Living near a toxic waste site can be a recipe for poor health. And scientists know that the problem is widespread in developing countries where there are few cleanup programs. A pair of new studies adds a level of much-needed detail about exactly how widespread and harmful the problem can be.

One study led by the Icahn School of Medicine at Mount Sinai in New York City looked at 373 sites across India, the Philippines and Indonesia, and calculated how much damage elevated levels of lead, chromium and other chemicals imparted to human health. That work, published online in Environmental Health Perspectives on May 4, found that living near toxic sites leads to health impacts comparable to all the combined malaria issues in those three countries, or as much as the total negative impacts of air pollution.

The researchers used “disability life-adjusted years,” or DALYs, as a way to quantify the extent to which environmental toxins led to early death or illness. One DALY equals a year of healthy life lost.

“We estimate that more than eight million persons in these countries suffered disease, disability or death resulting from exposures to industrial contaminants in 2010, resulting in 828,722 DALYs,” the authors wrote. That means among the approximately 8.6 million people living near those sites, an estimated 828,722 years of healthy life were lost. Almost two thirds of the individuals living near those sites were either women of childbearing age or children.

The authors did not have direct blood-level data or biomarker information to make their calculations. Instead, they relied on environmental data for the areas surrounding the sites. For lead exposure, for example, they used lead levels in drinking water or soil, and a U.S. Environmental Protection Agency model that translates the data into projected blood lead levels. They also used World Health Organization spreadsheets “that would tell us how many people would develop cardiovascular disease or mild mental retardation from those levels,” sayslead author Kevin Chatham-Stephens, a pediatrician at The Mount Sinai Hospital who focuses on environmental health. More than 99 percent of the negative health impacts from toxic exposures were from lead or chromium, although the authors also looked at cadmium and pesticides such as DDT.

The findings still involve some unknowns and assumptions, the authors acknowledge. For example, the analysis does not take into account the synergistic or antagonistic impact of being exposed to multiple chemicals simultaneously. The authors also looked at only one major chemical contaminant per site and usually considered just one cancer and one non-cancer impact at each location, meaning their estimates may not be all-inclusive. The sites, such as former tanneries and lead battery recycling areas, were chosen from a database of toxic spots identified by the Blacksmith Institute, an international nonprofit based in New York City. Because census data is often not robust in low- and middle-income countries, the researchers also relied on analysis from investigators employed by Blacksmith to estimate population numbers with satellite imagery, government interviews and visual confirmation.

Chatham-Stephens also led the second study, which was presented May 6 at the annual Pediatric Academic Societies meeting in Washington, D.C. He and fellow researchers analyzed what lead exposure from the soil and water at toxic sites in 31 low- and middle-income countries could mean for the long-term health of infants and toddlers living in the surrounding communities.

Using population estimates and calculations about lead uptake into the blood, the team estimates that in 2010 almost 800,000 children younger than four were exposed to lead at 200 hazardous sites. At the majority of locations, which include battery recycling plants and communities where miners live and inadvertently bring home toxins on their clothing or bodies, lead levels were estimated to be high enough that they would cause elevated blood-lead levels beyond those considered safe by the U.S. Centers for Disease Control (CDC). In comparison, recent CDC estimates suggest that almost 500,000 children between the ages of one and five living in the U.S. have elevated lead levels that would prompt action.

The authors estimate that the dangerous levels of lead in these low- and middle-income countries cause a loss of five to eight IQ points across the population as well as more than 51,000 DALYs. They estimate that the exposure in these settings causes mild mental retardation in roughly six out of every 1,000 people. Those numbers sound reasonable based on the scale of the work, says Bruce Lanphear, professor of children's environmental health at Simon Fraser University in Vancouver, who is not involved with the study.

Clearly, the impact of this kind of toxic exposure is worrisome, Chatham-Stephens says. “If you lose one IQ point, it’s important to think about how much that reduces lifetime learning, and to think about its economic impact. With this data we can start to think about the economic losses at these sites and how much it costs to clean them up—and then how much you will save by cleaning up these sites and not having these exposures.” Most of these places have no waste cleanup programs, the authors note.

Although the scientific community is generally aware of the issues, “no one has tried to document these exposures in terms of what happens, and this first step is a reasonable approach,” says Kyle Steenland, an environmental health professor at Emory University’s Rollins School of Public Health who studies occupational lead exposure. He cautioned that because the studies rely so heavily on estimates, the data must be considered as just a first attempt to quantify the issue. “There is a large amount of uncertainty at each step here.”