To find chronic lead exposure, map out the risk

"As we move forward into an age when acute lead poisoning is rare, we need better tools to monitor for chronic, long-term exposure to lead," says Samantha Distler. (Credit: Getty Images)

A more precise screening index could monitor chronic lead exposure, say researchers.

Chronic exposure still occurs in some communities that limited screening programs for children’s blood lead levels may miss. The more precise screening index, illustrated with a map, provides a fine-grain view of areas where children are most at risk for low-level lead exposure in the city of Atlanta and throughout the state of Georgia.

Scientific Reports has published their new method, including analyses that tested and showed its efficacy, using historical data.

The new screening index is based on established risk factors for lead exposure, including poverty and housing built before 1950. The index pinpointed 18 highest-priority census tracts in metro Atlanta, encompassing 2,715 children under the age of six—or 1.7% of all children that age in greater Atlanta.

These highest-priority areas include the historically Black neighborhoods of English Avenue and Vine City, where Emory University researchers had previously identified elevated levels of lead in the soil of some yards and vacant lots.

“As we move forward into an age when acute lead poisoning is rare, we need better tools to monitor for chronic, long-term exposure to lead,” says first author and Emory graduate Samantha Distler. “We developed an interactive map that can be used by physicians and other health officials, and even by individuals who want to check their own children’s risk levels. You can easily zoom in to find an exact location, so there’s less guess work involved in assessing what is a high-risk area.”

The method could be applied to any area in the United States, she adds.

Lead exposure and children’s brains

“Lead is a toxicant that is particularly dangerous to children and their developing brains,” says Dister, who led the work as an undergraduate. She is now a graduate student of epidemiology at the University of Michigan School of Public Health.

“Even low blood lead levels are associated with neurological deficits in children,” she says.

“One of the biggest problems concerning lead is that many people don’t know if their children are being exposed,” says Eri Saikawa, senior author of the study and associate professor in Emory’s department of environmental sciences and Rollins School of Public Health. “Detecting lead exposure as early as possible is very important so preventative measures can be taken. The easiest way to do that is to screen the blood.”

In addition to neurological deficits, lead exposure is associated with immunological and endocrine effects and cardiovascular disease. Decades ago, federal regulations reduced lead in paint and gasoline and other common exposure sources. The resulting drop in children’s blood lead levels in the United States is considered one of the greatest public health achievements in the country’s history.

Many people remain unaware, however, that lead persists in the environment. “It can linger for a really long time in everything from soil to water,” Distler says. “That puts some people at risk for chronic exposures to low levels over a long time.”

Poverty, blood tests, and ZIP code

The Centers for Disease Control and Prevention (CDC) estimates that at least four million households in the United States have children living in them who are being exposed to high levels of lead. And about half a million of those children aged one to five years have blood lead levels above five micrograms per deciliter, the level at which the CDC recommends initiating public health action.

Despite this alarming statistic, many children in higher-risk areas are not screened for blood lead levels. In Georgia, data from the period 2011 to 2018 show that the proportion in various ZIP code tabulation areas who have been tested range from 1% to 67%, with a median of 13%.

The researchers realized that one problem may be that health officials focus screening efforts on a county-wide basis, rather than zeroing in on the highest-risk neighborhoods within those counties.

In 2009, a team led by researchers at the CDC developed and published a priority screen index for Atlanta neighborhoods based on housing age and percentage of residents enrolled in Georgia’s Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), a proxy for poverty.

For the current paper, the researchers built on the efforts of the 2009 paper, drilling down from neighborhoods to more precise US Census Bureau tracts. Data from the American Community Survey was used to assess the relative level of poverty and proportion of homes built before 1950.

They applied a priority screening index, ranging from two to eight, to the census tracts. The areas of highest relative poverty and proportion of homes built before 1950 received the highest score. The researchers applied this index to census tracts across the state of Georgia and to the entire United States to identify tracts that consistently have the highest priority screening index values.

“The visualizations of our priority screening index that we’ve created using interactive maps can empower physicians and health officials to better target children at high risk for lead exposure,” Distler says. “We hope our work will help lead to improved policies and actions to reach children who are most at risk for lead exposure and to improve their lives—not just in Georgia but throughout the United States.”

Source: Emory University