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Endocrine disruption
An endocrine disruptor is a substance that interferes with the normal hormonal mechanisms that allow a biological organism to interact with its environment. In the scientific community, phthalates are broadly classified as endocrine disruptors ; while many scientific studies indicate the likelihood that phthalates behave as endocrine disruptors in human beings, the research is still in an early enough stage that it isn’t possible to make broad conclusions on the evidence.

Endocrine disruptors exhibit numerous behaviors that can make studying them a challenge. There can be a lag between when someone is exposed to an endocrine disruptor and any symptoms manifesting themselves–in particular fetal and early childhood exposure may have consequences later in adulthood. Many studies refer to this period of fetal and postnatal development as particularly important to development, but studying this is difficult; it is obviously a huge challenge to measure endocrine disruptor exposure during fetal development and then decades later diagnosing any health problems. Additionally, endocrine disruptor exposure can transmit epigenetically to one’s offspring without them being directly exposed to the endocrine disruptors. Finally, particularly low levels of exposure may still have significant effects, and exposure to multiple endocrine disruptors across a variety of compounds (not just phthalates) may synergistically combine to cause a greater effect. Evaluating the actual effects of a specific compound such as a particular phthalate requires examining cumulative exposure across multiple compounds, rather than evaluating one compound in isolation.

A popular concern about phthalate exposure is the possibility that it is the cause of a drop in male fertility . Most of the research on male fertility and phthalate exposure has been performed on animals, and studies have shown that phthalates cause abnormalities in the reproductive system, with the greatest effects when the animal is exposed during gestation and immediately thereafter. While the results on animals cannot be directly extrapolated to human beings, numerous studies on adult male humans show the similar result that phthalate exposure correlates with worsening metrics of male fertility, such as semen quality, the quantity of damaged DNA in sperm, decreased sperm motility, decreased semen volume and other metrics. Phthalates causing harm to the male reproductive system is plausible, though perhaps not to the level of doom indicated in the popular press. Additional research is needed to make a more conclusive statement.

Early research also shows phthalate exposure may be associated with diabetes and insulin resistance, breast cancer, obesity, metabolic disorders, and immune function. There are possible (though not conclusive) associations between phthalate exposure and adverse child neurodevelopment, including the development of ADHD and autistic behaviors. In many cases, there are studies that show connections between phthalates and these negative outcomes, as well as studies that show no connection; this is likely due to the research challenges outlined above, and when resolved, could show that phthalate exposure does not cause health effects, or even that they have a much greater effect than currently predicted. In all cases, larger studies are needed to demonstrate incontrovertibly what effect phthalate exposure has on human health.

A recent Nature Reviews Endocrinology review paper gives some advice for avoiding exposure to phthalates for concerned people; while they make pains to state that there is no evidence that shows this advice will positively affect one’s health, they suggest (1) eating a balanced diet to avoid ingesting too many endocrine disruptors from a single source, (2) eliminating canned or packaged food in order to limit ingestion of DEHP phthalates leached from plastics, and (3) eliminating use of any personal product such as moisturizer, perfume, cosmetics that contain phthalates. Eliminating personal products containing phthalates can be particularly difficult or impossible due to some countries such as the United States not requiring them to be disclosed in a list of ingredients.