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Study finds fault with lead-testing technique

By examining deeper soil, researchers found past methods for measuring lead to be inaccurate

More soil lead contamination exists in Rhode Island than previously recorded by state lead examiners, according to a recent study by University researchers.

The study examined the lead-testing methods of the Rhode Island Department of Health and found previous methods literally did not dig deep enough — only examining surface soil samples when lead may be found deeper in the soil.

One source of lead contamination is paint coating water towers painted decades ago. The paint chips off, falls to the soil and is blown around by the wind.

When one such tower was replaced in 2003, contractors inspecting the site found areas surrounding the tower had soil containing lead by Rhode Island Department of Environmental Management standards, according to the study. Residents nearby were disgusted by the discovery of lead and hired their own contractors to determine just how much of the nearby soil was hazardous, using Rhode Island Department of Health standards instead.

Spurred to action, the state health department requested the Brown University Superfund Research Program look into the department’s standards for examining soil for lead. The researches found because the department only looked at surface soil samples, they missed the presence of lead lurking beneath the top layer and underestimated the level of contamination.

Soil samples from 31 properties were analyzed for lead concentrations. Four locations — comprising 13 percent of properties examined — were labeled “soil lead hazard,” according to the study.

The researchers took samples from the surface of the soil along with samples from both six inches and 12 inches below the surface, said Marcella Thompson, postdoctoral research associate in pathology and laboratory medicine, and the lead author of the study.

The researchers found certain properties to be misclassified in terms of their lead hazard. These locations were falsely classified because only the surface of these properties had been examined for lead, Thompson said.

Lead contained in deeper levels of soil can still serve as a source of exposure for humans. “If you’re thinking about planting a garden, lead can be taken by the plants,” said Kim Boekelheide, professor of medical science, pathology and laboratory medicine and an author of the study. Children also risk exposure when they play in contaminated dirt, he added.

According to Rhode Island Department of Health standards, lead­-free soil refers to soil with less than 150 milligrams of lead per kilogram of soil, as noted in the study. This can be confusing, especially to residents with no scientific background, Thompson said.

“The use of the terminology ‘lead­-free’ was not really lead free,” Thompson added.

After the study highlighted faults in the state health department’s lead testing techniques, the department has committed to tweaking standards, Thompson said.

“I’m very pleased to think that the Rhode Island Department of Health cared enough about the quality of their work that they have that philosophy of continuous improvement,” Thompson said.

But there is still work to do in examining lead contamination. “The next steps are up to (the state departments of health and environmental management) in terms of how they want to monitor further potential exposures” and pinpoint other locations where the lead may have been distributed, Boekelheide said.


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