Middle-aged men and women who are exposed to high levels of certain chemicals found in plastics have reduced levels of testosterone, according to a new study published in the Journal of Clinical Endocrinology.
Testosterone is the primary male sex hormone, and it plays a vital role for both men and women in biological processes, including physical growth and strength, bone density, brain function, libido and cardiovascular health.
Phthalates are chemicals added to plastics to make them softer and more flexible (in shower curtains, for example). They also crop up in products from shampoo to laundry detergent to the coating on electrical wires. They’re widespread in the environment, and previous testing has shown that 90 percent of adults have detectable levels in their bloodstream.
The new study showed that adults in midlife may be particularly vulnerable to the chemical’s harmful effects. “Phthalates do not appear to accumulate in the body,” says study author John Meeker, associate professor of environmental health sciences and associate dean for research at the University of Michigan School of Public Health. “But since these chemicals are nearly ubiquitous it is possible that repeated daily insults throughout life, in addition to other age-related physiologic changes, may make older adults more susceptible to exposure.”
Phthalate Exposure and Testosterone
Declining levels of testosterone are a normal part of aging, but previous research has suggested that men today have lower serum testosterone levels than their counterparts two decades ago.
In this study, Meeker and his team looked at the association between phthalate exposure and testosterone levels in 2,208 people of all ages by examining urine and blood samples.
They found that those with the highest levels of phthalates in their bodies had the lowest levels of testosterone. The effect was most noticeable in boys aged 6 to 12, and men and women aged 40 to 60. Interestingly, the biggest association was seen in women — those with the highest level of phthalates were associated with a 10.8 to 24 percent decline in testosterone.
“One surprising finding was that we did not observe significant associations among men ages 20 to 40, an age group for which previous research has reported a relationship,” says Meeker. “We did, however, find that some phthalates were associated with decreased testosterone among men ages 40 to 60. We were also surprised that associations among women ages 40 to 60 were among the strongest.”
Research linking phthalates to negative health effects is not new. “This study is just another [finding] among the list of concerns,” says Paul Pestano, a research analyst with the Environmental Working Group, an organization that works to inform and empower the public to live healthier lives. “In addition to decreasing testosterone, phthalates have also been linked to lower sperm count, less mobile sperm, birth defects in the male reproductive system, obesity, diabetes and thyroid irregularities.”
Protecting yourself from phthalates can be complicated because they’re so widespread — they’ve been dubbed the “everywhere chemical” — and, as Meeker notes, “most products that contain phthalates aren’t labeled as such.”
But there are three things you can do when it comes to these noxious chemicals:
Choose personal care products carefully. Phthalates are often a secret component of "fragrance," which appears on the ingredient list of many personal care products for men and women. Manufacturers don’t have to disclose what’s in a fragrance because it is considered a trade secret. Consumers can use the Environmental Working Group’s comprehensive Skin Deep Cosmetics database to find the safer products.
Avoid processed foods. “Food is actually a primary source of exposure to certain phthalates,” says Meeker. “And there is evidence that taking strides to eat fresher foods that have undergone less processing and packaging may reduce exposure.” Plastic food containers and plastic wrap marked with the recycling label “#3” also contain these toxic chemicals. Eliminate plastic food storage containers when possible, and always avoid heating food in plastic containers.
Dust often. Due to phthalates ubiquity in household products, particles can live in the dust that settles on your piano or behind the TV. “We encourage consumers to frequently vacuum and dust their homes,” says Pestano.
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