogenic (that is, that they can alter the normal development of an embryo or fetus), and possibly carcinogenic; and seeing that the populace was rightly outraged after the Michigan debacle, what was the industry response? Add an oxygen in the middle of the molecule and create a “new” brominated flame retardant to be used just like PBBs—in couches, chairs, mattresses, and plastic casings around televisions and computers.

From the perspective of the market, and regulators, this was a new chemical with a new name. No longer PBBs, but PBDEs—polybrominated diphenyl ethers. PBDEs were used from the early 1980s through the mid-2000s, much of that time escaping the notice of health scientists and the public.

It wasn’t until a Swedish study was published in the early 2000s that concern started to rise. In that study, researchers looked at breast milk samples from a biobank, which had stored samples dating back to the 1970s. These scientists noticed an exponential rise in the level of this “new” chemical in the breast milk. (New to researchers, anyway; the industry certainly knew about it.) This sparked intense interest from researchers—a “scientific feeding frenzy.”  The scientific process followed a familiar pattern, asking and answering a series of questions. 

Where were these chemicals in our environment?

(Answer: in air and dust in every home, office, school, and place we looked, including in polar bears, eagles, and sea turtles.)

Could they be found in humans?

(Answer: yes. They are detected in the blood of nearly everyone.)

Were they determined to be toxic in animal studies?

(Answer: yes. PBDEs interfere with thyroid hormones and affect neurodevelopment reproductive systems.)

Was that enough to ban them? 

(Answer: no. Claims were made that the results of animal studies do not represent human health effects.)

Were human health effects found in the subsequent human studies?

(Answer: yes. Surprising no one, the human studies found what the animal toxicology studies found: impacts on the thyroid, neurological development, and reproduction.)

This body of research on PBDEs took more than a decade to accumulate. In the end, after 30 years of use and widespread global contamination, for 20 of which they were entirely off the radar of health scientists, PBDEs were banned.

If you think the story ends here, you haven’t been paying attention.

Next up in the “chemical whack-a-mole” chain were halogen-free organophosphate (OP) flame retardants. The idea that these OP flame retardants were “safer” was soon debunked. A study showed that OP flame retardants were associated with severe adverse reproductive issues, including a decreased likelihood of fertilization and embryo implantation and a decreased likelihood of having a clinical pregnancy. It gets worse—if you were lucky enough to get pregnant, those with higher levels of OP flame retardants in their body were less likely to have a live birth.

Do we need these flame retardants? It turns out that our massive global experiment in flame retardants was thrust on us by an intense industry lobbying effort in the 1980s that aimed to take the focus off cigarettes as the core cause of an increase in the number of house fires and redirect that focus to the products that caught fire. In an outstanding six-part series called “Playing with Fire” published in 2012, the Chicago Tribune uncovered the work of tobacco lobbyists as they pushed to limit regulations that favored self-extinguishing cigarettes in favor of putting flame-retardant chemicals in . . . well, everything. The award-winning series shows how these lobbyists relied on, and promoted, faulty science and testimony from an unscrupulous doctor who fabricated tales of children burning in fires, among other tried and true tactics intended to manufacture doubt. This led to the widespread and global use of flame-retardant chemicals in couches, chairs, curtains, televisions, remote controls, drywall, computers, pillows, and on and on. Another gift from Big Tobacco.

Flame retardants are just one of many examples of harmful chemicals in our products – stain repellent “Forever Chemicals” (linked to cancer and weight gain in women) and plasticizers like phthalates (linked to the absence of the epididymis (testicular duct that carries sperm), opening of the urethra on the underside rather than the tip of the penis (hypospadias), premature breast development, and asthma in kids.)) are two more.

We need a full reckoning of ingredients in our buildings and products. We would be wise to heed the words of Rachel Carson from 50 years ago: “If we are going to live so intimately with these chemicals—eating and drinking them, taking them into the very marrow of our bones—we had better know something about their nature and their power.”

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Excerpted from Healthy Buildings, How Indoor Spaces Can Make Us Sick – or Keep Us Well”, by
Joseph Allen and John Macomber


  • Dr. Joe Allen is associate professor at the Harvard T.H. Chan School of Public Health, director of Harvard’s Healthy Buildings Program, and coauthor of Healthy Buildings: How Indoor Spaces Can Make You Sick—or Keep You Well. Dr. Allen serves on Harvard’s Presidential Committee on Sustainability, he keynoted the White House’s first ever Indoor Air Quality Summit, is an advisor to The White House Office of Science and Technology Policy, and during the COVID-19 pandemic, served as Commissioner of The Lancet COVID-19 Commission and Chair of its Safe Work, Safe Schools, and Safe Travel Task Force. In 2023, Allen was featured on the 60 Minutes episode, The Air We Breathe, spotlighting the value of healthy indoor air quality for virus mitigation. He has authored over 100 peer-reviewed scientific papers, and regularly contributes to the New York Times, Washington Post, and Harvard Business Review.
  • John D. Macomber is Senior Lecturer at Harvard Business School and a world leader on the financing of resilience. He is the author of dozens of HBS case studies on infrastructure projects, focusing on office buildings in the United States, housing in India, water management in Mexico, and private sector–led new cities in Asia.