From: David A Gabel, ENN
Published July 14, 2011 09:41 AM

Chemicals Found in Household Products Linked to Thyroid Hormone Disruption

Phthalates and Bisphenol A (BPA) are chemicals that are commonly found in plastics and household products such as solvents and cleaners. Being common in places that people live and eat, they will eventually make their way into the body. A new large study out of the University of Michigan at Ann Arbor has linked the abundance of these chemicals in the human body with thyroid function. Disrupting the thyroid's proper functioning can affect many important body systems such as reproduction, metabolism, and energy levels.

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Phthalates are mainly used as plasticizers, increasing the flexibility, transparency, and longevity of plastics. BPA is an organic compound that is known to be estrogenic that is also used in plastics and other household items. Both are known as health hazards and some countries have even banned them as toxic substances. Phthalates are being phased out in the developed countries of Europe and North America and Australia. BPA is banned in baby bottles throughout these countries and completely banned in Canada.

Researchers conducted a large-scale human study to see how phthalates and BPA affected thyroid hormone levels. They used data from the US National Health and Nutrition Examination Survey to compare metabolites and serum thyroid measures from over 1,600 individuals. In general, they found higher levels of the plasticizers were associated with higher levels of the thyroid measures.

They found one type of phthalate, DEHP, which caused the strongest disruption of the thyroid. Their research showed that the primary exposure to DEHP was through the diet. The individuals in the top 20th percentile of DEHP concentration, had their thyroid hormone levels increase by up to ten percent. Those in the bottom 20th percentile had a decrease in thyroid hormone level of up to ten percent.

The study focused mainly on adults but the researchers emphasized that the effects of these plasticizers can have a much greater effect on pregnant women and children. According to lead author of the study, John Meeker, fetal and child development may be particularly vulnerable to disruption in thyroid hormone levels associated with exposure to environmental chemicals.

The thyroid hormone's primary responsibility is for the regulation of metabolism, the process by which we turn food into energy. It is essential to proper development and differentiation of all cells in the human body. They regulate protein, fat, carbohydrate and vitamin metabolism, and body heat. Disruptions by phthalates and BPA may not be fatal initially, but they will mess with the inner body's workings.

The study can be found in the journal, Environmental Health Perspectives.

Link to published article: http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info%3Adoi%2F10.1289%2Fehp.1103582

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