Martin Mittelstaedt wrote an article in the Globe and Mail (F4, 20 September, 2008) on the dangers of chemicals and the ramifications on human birth rates. The article highlighted some chemicals which have been proven to have an adverse effect on human physiology, particularly the male reproductive system.

Chemical culprits

By some counts, nearly a hundred man-made chemicals either act like hormones or interfere with them, but scientists highlight four as major worries:

Bisphenol A, or BPA, the polycarbonate-plastic and tin-can-lining chemical, has been found in experiments by Frederick vom Saal and others to cause prostate abnormalities and other developmental changes linking to sex hormones in laboratory animals, at levels around and below currently accepted safety standards.

Phthalates (pronounced THA-lates), a family of chemicals used to make polyvinylchloride plastic more pliable, are found in everything from shower curtains, new car interiors to perfumes. It inhibits testosterone synthesis by interfering with an enzyme needed to produce the male hormone. Phthalates aren't embedded in products through strong chemical bonds, making them vulnerable to leaching out.

Polybrominated diphenylethers, or PBDEs, are flame retardants used in plastics, foams and electrical equipment. They are able to interfere with thyroid hormones, which are essential for proper brain and testicle development, and have been linked in animal research to attention-deficit-like conditions.

Polychlorinated biphenyls, or PCBs, are now-banned transformer-oil fluids widely used up to the early 1970s. They have a similar molecular shape to flame retardants and reduce thyroid hormone levels. Research has linked low PCB exposures to reduced impulse control and lower intellectual capacity in children. The most recent study, published in Environmental Health Perspectives in May, found that a mere one-part-per-billion increase in PCB concentration in a baby's placenta was associated with a three-point IQ drop at the age of 9.

Martin Mittelstaedt

Source: Globe and Mail