American Indian communities benefit less from downward trends in air pollution: study

Declines in pollution levels from a pervasive air contaminant have been much weaker in counties where American Indian communities reside, a new study has found.

Exposure to fine particulate matter, also known as PM2.5 – particles with a diameter of 2.5 microns or less – can have both short-term respiratory impacts and long-term effects on lung function, increasing the risk of cardiovascular and respiratory disease.

And while concentrations of these dangerous particles are dropping in counties that lack American Indian populations, the same trend does not apply to counties where such communities live, according to new research published in the American Journal of Public Health.

“Our results underscore the need to strengthen air pollution regulations and prevention implementation in tribal territories and areas where [American Indian] populations live, ”Maggie Li, first author of the study and a PhD candidate at Columbia University’s Mailman School of Public Health, said in a statement.

To draw their conclusions, the scientists compared ambient average concentrations of PM2.5 – the amount of PM2.5 in an air sample – in counties with American Indian populations and those without, in the contiguous US from 2000 to 2018. They used a combination of prediction models and monitoring sites when available to estimate the difference in countywide annual concentrations during this period.

The authors said they chose to conduct their analysis at the county level, as this unit tends to inform regulatory action. They then cross-referenced the air pollution information with population data and household income from the 2010 US Census, according to the report.

In the year 2000 – the first year included in the study – average modeled PM2.5 concentrations in counties where Native Americans live were 1.46 micrograms per cubic meter lower than those in counties where they do not reside.

But the authors found that at the end of the study period, the tables had turned.

By 2018, the levels of PM2.5 were 0.66 micrograms per cubic meter higher counties with American Indian populations than in those without, according to the report.

Of the 199 US counties classified as American Indian-populated, about 82 percent were rural, and of the 2,909 counties classified as non-American Indian populated, about 61 percent were rural.

The gap between average PM2.5 concentrations – which were still below the Environmental Protection Agency threshold of 12 micrograms per cubic meter – in the two types of counties decreased over time, until the situation flipped in 2015, the authors found.

But because exposure to PM2.5 is a “risk factor for cardiovascular disorders and other adverse health outcomes even at levels below the current national ambient air quality standards,” the authors stressed the importance of continuing to characterize exposure patterns – particular in areas where socioeconomically disadvantaged populations reside.

“The history of US settler colonialism has contributed to the displacement of tribes and forced acculturation of Native children to Western educational and sociocultural systems,” they stated. “These factors have exacerbated levels of poverty, poor health, and chronic diseases in this population.”

Cardiovascular disease is the leading cause of death in Native American populations, occurring at significantly higher rates in these communities than in white populations, according to the authors.

Ana Navas-Acien, a senior co-author and professor of environmental health sciences at the Columbia Mailman School, described “a critical need for future investigations” of the health effects linked to air pollution in American Indian populations. She also called for interventions that “ensure the observed inequalities can be eliminated.”

Marianthi-Anna Kioumourtzoglou, senior co-author and an assistant professor of environmental health sciences at the Columbia Mailman School, said their findings build upon existing studies that demonstrate how disadvantaged communities endure “disproportionate burdens of environmental hazards.”

“Native Americans may be particularly susceptible to the adverse health effects of PM2.5 and air pollution, but research quantifying air pollution exposures and impacts on health among this population is lacking,” Kioumourtzoglou said in a statement.

“These communities already face a large disease burden attributable to environmental pollution due, for instance, to extensive mining and water contamination on Tribal Lands,” she added.

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