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Researchers have identified 15 chemicals that may be linked to earlier menopause.
Women with the highest levels of these chemicals in their bodies went through menopause anywhere between two and four years earlier than women with the lowest levels, the team at Washington University in St. Louis found.
The study adds to a growing body of evidence linking so-called endocrine-disrupting chemicals to a range of effects in people — although they cannot show that the chemicals themselves are actually causing the changes.
“Overall, women with the highest endocrine-disrupting chemical levels had ages of menopause 1.9 to 3.8 years earlier than those without,” the researchers wrote on their report, published in the Public Library of Science journal PLoS ONE.
“My hope is to not scare women. My hope is to raise awareness."
The good news is that many of the chemicals have been banned or are limited in their use. The bad news is that several are still in the environment and hang around for decades — they’re called persistent environmental pollutants.
“My hope is to not scare women. My hope is to raise awareness,” said Dr. Amber Cooper, an assistant professor of obstetrics and gynecology at Washington University, who led the study. The study doesn't offer any guidance on what women could do to reduce their exposure.
Another bit of good news is the study also found little evidence linking dozens of other chemicals with early menopause, including many of those used in common household products.
And one important point — the study showed what’s called an "association." Just because the women had the chemicals in their bodies does not mean those chemicals caused them to go through menopause early. Smoking is also strongly linked with early menopause, which in turn is linked with heart disease and osteoporosis.
Cooper and colleagues looked at data from 31,575 people who took part in a giant Centers for Disease Control and Prevention survey from 1999 to 2008. They included 1,442 women who had gone through menopause and who had been tested for levels of endocrine-disrupting chemicals.
The 15 chemicals most likely to be in either the blood or urine of women who had earlier menopause include pesticides, a batch of now-banned chemicals called PCBs, and two phthalates in a group called DEHPs.
“Although these chemicals may not be currently in production, there is likely still an ongoing exposure to many of these pervasive chemicals from our environment with an associated threat to human reproductive health,” the researchers wrote.
Those last two phthalates are used in many common household products, however. They’re used to make plastic more flexible and are found in tablecloths, floor tiles, upholstery, shower curtains, garden hoses, swimming pool liners, rainwear, baby pants, dolls, some toys, medical tubing, and blood storage bags.
Nine of the chemicals identified in the study were polychlorinated biphenyls, or PCBs for short. They are chemicals that were widely used in construction and to make electrical materials before their production was banned in 1979 because they cause cancer. But they are still used, and can be found in waste dumps and sometimes even in sewage that's spread onto agricultural fields — most recently in 2013 in South Carolina.
Women with high levels of these 15 chemicals were six times more likely to have gone through menopause than women the same age who didn’t have high levels.
“One of the greatest difficulties in studying these chemicals is that we don’t know what they might do in combination.”
“At the end of the day, I think the most important thing is to stress this is just a study we hope raises awareness. It’s a study that cannot prove causation,” Cooper told NBC News.
For one thing, the women in the study were tested after they had gone through menopause. Some of the chemicals are processed quickly by the body. Phthalates, especially, pass through the body quickly. So women could have been exposed at some point and then their bodies got rid of the chemicals.
“We can’t say this was their exposure over the previous 30 years,” Cooper said.
It’s also possible that some women’s bodies handle the chemicals differently than others do.
Scientists have been trying to understand how various chemicals might affect the body. Endocrine disruptors might work through a variety of mechanisms — by damaging a woman’s ovaries, or perhaps even by speeding up the production of eggs cells so a woman runs out of eggs earlier in life and goes into menopause.
“We sort of group them together because they are chemicals that kind of interfere with how your body makes hormones,” Cooper said. “One of the greatest difficulties in studying these chemicals is that we don’t know what they might do in combination.”
Several researchers not associated with the study also pointed this out, but said the finding do suggest avenues for further research.