Study finds possible link between stroke rates, refinery pollutants

Residential exposure to pollutants emitted by petroleum refineries could be related to the prevalence of stroke rates across the southern United States, a new study has found.

Living near petroleum production sites and refineries was potentially linked to 5.6 percent of strokes among adults surveyed in seven states across the region, according to the study, published on Thursday in Environmental Research Letters.

The process of refining petroleum, a common industry in the U.S. South, releases multiple pollutants that researchers have previously connected to strokes.

But the authors of the new study sought to identify the direct relationship between residential exposure to petroleum refining and the development of strokes.

“The geographic concentration of economic sectors, and their associated by-products, is an underexplored, plausible risk factor for stroke,” lead author Honghyok Kim, who will be joining the University of Illinois at Chicago as an assistant professor this month, said in a statement. 

“By-products of petroleum production and refining include a mixture of pollutants that may impact the quality of adjacent air, soil, and potable water in residential areas,” Kim added.

To draw their conclusions, Kim and his colleagues at Yale, Brown and Seoul National universities combed through data from the Centers for Disease Control and Prevention’s Population Level Analyses and Community Estimates for seven Southern U.S. states.

They narrowed down the data to areas within 2.5 kilometers (1.6 miles) or 5 kilometers (3.1 miles) of petroleum refineries — zones strongly correlated with high levels of sulfur dioxide, a byproduct of the refining process.

Across these areas, the authors observed that the prevalence of self-reported stroke ranged from 0.4 percent to 12.7 percent, while people of lower socioeconomic status and of Hispanic ethnicity tended to reside closer to the refineries.

After analyzing the data, the scientists concluded that the percentage of strokes potentially explained by residential exposure to petroleum refineries was about 5.6 percent — a total of 2,200 cases.

The results differed by state, with Mississippi showing the highest percentage — 11.7 percent — of strokes possibly linked to such exposure, according to the study.

Zooming in much more locally, the scientists found even more dramatic variations in results based on census tract. One tract in Texas showed the highest prevalence of strokes potentially explained by petroleum refineries, at 25.3 percent, according to the study. 

The authors also emphasized their observation that sociodemographic factors influenced the prevalence of strokes in each region, noting that those individuals of lower socioeconomic status were disproportionately affected.

This association with sociodemographic factors, they added, could “be relevant to understanding and addressing entrenched sociodemographic disparities in stroke outcomes.”