Shocking new study finds 25% of US shipyards have dangerous lead levels

Nearly 40% of households may exceed safety recommendations due to multiple sources of lead exposure. Nationally, applying standard remediation techniques to address this problem could exceed costs of $1 trillion.

A new study finds that about one in four American homes have floor lead levels above the U.S. Environmental Protection Agency’s updated screening threshold of 200 parts per million (ppm), or one reduction from the previous limit of 400 ppm. Additionally, for households facing exposure from multiple sources, the EPA further reduced the guideline to 100 ppm; the study found that almost 40% of households exceed this stricter level.

“I was shocked to see how many households exceeded the new limit of 200 ppm,” said Gabriel Filippelli, a biochemist at Indiana University who led the new study. “I thought it would be a more modest number. And the results for the 100 ppm guideline are even worse.

Remediating the estimated 29 million affected households using traditional “dig and dump” soil removal methods could cost more than $1 trillion, according to the study’s calculations. The study was published in GeoHealth, an open access AGU journal that publishes research on the intersection of human and planetary health for a sustainable future. Filippelli is the former editor-in-chief of GeoHealth.

National lead problem ‘far from solved’

Lead is a heavy metal that can accumulate in the human body and cause toxic effects. In children, lead exposure is associated with poor academic performance. In the United States, the burden of lead exposure has historically fallen on low-income communities and communities of color due to redlining and other discriminatory practices. Lead pollution can come from aging water pipes, old paint, leftover gasoline, and industrial pollution, but today most lead exposure comes from soil and dust contaminated, even after the removal of infrastructure containing lead.

The Centers for Disease Control and Prevention (CDC) first set a blood lead concentration limit in 1991 at 10 micrograms per deciliter, and lowered this limit several times until reaching the current limit of 3 .5 micrograms per deciliter. But the EPA’s soil lead testing level remained unchanged for more than 30 years until the January announcement. Some states had already established their own lower guidelines; California has the lowest testing level, at 80 ppm.

This discrepancy is probably due to “the immensity and omnipresence of the problem,” write the authors of the study. “The scale is staggering, and the country’s leadership and remediation efforts have become much more complicated.” That’s because once the EPA lowers a screening limit, it has to tell people what to do if their soils exceed it.

When the EPA lowered the level of testing, Filippelli and his co-authors decided to use the database of 15,595 residential soil samples from the contiguous United States that they had collected over the years to discover how many exceeded the new guidelines.

Household health risk

About 25% of residential soil samples, collected from yards, gardens, alleys and other residential locations, exceeded the new level of 200 ppm, according to the study. (Only 12% of samples exceeded the old level of 400 ppm.) Extrapolating to the entire country, that equates to about 29 million homes.

The EPA issued separate guidelines for households with multiple sources of exposure, such as contaminated lead soils and pipes, setting the level in those situations at 100 ppm. In practice, this is the case for most urban households, Filippelli said. Forty percent of households exceed this limit, bringing the number of affected households to almost 50 million, according to the study.

Typically, contaminated soils are remediated by removal – colloquially, “dig and dump.” But the practice is costly and is typically only used after an area has been placed on the national sanitation priority list, a process that can take years. Remediating all contaminated homes by “dig and dump” would cost between $290 billion and $1.2 trillion, the authors calculated.

A less expensive option is to “cover”: bury the contaminated soil with about 30 cm of soil or mulch. A geotechnical fabric barrier can also be installed. Most lead contamination is in the top 10 to 12 inches of soil, Filippelli said, so this simple method masks the problem or dilutes it to an acceptable level.

“Urban gardeners have been doing this forever anyway, with raised beds, because they are intuitively concerned about the land use history in their home,” Filippelli said.

And capping is faster.

“A huge advantage of capping is speed. This immediately reduces exposure,” Filippelli said. “You don’t wait two years on a list to clean up your yard while your child is being poisoned. It was done in a weekend.»

Corking still requires time and effort; residents must find clean soil, carry it to their homes and spread it. But the health benefits likely outweigh those costs, Filippelli said.

Because capping was done more informally, there is still much to learn about its lifespan and durability, Filippelli said. This is where the research will then head.

Despite the “staggering” scale of the problem, “I’m really optimistic,” Filippelli said. “Lead is the most easily solvable problem we have. We know where it is and how to avoid it. It’s just about taking action. »

Reference: “One in four U.S. households likely to exceed new guideline levels for lead in soil” by Gabriel M. Filippelli, Matthew Dietrich, John Shukle, Leah Wood, Andrew Margenot, S. Perl Egendorf, and Howard W. Mielke , June 18, 2024, GeoHealth.
DOI: 10.1029/2024GH001045