Lead levels in New Haven tap water are within state and federal limits but may sometimes reach unhealthy levels.

According to data collected by the Environmental Working Group in 2009, lead in water from the South Central Connecticut Regional Water Authority — which services over 400,000 residents in New Haven and surrounding towns — were found at levels above the safe level recommended by the Environmental Protection Agency. South Central Connecticut water quality supervisor Tom Barger said the lead levels in New Haven tap water are safe and the company takes testing seriously.

“Is our water safe from a lead perspective?” Barger said. “Absolutely.”

The average lead level in New Haven tap water from 2004 to 2008 was 0.12 parts per billion, which was below the recommended health limit of 0.2 parts per billion. But for eight tests out of 139 during the time period, the lead content rose above the recommended health limit. According to the water authority’s annual water quality report, lead levels in excess of the legal limit of 15 parts per billion may cause delays in the physical or mental development of infants. In children, excess lead levels can cause slight deficiencies in attention span and learning abilities, and in adults, it may cause kidney problems or high blood pressure.

This data represents lead testing from a combination of sites, including the water source, the distribution system and private homes, Barger said. In 2008, the South Central Connecticut Regional Water Authority performed more than 110,000 tests on over 10,000 water samples. Barger said the authority works hard to make sure its water is safe for consumption.

While the water authority tests for lead at the water source every two weeks, it tests for lead at a minimum of 50 homes every three years, said water quality official Don Menzies. Customers are told to let their water sit in the pipes for at least six hours, and then they are asked to fill up a kit with the water, he said. Because many pipes have joints soldered with lead, if water is allowed to sit for too long within those pipes, lead can seep into the water and alter the results, he said.

The highest lead level reported in the data — 13 parts per billion, only 2 parts per billion away from the legal limit of 15 parts per billion — was probably the result of such a situation, Barger said.

Barger added that a better indicator of lead levels is not the average of 0.12 parts per billion but instead the 90th percentile of lead levels tests, which is 2 parts per billion and is reported to the federal government and published by the water authority every year. The company tallies results of testing in ascending order and then reports the 10th highest value, he said. While the 90th percentile number is much higher than the average, it is more realistic because the average is skewed downward, Barger said.

To ensure overall water quality, the water goes through a treatment process that involved underground filtering and the addition of chlorine to kill pathogens, water authority spokesman Joan Huwiler said.

To keep lead levels low, polyphosphate material, which inhibits corrosion, is added to the water to minimize contact between the water and metal pipes, Barger said. The pH of the water is also monitored to ensure that the water will not corrode the plumbing, he said.

While the water authority has met all state and federal regulations, the water may not be as healthy as it can be. Current legal guidelines set by the Safe Water Drinking Act of 1974 are outdated inconsistent and miss many contaminants, said water expert Jonathan Borak, a Yale School of Health professor.

Borak argued that EPA regulation needs to be more systematic and consider the combined effects of chemicals. Some regulatory limits are inconsistent because they take into account some chemicals but not related chemicals that are similarly harmful, he said. Of 60,000 chemicals in use within the United States, only 91 are regulated by the Safe Drinking Water Act, which was last updated in 2005.

For example, perchlorate has been labeled by the EPA as a dangerous chemical contaminant that blocks iodine uptake in the liver, Borak said. But other chemicals in the same family, such as thiocyonate, are not as stringently regulated, he added.

“It’s as though we say a red car can speed on the highway and a blue car can’t,” Borak said.

In 2008, the South Central Connecticut Regional Water Authority tested its water for 49 unregulated chemicals and detected 11. According to their water quality report, the authority sent the results to the EPA to help the agency craft future legislation on water safety.

New Haven tap water comes from 10 lakes and three aquifers in Connecticut.