US Public Media: “Endocrine Disruptors: Today’s Canary in the Coal Mine?”

Two recent audio and video articles featuring intersex caused by Endocrine Disrupting Chemicals (EDCs) have been drawn to our attention, one released by the U.S. Geological Survey and the other by the Public Broadcasting Service:



One of the more amazing, yet troubling aspects of endocrine disruptors are their ability to change the sex, the gender of a fish. How does this happen?


These compounds are acting either as surrogates for sex hormones or interfering with the action of normal sex hormones that the fishes have. Just like sex hormones can have an effect in people, in other words, males can respond to female sex hormones and visa versa, the same thing could happen in fishes. So it’s possible that estrogenic substances can actually feminize male fish into tricking the physiological systems into producing products that a normal female would produce. In fact, it’s even possible to sex reverse fish.

Endocrine Disruption: Sex-Changing Fish and More

What have large epidemiological studies shown about endocrine disruptors and their impact on human health?

There’s some evidence for associations. It’s very difficult to prove causation. We’re not going to intentionally expose people to these chemicals, but we can show that people with higher levels of some of these chemicals may have a higher incidence of a certain kind of effect than people with lower levels of these chemicals.

Like what kind of effect?

Some of the effects that have been reported are with certain of these persistent organic chemicals. There are associations with what’s called male testicular dysgenesis syndrome. That’s a big term, but it means —

Lower sperm count?

— lower sperm count; increases in hypospadias, increases in cryptorchidism, which is undescended testicles. … These are male problems with the male reproductive tract that are caused by exposure very early in life, probably in utero.

Exposure to what?

Exposure to a number of different kinds of chemicals that may either mimic estrogen, so it’s like too much estrogen, or it may be blocking the androgen system. Our body has a very, very fine balance between the levels of androgens and the levels of estrogen, and if you upset the balance, you can have adverse effects. So that’s just one example. …

We know that developmentally, the thyroid hormones being at the appropriate level are absolutely essential for normal brain development. And yet we’re finding that certain chemicals like PCBs and now the flame retardants — there are reports of their being associated with alterations in the normal level of circulating thyroid hormones. …

We know that endocrine disruptors can cause adverse effects in human populations, and we know that from the studies of certain drug situations. DES, which was used from the ’50s through the early ’70s to prevent miscarriage, was associated with adenocarcinoma, a kind of very rare vaginal cancer in young girls. DES also causes in women who took it when they are postmenopausal an increase in breast cancer, and appears to be causing an increase in breast cancer in the DES daughters. It appears to be causing effects in the DES sons. Many of these effects we would never have noticed or known about had it not caused this very rare cancer in young women.

So the point that I’m making is you kind of have to look. Otherwise you don’t see these things.

Endocrine Disruptors: Today’s Canary in the Coal Mine?