Study Discovers Nitrate in Half of Nation’s Wells : Health: Pesticides also found in some. U.S. says the contamination levels are low and water is safe to drink.

A five-year federal study of the nation’s drinking water wells indicates that more than half are tainted with nitrates and a small number contain traces of pesticides, but officials said Tuesday that there is no “current cause for concern” about public health.

The $12-million survey by the Environmental Protection Agency, based on samples from more than 1,300 community water systems and rural domestic wells, is part of a long-term effort to assess the safety of the country’s ground-water resources.

Discovery of the widespread presence of nitrates is not surprising. Nitrates occur naturally and are released from both human and agricultural wastes as well as from the nitrogen that is a key component of commercial fertilizers.

The survey--an attempt to produce a “snapshot” of the more than 10 million wells serving rural households and 94,000 wells supplying community water systems--was designed to detect not only nitrates but 126 pesticides.

Deputy EPA Administrator Henry Habicht acknowledged that there probably are “hot spots” in prime agricultural areas such as California’s San Joaquin Valley where massive use of pesticides would result in higher pesticide levels in well water.

Even so, officials said that most of the nation’s well water is safe to consume.

“The findings of the survey indicate that the vast majority of drinking water wells in this country do not have levels of pesticides or nitrates that would pose a risk to public health,” Habicht said. “Where pesticides were detected, they were usually found at low levels--below levels of health concern. At the same time, the findings underscore the need to be ever vigilant in order to avoid more serious problems in the future.”

Based on the national sample, the agency estimated that 57% of rural domestic wells contain nitrate, while 4.2% contain one or more pesticides and 3.2% contain both nitrates and pesticides. It said 52% of community water systems contain nitrates, with 10% showing one or more pesticides and 7% containing both nitrates and pesticides.

It said that 0.6% of rural domestic wells and 0.8% of community wells contain pesticides in concentrations above maximum recommended levels.

Although EPA officials noted that adults can tolerate large exposure to nitrates, nitrate contamination is known to cause “blue baby syndrome” by reducing the ability of an infant’s blood to transport oxygen.

Potent pesticides have been linked to a variety of cancers and other disorders, and several included in the EPA survey are no longer on the market.

Representatives of several environmental organizations expressed concern over the survey’s indications of nitrate contamination and criticized it because it sampled wells at random rather than in areas where pesticide use is heavy.

“By deciding to look for contamination where pesticides were seldom or never used, the EPA seriously hobbled the survey,” said Janet S. Hathaway, a senior attorney for the Natural Resources Defense Council. “Of course, you won’t find contamination where nobody used pesticides. But both common sense and other studies show that pesticides are contaminating wells where they are heavily used.”

Because the survey was the first national attempt to assess the contamination of drinking water wells, the EPA had no basis for determining whether the situation is improving or growing worse. But officials said that the data will provide a benchmark for future assessments.

A second report, to be issued next year, will address the causes of and factors associated with well contamination.

The pesticides detected most often in the samples were associated with a herbicide marketed under the trade names of Dacthal and Fatal, used on lawns and golf courses as well as a variety of fruit and vegetable crops.

In the course of the survey, six rural wells were found to have pesticide levels above the limits set by EPA, and 32 rural wells and community wells were found to have unacceptable nitrate levels.

EPA refused to identify the wells’ owners, but officials said that they were informed of the finding within two or three days.