High nitrate levels detected in well water at five schools in Harford County isn't a risk to students and teachers who drink the water, state officials said last week.
The levels were detected in routine testing of wells at four public schools and one private school, said John Goheen, a spokesman for the Maryland Department of the Environment.
The four schools are Forest Hill Elementary in Forest Hill; North Bend Elementary in Jarrettsville; and North Harford Elementary and North Harford Middle School in Pylesville. Harford Christian School, in Dublin, a private school, is also affected.
Nitrate levels in the water at the schools range from 10 to 20 parts per million, Mr. Goheen said.
The federal Environmental Protection Agency limits the amount of nitrates in public water supplies to 10 parts per million, said Mr. Goheen.
But the EPA gives the state agency discretion to allow nitrate levels up to 20 parts per million in private water supplies that are not a main source of drinking water.
"Children, and teachers, would likely consume more water at home than at school," he said. "We've recommended the wells be tested quarterly, but the students are not in danger because it is not their primary source of drinking water."
Nitrates occur naturally in geological deposits as well as from decomposition of vegetation, he said. Other sources include runoff from fertilized agricultural areas, urban drainage, refuse dumps, animal feed lots and septic tanks.
Human consumption of nitrates occurs primarily through food, rather than drinking water, Mr. Goheen said.
Vegetables such as celery, potatoes, lettuce and spinach may contain several parts per million of nitrates, he said.
Dr. Sharin deSilva, acting administrator for the state's Environmental Health Program, said adults can eat those foods without harm because their bodies can excrete the compound.
She said nitrate levels higher than 10 parts per million in water are most dangerous for babies under 3 months old and kidney dialysis patients, who cannot excrete the compound.
In those cases, the nitrates can interfere with the blood's ability to absorb oxygen and can cause a condition known in infants as "blue-baby syndrome."
"Parents should not worry about school-age children. That should not be a problem," said Dr. deSilva. "But it would take an infant drinking formula made with water that has a high level of nitrate very few days to go downhill, and it could be fatal."
Notices containing information about nitrates and the potential danger to infants have been posted in the affected schools, Mr. Goheen said.
Albert Seymour, a spokesman for the county Board of Education, said some of the public schools that have high levels of nitrates in the drinking water also provide day-care services through the YMCA. He said notices would be sent to parents advising them of the situation.
Mr. Goheen said if further tests show any school's well contains 20 parts per million of nitrate, the school will be required to find an alternative water source, including drilling a new well or buying bottled water.
Mr. Seymour said 16 of the county's 44 public schools rely on wells. The others have public water.
It is Board of Education policy to connect a school to the public water supply if it is available in the area, as in the case of Hickory Elementary School, which will soon be connected to the county system.
Hickory Elementary shut down one of its two wells in April after tests shows 0.2 parts per billion of tetrachloroethene, a solvent, county Health Department officials noted. The federal standard is 5 parts per million.