Australasian Science: Australia's authority on science since 1938

Organic Pollutants Linked to Early Menopause

By Australian Science Media Centre

A new study has found that women who are exposed to high levels of endocrine-disrupting chemicals begin menopause 2–4 years earlier.

“A number of chemicals that are persistent pollutants in the environment, such as polychlorinated biphenyl’s (PCB’s) and phthalates, can weakly mimic oestrogen or testosterone. As they are easily absorbed and can accumulate in the body, these chemicals may accumulate to levels that have adverse effects on human health.

“This study looks at the occurrence of early menopause in a sample of US women with levels of a variety of persistent organic pollutants that can mimic oestrogens’ effects. The study found that women who had high levels of PCBs, some pesticides or phthalates in their urine (higher than 90% of women in the general community) went through menopause between 6 months to 3 years earlier than women in the general community. The amount menopause was shifted by, and the statistical strength of the association, varied quite a bit even in the same chemical class. When the researchers tried to control for the length of time the women had been exposed to these chemicals, the association disappeared for phthalates and some of the pesticides, but remained for PCBs.

“While the associations are suggestive, correlation studies suffer from the problem that other factors may be involved. However, these results are concerning and should be carefully considered with a view to reducing PCB exposure in people with the highest levels of PCBs. This is already occurring to some extent: the latest US National Health and Nutrition Examination Survey shows that exposures to phthalates at least has fallen by around 45% from the levels examined in this study.”

Dr Ian Musgrave is a Senior Lecturer in the Faculty of Medicine, School of Medicine Sciences, within the Discipline of Pharmacology at The University of Adelaide.

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“Endocrine-disrupting chemicals are substances that interfere with the normal hormonal processes in the body. This study used a relatively small sub-sample from a large US population-based study to investigate whether exposure to endocrine-disrupting chemicals, such as pesticides and polychlorinated biphenyls, were associated with an earlier age of menopause.

“Fifteen organic pollutants were identified as being associated with an early menopause – with the earlier onset in those with the highest exposure ranging from 1.9 to 3.8 years, depending on the specific chemical. The study was cross-sectional and so cannot demonstrate cause and effect, however it does provide an important starting point for future research.

“Chemicals that affect ovarian function could have serious implications for women’s health and fertility at the population level. To date there has been limited research in Australia on the exposure of individuals to organic pollutants and other endocrine-disrupting chemicals. More research is needed to identify the sources of exposure – to pinpoint where these chemicals are found in our diets or home environments – as well as to measure any potential associated health effects.”

Dr Anna Callan is a lecturer in the School of Medical Sciences, Faculty of Health, Engineering and Science at Edith Cowan University.

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“This is an important paper and adds to the growing evidence that there are a number of environmental chemicals that disrupt the balance of reproductive hormones and reproductive function.

“Whether the observed effect of an earlier menopause represents organ-specific effects (i.e. that these compounds are toxic to the ovaries) or a general toxicity of these compounds is not yet known.

“A limitation to the study is that it relied on women’s recall of when their menopause occurred. The authors have suggested that such recall is pretty accurate, but in the study they quoted, 25% of women were at least 2 years out in their recall of when their menopause actually occurred. As that study included women who had experienced a surgical menopause (these women may have been more accurate in their recall) there is a concern that more than 25% of the women may have made an incorrect recall of at least 2 years, give or take. However, the findings reported here are consistent with another recent study that reported that higher phthalate levels were associated with lower testosterone levels in women aged 40–60 years (Meeker et al. 2014).

“These compounds are ubiquitous in our 21st century environment and, as the authors say, research into the health consequences of exposure to these endocrine-disrupting chemicals should be prioritised. These chemicals not only pose a potential threat to human health, but to the health of all living creatures.”

Professor Susan Davis is a National Health and Medical Research Council (NHMRC) Principal Research Fellow and Professor of Women’s Health in the School of Public Health and Preventive Medicine at Monash University.

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“The good news is that most of the chemicals involved in this study have been banned for almost a decade under the Stockholm Convention, and their concentrations in the environment – and in our body burdens – are declining.

“Looking at the reported results, I think that age at menopause could be affected by many things, not just those that the researchers controlled for when they surveyed their populations. Industrial chemicals could be involved but, as with epidemiological studies of this type, all that can be observed is an ‘association’. The authors do say this but their enthusiasm is sometimes misplaced, since 45–55 are hardly prime years for expression of fertility.”

Professor Ian Rae is an Honorary Professorial Fellow at The University of Melbourne and Former President of the Royal Australian Chemical Institute.

Original study published at http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0116057