Babies in North Carolina are more likely to have heart defects if their mothers drank water from wells that are high in manganese, a heavy metal.
Using six years' worth of the state's childbirth records and data about drinking water wells, UNC-Chapel Hill and state researchers found the connection between the defects and manganese-rich wells.
Water wells throughout the center of the state, including parts of the Triangle, are saturated with manganese, they found.
In recent years, health researchers have turned their attention to heavy metals—such as cadmium, mercury, chromium and arsenic—particularly for their effects on unborn children.
UNC-Chapel Hill professor Rebecca Fry and others have shown that cadmium can accumulate in mothers' blood and potentially harm newborns' health.
So it's not entirely novel that a metal has been implicated in a health problem. But what is new, according to Fry, is that researchers have turned to data-rich maps to make these findings.
"Just being able to map those metals across the state is very new," said Fry, whose expertise is in the health effects of heavy metals.
The researchers gathered data about 20,000 babies born with birth defects, as documented by the N.C. Department of Health and Human Services' Birth Defects Monitoring Program. As a control, they also considered about 668,000 born without defects.
The babies were born throughout the state, which meant that the babies' mothers lived in counties where water quality can vary dramatically from well to well.
The researchers wanted to know whether well water was related to the newborns' birth defects. But they were limited, Fry said, since they couldn't measure the mothers' actual water consumption.
"We don't have active environmental monitoring in everyone's home," she said.
To estimate the water that the mothers drank, the researchers instead relied on geocoding, a technique that allows different types of data to be plotted on maps.
It's a technique that's gaining momentum in public health research, according to Tzy-Mey May Kuo, a research associate at UNC's Lineberger Comprehensive Cancer Center.
Using state records about well water, the researchers mapped out the varying quality of the water across the state. They then combined this water data and another key data set—the locations of mothers' homes while they were pregnant—in order to predict, on average, what heavy metals were entering the women's bodies and potentially the bodies of their unborn children.
This complex method allowed them to answer three simpler questions: Where in the state is well water a problem, where are children being born with defects and is there a connection between the two?
When the data crunching was done, the situation was clear.
Manganese is highly concentrated in many North Carolina wells, the researchers found, especially in the central counties of the state, which sit above the Carolina slate belt, a cross-state geologic formation with an abundance of manganese. In fact, about 20 percent of private water wells exceeded the EPA's suggested limit for the metal.
And the manganese appeared to be causing harm. Newborns had a higher chance of being born with heart defects if their mothers drank the manganese-rich water, the study found.
Manganese toxicity follows a basic principle: the dose makes the poison. The body needs a small amount of the metal to function properly. But excessive amounts can be harmful.
Health researchers have known since the 1800s that manganese, which is used to harden steel, can cause neurological disorders in humans who've had high enough doses. Its effects, in fact, can emulate those of Parkinson's disease. Among children, it's also suspected of causing problems with neurological development.
But while their finding is worrisome, the researchers admit that their study had several significant limitations.
Though their sample size was large, the researchers were hampered by a lack of data about the mothers' actual water consumption.
The researchers say the lack of individual measurements points to the need for biomonitoring, or chemical measurements of study participants' bodies. But North Carolina doesn't have any biomonitoring programs for pregnant women.
They also note that until 2008 state government did not require residents to test well water. And even then, the tests were only made mandatory for new wells. So while the study relied on data from 1998 to 2010, the pre-2008 data would have come from residents who chose to have their wells tested. And that could have biased the data, the researchers say.
Federal and state regulations don't cover the quality of well water, so residents concerned about their water can contact their county health department, which offers tests of private water wells, including those for a number of heavy metals such as manganese. The cost of the tests varies, depending on the county. Montgomery County, for example, charges $35-$85.
Residents can also install technology to remove heavy metals. But those filters can be more expensive—$300-$500—than conventional water filters.
DHHS also collects water samples from newly drilled wells and provides a list of contaminants, possible remedies for such contaminants, as well as any health risks associated with consuming the water. DHHS recommends that new well owners sample their well annually.
This story originally appeared in N.C. Health News, a nonprofit journalism organization based in the Triangle. See maps related to this story on the NCHN site at www.northcarolinahealthnews.org.
This article appeared in print with the headline "Mapping metal"