The state Department of Environmental Protection proposed yesterday the nation's toughest standard for perchlorate, a chemical used in explosives that was found in 10 public water sources in 2004. The drinking water limit of 2 parts per billion would be dramatically stricter than a proposed level of 24.5 parts per billion, announced by the US Environmental Protection Agency in January.
The Department of Environmental Protection commissioner, Robert W. Golledge Jr., said the federal limit does not take into account that people can ingest perchlorate from other sources, such as lettuce, grains, vitamins, and breast milk, where the chemical has also been found.
Perchlorate can affect normal function of the thyroid gland, and thus can interfere with metabolism and growth and development. Golledge said Massachusetts has spent four years seeking the best standards to protect vulnerable populations, particularly children and pregnant women.
The proposed regulations, to be the subject of a series of public hearings this spring before taking effect, are about 10 times tougher than limits in a National Academy of Sciences report last year.
That report, on which the EPA guidelines are based, concluded that perchlorate is far less toxic than first believed, suggesting that limits could be set higher than 20 parts per billion, although risk would vary on body weight and consumption.
Golledge defended the state's proposed limit. ''We are taking a very cautious and protective approach . . . and it is the prudent and appropriate standard to take," he said.
Perchlorate, which has been widely used on military bases since the 1940s, has generated concern among environmentalists and consumers because it can interfere with the thyroid gland, posing a particular risk to children. It has been discovered in 35 states and has become a deeply divisive political issue as environmentalists say the federal government has delayed rules and proposed lax standards because much of the contamination is on military bases.
An EPA aide said last night that the federal agency's proposed standards were based on the nation's foremost science advisory committee.
Because of the lack of clear federal guidelines -- for example, the EPA says its guidance is for cleaning contaminated sites and is not designed with the specific intent of protecting drinking water -- and conflicting health studies, states are considering varying standards. California has set a public goal of 6 parts per billion in drinking water, Arizona has provided ''guidance" of 14 parts per billion, and New Jersey is expected to soon announce a proposed enforceable standard of 5 parts per billion. Massachusetts had recommended a limit of 1 part per billion before the National Academy study was released.
Yesterday, several officials in Massachusetts communities that have tested positive for perchlorate praised the state's decision, saying they felt it was protective, but also allowed some leeway in the case that safe, but trace levels of the chemical are found in water supplies.
''I'm happy; 2 parts per billion is a far more reasonable standard than one," said Tewksbury's town manager, David G. Cressman. He said the town's perchlorate problem, which had registered above 3 parts per billion in 2004, had stemmed from waste that a manufacturer was discharging. The problem was corrected at a cost of $50,000, the water was retested, and the supply has been back on line for 15 months.
It is unclear how many of the state's public water supplies -- defined as serving at least 25 people more than 60 days a year -- now have perchlorate problems. The last study the state did was in 2004, turning up elevated perchlorate levels in excess of the advisory of 1 part per billion in 10 communities around the state, from Williamstown to Westport.
The other municipalities that had elevated levels in at least one well that was part of the public water supply in 2004 were Boxborough, Boxford, Chesterfield, Hadley, Millbury, Southbridge, Tewksbury, and Westford. The state said the affected water supplies were either treated or the water sources were shut down.
In Millbury, for example, a private well owner that services the community installed a system at a cost of more than $1 million that has resulted in nondetectable levels of perchlorate. Other communities used bottled water and issued health warnings.
Environmentalists praised the regulation, but questioned why it was double the advisory standard. ''It appears to be a strong standard, a strict one," said John McNabb, water policy specialist for Clean Water Action, an advocacy group. ''But the jury is still out on why it went from 1 part per billion to 2."
Golledge said the reason is simple: First, exhaustive research by his staff shows that 2 parts per billion is extraordinarily protective. Second, chemicals used to treat drinking water can sometimes increase perchlorate levels to just over 1 part per billion.
Massachusetts has aggressively tested drinking water supplies since trace levels of the contaminant were found in Bourne test wells in 2002, probably having leached from the adjacent Massachusetts Military Reservation, where grenades and rockets containing the chemical were used. Since then, however, it has been found in water supplies that had construction blasting nearby.
The state plans to hold six public hearings on the proposal in April; the first is scheduled for April 10 in Bourne. The public comment period is scheduled to close May 12.