Perchlorates

Perchlorates have been detected in public drinking water supplies of over 11 million people in 22 states at concentrations of at least 4 parts per billion (ppb). Above a certain concentration perchlorates alter the production of thyroid hormones by the body, chemicals that are essential for proper development of the fetus and for normal metabolic functioning of the body. According to patient advocate and writer Mary Shomon, people with thyroid conditions, as well as pregnant women and their fetuses are particularly at risk. However, according to the Perchlorate Information Bureau, an industry-supported group, sound scientific and medical research shows that the low levels of perchlorate being detected in drinking water are not dangerous to human health. Still according to the same source, these studies on adults, newborns and children provide reason to believe that low levels of perchlorate (even at levels many times higher than the minute amounts being found in some drinking water supplies) also have no measurable effect on pregnant women or fetuses.
One source of perchlorate in drinking water is the past production of solid rocket propellants using perchlorate, combined with poor disposal practices. Industrial accidents and agricultural fertilizers are also suspected as sources of contamination of drinking water by perchlorate. Perchlorate is also found in breast milk at significant levels, possibly attributable to perchlorate in drinking water and foods.

The challenge of defining an acceptable level of perchlorates in drinking water sets two opposing groups with significantly different views against each other. In a draft risk assessment made in 2002 EPA suggested that levels higher than 1 part per billion (ppb) pose a health risk. In contrast, the Defense Department contended that perchlorate at 200 ppb has no lasting effect on humans. Perchlorate is one of only four of the 70 chemicals for which EPA has set public health goals that have a safety factor of 10, rather than the usual safety factors of 100 or 1000. In October 2008 EPA refused to set a drinking water safety standard for perchlorate, saying that “in more than 99 percent of public drinking water systems, perchlorate was not at levels of public health concern” using a benchmark of 15 ppb. EPA encouraged states to set their own standards in accordance to local conditions. In 2004 eight states had non-binding advisories for perchlorate in drinking water, ranging from 1 to 18 ppb. Only two states–Massachusetts and California–set legally binding maximum contaminant levels on the allowable amount of perchlorate in drinking water, at 2 ppb and 6 ppb respectively. Environmental organizations have criticized EPA’s decision not to set a federal drinking water safety standard for perchlorates. The environmental law firm Earthjustice announced that it would file suit against the Agency.

Source and  References http://en.wikipedia.org/wiki/Drinking_water_quality_in_the_United_States

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