Reporting from Washington — The Environmental Protection Agency took steps Wednesday to curb toxic substances in drinking water, including perchlorate, a chemical thought to threaten the thyroid gland that has contaminated hundreds of public water wells, mostly in California.
The agency also moved to set standards for 16 other substances that can invade water supplies and impair human health.
Perchlorate, a remnant of California's manufacturing, aerospace and military bases, can inhibit thyroid hormone production, especially in fetuses and infants. That can lead to lower IQs and developmental delays, studies have shown.
Research by the Food and Drug Administration, among others, found perchlorate contamination in food and water in 45 states, and a small study in the Boston area found perchlorate in the breast milk of nursing mothers.
Sen. Barbara Boxer (D-Calif.) hailed the EPA's action, saying it was about time the government moved "to protect our families from perchlorate."
"Exposure to perchlorate in drinking water is dangerous, especially for pregnant women, infants and children," said Boxer, chairwoman of the Senate Environment and Public Works Committee.
But Republicans on the committee disputed the threat.
The "EPA has changed its position," one senior Republican Senate staffer said. "That's not good policy. Nothing new is being presented as far as the science goes."
The George W. Bush-era EPA refused to regulate perchlorate, which occurs in nature but is also man-made.
In the past, industrial users of perchlorate commonly dumped it into unlined pits, from which it leached into groundwater, scientists say. The most heavily affected areas have been Los Angeles, Riverside, San Bernardino, Orange and Sacramento counties.
California law requires that perchlorate levels be below 6 parts per billion. It was unclear what the federal limit would be.
Late last year, a contaminated well in Barstow had a level of 100 parts per billion.
After taking public comment, the EPA will issue a formal rule on perchlorate levels. The process could take two years, EPA Administrator Lisa P. Jackson said.
Meanwhile, late Wednesday, congressional Republicans prepared to introduce legislation to prevent the EPA from regulating greenhouse gas emissions that scientists say contribute to global warming.
Rep. Fred Upton (R-Mich.), chairman of the House Energy and Commerce Committee, and Sen. James M. Inhofe of Oklahoma, the ranking Republican on the Senate Environment and Public Works Committee, issued a draft of a measure that would strip the EPA of its ability to regulate greenhouse gas emissions under the Clean Air Act and to conduct research into climate change.
The draft measure adds to a growing pile of bills by Republicans and some Democrats to hamstring the EPA on climate change.
Jackson said the cascade of proposed legislation had not persuaded the administration to change course. "The president's advisors would advise him to veto any legislation that … would take away EPA's greenhouse gas authority," she said after testifying before the Senate environment panel Wednesday. "Nothing has changed."
The Obama administration, unable to get Congress to act on a climate bill, has been pushing the EPA to regulate emissions using its authority under a 2007 Supreme Court decision.