Research identifies hierarchy of demographic, housing traits most likely to host high soil lead levels
by Lauren Milideo, UVM An estimated 25-40% of homes in the U.S. have soil contaminated with lead, a toxic heavy metal that can harm children’s development. Public health researchers know that the risk is higher in places with a legacy of industrial manufacturing, but drilling down into what parts of a community are likely to see lead soil contamination has posed a challenge to researchers.
A new study published on June 15 in the journal Geohealth by UVM researchers lays out a new, fairly straightforward method for pinpointing pollution. When tested, the scientists found that patterns of soil lead contamination in two Northeastern cities, Springfield, Massachusetts, and Hartford, Connecticut, closely mirrored neighborhood demographics, with income, housing type, age, and race emerging as key predictors.
Lead author and Gund Institute affiliate Nico Perdrial says knowing which features are tied to contamination could help residents and municipalities identify where best to deploy lead testing and mitigation measures.
“Some groups are much more likely to live in highly lead-contaminated soils,” says Perdrial, a professor in the College of Arts and Sciences. This was particularly true in Hartford, whose soils were more lead-contaminated overall than Springfield’s. In Hartford, the population most likely to be exposed to soil lead contamination were children of color living in multifamily housing.
The researchers tested about 300 soil samples for lead contamination, half from each city. They chose cities that shared a similar industrial history and were geographically close to each other, allowing straightforward comparison, and focused on residential areas, Perdrial says, because “this is where children play.” They then fed their results into a model, along with other parameters of each sample’s location, using publicly available census and tax data. These included housing type (i.e. multifamily or single-family); residents’ racial data; ages and numbers of children present; and residential tax values.
A more detailed look
The new modeling approach allowed the researchers to parse out specifically which demographic and historical factors were driving lead exposure.
“In Hartford, we see that populations that typically live in single-family housing of higher value, in blocks that have lower-than-average Hispanic populations, have a lot less chance of being affected by, or being in contact with, soil lead,” Perdrial says. “That creates a dichotomy in the city of Hartford.”
In Springfield, neighborhoods whose populations of white, non-Hispanic residents were lower than the city’s average, had a 1.7 times higher chance of having elevated lead soil levels. And within these areas, locations with multifamily housing, and more children than the average city population, had a 2.4 times increased likelihood of high soil lead.
For Hartford, the team also placed their findings in the context of the city’s history of redlining, a racist 20th-century mortgage-lending practice that made desirable urban housing available only to white families while forcing residents of color into crowded, less-desirable parcels often impacted by highway traffic, industrial activity, and the associated environmental pollution concentrated in such neighborhoods.
“Redlining drove lead exposure much more than any other parameter we measured,” Perdrial says.
Corresponding historical redlining data were not available for Springfield, Perdrial says, but “in Hartford, neighborhoods that were considered ‘desirable’ were less than half as likely to have high lead soil levels.” Those neighborhoods rated least desirable on historic Home Owners’ Loan Corporation maps were 20% likelier to have high lead soil levels, and within those neighborhoods, soil surrounding multifamily homes was 40% more likely to have high lead readings.
“It's an indication that a legacy of environmental racism exists in the soil,” Perdrial says. “It's not just the contaminant that is a legacy. The soil has this memory that we cannot just eliminate by changing policies.”
Now, the researchers are encouraging colleagues in their field to expand the work to other cities with industrial pasts. The researchers’ statistical methods in this study were novel, but possible to replicate, Perdrial says. And understanding where soils are most likely to be lead-contaminated can aid in efforts to prevent or ameliorate its detrimental effects on residents, particularly children.
“There is often a tendency to believe that lead is an issue of the past because lead paint and leaded gasoline were banned years ago,” Perdrial says. “But in fact, we're showing that there is a lasting memory in the cities. It's invisible but embedded in our society.”
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