Retests of drinking water at Mooresville’s Lake Norman High School found none of the chemical used in rocket propellant that had caused alarm last week, the school district said Thursday.
Iredell-Statesville Schools had supplied bottled water to the school after perchlorate, which can affect the thyroid, was found in water from one faucet. The unexpected finding rattled district officials and parents because the area is also the subject of studies of higher-than-normal occurrence of thyroid cancer.
Water from the suspect faucet was retested twice last week, and two additional faucets at the school were tested. Those tests didn’t detect perchlorate, the district said.
“The first reading at LNHS was really a puzzle to everyone,” Kenny Miller, assistant superintendent of facilities and planning, said in a statement Thursday. “We couldn’t figure out how one faucet out of all of our 36 sites would test so high for perchlorates.”
No perchlorate had been detected in water samples taken at Lakeshore Elementary and Lakeshore Middle schools, which use the same water line that supplies Lake Norman High, Miller added.
The retests indicate that the initial water sample from Lake Norman High was accidentally contaminated, the district said. It has asked its consultant, Reliant Environmental, how and where that could have occurred.
Perchlorate is manufactured for use in products including rocket propellant and fireworks. While long-term exposure to perchlorate causes cancer in lab rats, the Agency for Toxic Substances and Disease Registry says it’s not considered likely to do so in humans.
North Carolina does not regulate the chemical in drinking water, and federal authorities are reviewing whether safety standards limiting perchlorate in water are justified.
Iredell-Statesville Schools had decided to test water at its schools in part because of controversy over lead found in water at some Charlotte-Mecklenburg schools. A toxicologist suggested that the tests include perchlorate, which would not normally be part of them, because of the thyroid cancer issue and because some states outside North Carolina regulate the chemical in water.
Thyroid issues in southern Iredell County are of concern because an unusual number of thyroid cancer cases have been detected in two ZIP codes there, including Mooresville. State health officials are investigating.