Lake Norman High School in Mooresville is using bottled water this week after tests of the school’s drinking water supply found a chemical that’s manufactured for use in rocket propellant and fireworks.
The chemical in question, perchlorate, may affect the thyroid in people exposed to it for a long time, a federal agency says. Its discovery at the school coincides with a state investigation of higher-than-normal cases of thyroid cancer in southern Iredell County, including Mooresville.
It’s unclear whether the two incidents are related. The Iredell-Statesville Schools are retesting Lake Norman High’s water to learn whether the initial results were flawed. And 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.
The Iredell-Statesville Schools board voted Monday, as a precaution, to provide bottled water at Lake Norman High as the school’s water is retested this week. A municipal water line serving the school also supplies six other schools where elevated perchlorate was not found, and district officials suspect the high school’s results were flawed.
The district decided last summer to test its drinking water, in part because of an uproar over lead found in water at some Charlotte-Mecklenburg schools, Iredell-Statesville communications director Boen Nutting said Wednesday. 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.
Lake Norman High’s water was retested Tuesday and again Wednesday, Nutting said, but results have not yet been returned.
“Friday is our last day (before Christmas), so that will give us time to get then results and then have a plan,” she said. “We want to work with everybody. We want the best for our community.”
North Carolina health officials said in June that they will investigate an unusual number of thyroid cancer cases that have been detected in two ZIP codes in southern Iredell County.
State and local officials have held weekly meetings while that study is underway, the N.C. Department of Health and Human Services spokesman Cobey Culton said this week.
Thyroid cancer rates rose across the U.S. between 1999 and 2015, for unknown reasons, Iredell County officials said in a statement Tuesday. Radiation treatments to the head or neck during childhood can increase risks, the county said, but state health officials have not identified any environmental causes.
In North Carolina, the thyroid cancer rate tripled between the mid-1990s and 2016, the statement said. In southeastern Iredell County during that time, it said, the rate increased from 7.5 cases per 100,000 people to 23.7 cases. In southwestern Iredell, where Lake Norman High is located, the rate went from 4.1 cases in the 1990s to 34.6 cases by 2016.
“While the state has not completed its investigation or determined whether this should be defined as a cancer cluster, it is important to know that we share the community’s concerns and are actively engaged in trying to understand and respond to higher rates of thyroid cancer in southern Iredell County,” the statement said. “Regardless of how the increase in thyroid cancer is defined, the maximum available resources are being made available for this investigation.”
The state health department and Department of Environmental Quality is assessing whether environmental contaminants are linked to the cancer cases, the county said, and is working with hospitals and physicians to make sure all thyroid cancer cases are reported to the state. A team of Duke University researchers is also investigating, it said.