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PM2.5 is Linked to Increased Hospitalization Risk in Seniors

A recent study led by Harvard T.H. Chan School of Public Health suggests that prolonged exposure to fine particulate air pollutants (PM2.5) could heighten the likelihood of seniors being hospitalized for various cardiovascular ailments.

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The Environmental Protection Agency (EPA) revealed on February 7 its revised National Ambient Air Quality Standards, reducing the allowable average annual PM2.5 concentration in the United States from 12 micrograms per cubic meter (μg/m3) to 9 μg/m3.

The study was published online in The BMJ on February 21st, 2024.

The researchers analyzed hospital records and PM2.5 exposure data for nearly 60 million Medicare recipients aged 65 and above, spanning the years 2000 to 2016. Utilizing various air pollution datasets, they constructed a predictive map illustrating PM2.5 concentrations across the contiguous United States and correlated this with the beneficiaries' residential ZIP codes.

Over the study period, they tracked each beneficiary annually until their initial hospitalization for one of seven primary subtypes of cardiovascular disease (CVD): ischemic heart disease, cerebrovascular disease, heart failure, cardiomyopathy, arrhythmia, and thoracic and abdominal aortic aneurysms. Additionally, they assessed the risk of first admission for a composite of these CVD subtypes.

According to the study's findings, a three-year average exposure to PM2.5 was linked to a heightened risk of initial hospitalization for all cardiovascular conditions, with notable associations observed for ischemic heart disease, cerebrovascular disease, heart failure, and arrhythmia.

The study revealed that for composite cardiovascular disease (CVD), when seniors were exposed to chronic PM2.5 levels ranging between 7 and 8 μg/m3, mirroring the current national average, the average annual risk of hospitalization for CVD was 3.04%.

In contrast, when PM2.5 exposure complied with the WHO guideline of below 5 μg/m3, the average annual risk of hospitalization for CVD decreased to 2.59%. Based on these figures, researchers estimated that lowering the annual average PM2.5 levels from 7-8 μg/m3 to below 5 μg/m3 could potentially reduce overall cardiovascular hospitalizations by 15%.

Despite the noted improvement, the researchers emphasize that the results imply there is no safe threshold for chronic exposure to PM2.5 concerning overall cardiovascular health. They underscore that the health hazards associated with prolonged PM2.5 exposure remain significant for at least three years.

Moreover, they highlight that these risks disproportionately affect individuals with lower educational attainment, limited healthcare access, and those residing in socioeconomically disadvantaged areas.

Stronger efforts are urgently needed to improve air quality and thereby alleviate the burden of cardiovascular disease—a leading cause of death and a major contributor to health care costs. Our findings indicate that the EPA’s newly updated PM2.5 standard is clearly insufficient for the protection of public health.

Joel Schwartz, Study Senior Author and Professor, Environmental Epidemiology, Harvard T.H. Chan School of Public Health

Other authors from Harvard Chan School involved in the study were Yijing Feng, Mahdieh Danesh Yazdi, Edgar Castro, Alexandra Shtein, Xinye Qiu, Adjani Peralta, Brent Coull, and Francesca Dominici.

Funding for the research was provided by the National Institutes of Health through grants R01ES032418, R01MD012769, R01ES028033, R01AG060232, R01ES030616, R01AG066793, R01MD016054, and P30ES000002, as well as support from the Alfred P. Sloan Foundation through grant G-2020-13946.

Journal Reference:

Wei, Y., et al. (2024) Exposure-response associations between chronic exposure to fine particulate matter and risks of hospital admission for major cardiovascular diseases: population based cohort study. The BMJ.


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