Most of the attention on phthalates, a group of hormone-disrupting chemicals found in PVC plastics, has been focused on fetal and child health, particularly regarding genital and behavioral development. Recent data have shown, for example, “incomplete virilization in infant boys” and reduced masculine play as they grow up, and for girls, an earlier onset of puberty. What about affecting hormonal function in adults?
Men exposed to high levels of phthalate had lower testosterone levels, but that was for workers in a plastics plant. In the general population, the evidence is mixed. A study in Sweden of men in their 20s found no effect on testosterone, whereas a U.S. study on men in their 30s did find an effect, even at levels of exposure much lower than those of factory workers.
When there’s conflicting evidence like this, ideally we’d put it to the test, but you can’t ethically expose people to phthalates, so scientists have come up with convoluted methods like implanting the testicles from human fetuses into mice to keep them growing. We want to know about the effects on adult, not fetal, testicles, which had been harder to procure until recently. “[C]onsent was obtained from all donors.” Now, I’ve heard of blood donors, but this is a whole other level. Researchers obtained donated testicles from prostate cancer patients who underwent castration to control their disease and, indeed, were able to get direct evidence that phthalates can inhibit testosterone production at the kinds of levels one sees in general population studies.
What about breast cancer, the number-one cancer killer of young women? Women working in automotive plastics and food canning are at five times the odds of breast cancer, suggesting a link. In a petri dish, however, phthalates didn’t seem to accelerate breast cancer growth at the levels of exposure expected in the general population. More recently, though, phthalate exposure was found to boost breast cancer cell growth in vitro at the levels found circulating in the bodies of many women. Therefore, the maximum tolerable dose set by governments should be re-evaluated.
How do you avoid the stuff? Well, when you think of plastic chemicals, you may think of water bottles, but they appear to play only a minor role. Most phthalates come from food. How do we know this? If you take people and have them stop eating for a few days, you get a significant drop in the amount of phthalates spilling into their urine. Fasting isn’t exactly sustainable, though. Thankfully, we can see similar drops from simply eating a plant-based diet for a few days, which gives us a clue as to where most phthalates are found. There were a few cases of spikes within the fasting period after showers, however, suggesting contamination in personal care products.
We can counsel patients to reduce phthalate exposures by avoiding the use of scented personal care products, soaps, and cosmetics, since phthalates are used as a fragrance carrier. Phthalates can also be found in children’s toys, as well as adult toys. “On behalf of the Danish [Environmental Protection Agency] EPA, [the Danish Technological Institute] DTI has made inquiries about the consumption pattern in connection with the use of sex toys made of rubber or plastics” to see what kind of exposure one might get “based on worst case scenarios.”
It turns out that “jelly” is plasticized PVC—up to two-thirds phthalates by weight. Though the use of water-based lubricants may reduce the health risks 100-fold, phthalate exposure through lubricants may still have the opposite of the intended effect. Women with the highest levels of phthalates flowing through their bodies “had over 2.5 times the odds of reporting a lack of interest in sexual activity,” and these weren’t women in a canning factory, rather they were at typical exposure levels in America.
Michael Greger, M.D.
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