Chemicals commonly used in the manufacture of plastic appear to affect thyroid hormones in humans. These compounds include phthalates and BPA (bisphenol A). An analysis of urinary levels in adults and teens found that people with the highest levels of phthalates and BPA had lower levels of free T4 and higher levels of TSH. These measurements suggest impaired thyroid function in people exposed to such chemicals.
The People's Perspective on Medicine