To truly assess the risks posed by a ubiquitous group of chemicals found in everything from vinyl shower curtains to bug spray, researchers need to study their cumulative impact on human health, declares a new report from the National Research Council, a group that advises the government on science and health policy. The chemicals, called phthalates, are used to make plastic products soft and flexible, and are also found in cosmetics, personal-care products, and even pharmaceuticals. In rodent studies exposure to phthalates has been shown to interfere with the development of the male reproductive system, causing
infertility, reduced sperm production, undescended testes, penile birth defects and other reproductive-tract malformations [Science News].
Traditionally, health agencies have studied the risk of each chemical individually, but experts say such a process doesn't accurately reflect human exposure.
"It is extremely important to conduct cumulative risk assessments to protect public health," said [phthalate researcher] Dr. Sheela Sathyanarayana.... "Unlike in scientific experiments, humans are exposed to multiple chemicals everyday," she said, so combining the chemicals "can help identify how these multiple exposures could be leading to health outcomes in the general population" [Scientific American].
Studies from the Centers for Disease Control and Prevention and independent scientists have found phthalates in virtually everyone, including pregnant women and babies [USA Today].
Researchers are particularly concerned about males' exposure to the chemicals because they act as anti-androgens, lowering the level of testosterone in the body. While the male reproductive system is still developing, when the embryo is in the womb and then as an infant, the risks of exposure are thought to be particularly high.
Phthalates have been used in toys, cosmetics, personal-care products, food packaging, pharmaceuticals, medical devices, and cleaning and building materials. They have been found in products such as teethers and pacifiers that babies put in their mouths. President George W. Bush signed a law this year banning three types of phthalates in children's toys and child care items, except for minute amounts, while temporarily banning three others pending further study. The same six phthalates have been banned in European toys for nearly a decade [Reuters].
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