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GeoInsighter Summer
2000 Newsletter USEPA Proposes to Reduce Arsenic Drinking Water Standard Return to the Newsletter Index In May 2000, the United
States Environmental Protection Agency In its natural form, arsenic is a silvery metal that was first synthesized by medieval alchemists. Common uses for arsenic include insecticides, herbicides, and pesticides, in tanning animal hides, as pigment in paints, as a wood preservative, and as an ingredient in fireworks. Arsenic in soil is commonly encountered in orchards, where arsenic was applied as a pesticide. Low concentrations of arsenic can also be found in waste motor oil and arsenic is one of the Resource Conservation and Recovery Act (RCRA) 8 metals of interest. Arsenic also occurs naturally in some rock types found in New England. Arsenic sulfides are frequently associated with iron sulfides, such as pyrite (also known as fool's gold) in metamorphic schist rocks. A belt of sulfide-bearing metamorphic schists stretches from Connecticut through central Massachusetts and New Hampshire. Although arsenic is almost insoluble, small amounts of arsenic are released to ground water as the rock containing arsenic sulfides weathers and erodes. Therefore, ground water in some areas in New England may contain naturally-occurring dissolved arsenic, and sometimes these naturally-occurring concentrations can be above the proposed standard. According to Massachusetts and New Hampshire regulations, background concentrations of naturally-occurring arsenic do not require remediation, and a site where the detected arsenic is at background concentrations can be closed. New Hampshire and Massachusetts have generic published background concentrations of arsenic in soil. However, since naturally-occurring arsenic levels in ground water vary by location, there are no published background concentrations of arsenic in ground water, and it is incumbent on the potentially responsible party to evaluate ground water background concentrations at the site in question. This may require collecting ground water samples at presumed clean locations or reviewing ground water data at neighboring properties. The proposed change to the arsenic standard may significantly affect some areas of New England where the ground water is a potential drinking water source. In some areas where arsenic occurs naturally, it can be worthwhile to evaluate natural background arsenic concentrations to evaluate if there has been an actual release of arsenic or whether the arsenic is from natural rock weathering. Kevin D. Trainer Return to the Newsletter Index
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(USEPA) proposed to reduce the arsenic drinking water standard from the
current level of 50 parts per billion (ppb) to 5 ppb. The USEPA based
this proposal on a recent National Academy of sciences study, which
recommended that the USEPA lower the standard as soon as possible.
Although the study did not recommend a specific numeric level, the USEPA
proposed a tenfold reduction in the existing standard. If the revised
standard is accepted, the standard would apply primarily to public
drinking water supply systems; community water supplies that exceed the
new arsenic standard may be required to upgrade their potable water
treatment systems. In addition, ground water in areas identified by the
state regulatory agencies as potential drinking water supplies would
also be affected by the new standard.