Information AboutPerchlorate |
| CATEGORIES ABOUT PERCHLORATE | |
| perchlorates | |
| oxoanions | |
| pyrotechnic oxidizers | |
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solutions. SCIENTIFIC DEFINITION The perchlorate Ion is ClO4−. A perchlorate (compound) is a compound containing this group, with Chlorine in Oxidation State +7. STRENGTH OF OXIDATION The perchlorate ion is the weakest oxidizer of the generalized Chlorate s. Lower oxidation numbers are progressively stronger oxidizers, and less stable. STABILITY Most perchlorates, especially salts of electropositive metals such as sodium perchlorate, are slow to react unless heated, the perchlorate ion being largely Inert and not oxidizing at lower temperatures. This property is useful in many applications, such as Flare s, where one obviously does not intend the device to Explode , or even catch fire spontaneously. Similarly, the successful use of ammonium perchlorate in solid rocket engines suggests that its propensity to explode may occasionally be slightly exagerrated. Mixtures of perchlorates with organic compounds should be treated with more caution; although ''generally'' they do not catch fire or explode unless heated, ''this should not be relied on in any specific case''. PERCHLORATE IN THE ENVIRONMENT Low levels of perchlorate have been detected in both drinking water and Groundwater in 35 states in the US according to the Environmental Protection Agency . In 2004, the chemical was also found in cow's Milk in the area with an average level of 1.3 µg/L, which may have entered the cows through feeding on crops that had exposure to water containing perchlorates. According to the Impact Area Groundwater Study Program {Link without Title} , the chemical has been detected as high as 5 µg/L in Massachusetts, well over the state regulation of 1 µg/L. In some places it is being detected because of contamination from industrial sites that use or manufacture perchlorate. In other places, there is no clear source of perchlorate. In those areas it may be naturally occurring or could be present because of the use of Chilean fertilizers, which were imported to the U.S. by the hundreds of tons in the early 19th century. One recent area of research has even suggested that perchlorate can be created when lightning strikes a body of water. As of 2006, the EPA has not yet determined whether perchlorate is present at sufficient levels in the environment to require a nationwide regulation on how much should be allowed in drinking water. In 2005, U.S. EPA issued a recommended Drinking Water Equivalent Level (DWEL) for perchlorate of 24.5 parts per billion. In early 2006, EPA issued a “Cleanup Guidance” for this same amount. Both the DWEL and the Cleanup Guidance were based on a thorough review of the existing research by the National Academy of Science (NAS). This followed numerous other studies, including onewhich suggested human Breast Milk had an average of 10.5 µg/L of perchlorate. Both the Pentagon and some environmental groups have voiced questions about the NAS report, but no credible science has emerged to challenge the NAS findings. PERCHLORATE'S HEALTH EFFECTS At high levels, above 245 ppb according to the NAS, perchlorate can inhibit the thyroid gland’s ability to absorb iodine from the bloodstream. While the thyroid uses iodine to produce hormones, NAS says this process of “iodine uptake inhibition” (IUI) is not considered an adverse, or harmful affect. There has been some speculation that exposure to extremely high doses of perchlorate, for several months or years could lead to hypothyroidism, but NAS found that IUI was the only consistently documented health effect of perchlorate in humans. To put these doses into context, it is estimated a person would have to drink 400 gallons of water a day containing 20 ppb perchlorate before there could be a risk of any adverse effect. The NAS also found that perchlorate only affects the thyroid gland. There is no evidence to suggest it causes brain damage, birth defects or cancer in humans. It is also not stored in the body and any effects of perchlorate on the thyroid gland are fully reversible once exposure to these high levels stops. Currently, no water with perchlorate levels above 4 ppb is being provided to the public. There has been some concern on perchlorates effects on fetuses, newborns and children, however several peer-reviewed studies on children and newborns also provide reason to believe that low levels of perchlorate do not pose a threat to these populations. Even the American Thyroid Association reported in a press release on October 1, 2004 that perchlorate may not be as harmful to newborns, pregnant women and other adults as previously thought. (The ATA press release can be viewed at: http://www.thyroid.org/professionals/publications/news/04_10_01_perchlorate.html) The NAS, despite finding that perchlorate levels as high as 245 ppb had no effect on the body, chose to be extra cautious and suggested a safety factor of 10 be applied in determining a safe dose of perchlorate. NAS then proposed a “reference dose” (which is the amount deemed to be safe if consumed daily over a lifetime) of 24.5 ppb and declared this would be protective of even the most sensitive subpopulations. The NAS report also stated additional research would be helpful, but emphasized that the existing database on perchlorate was sufficient to make its reference dose recommendation and ensure it would be protective for everyone. TYPES OF PERCHLORATES
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