‘No safe threshold’: Air pollution increases risk for hospitalization among older adults

Key takeaways:

• Exposure between 9 and 10 g/m³ was associated with a 3.35% risk for CVD hospitalization.
• There is “no safe threshold” for the chronic effect of air pollution on overall cardiovascular health, researchers said.

Chronic exposure to fine particulate matter increased the risk of hospitalization for several cardiovascular conditions in older adults, according to a study published in BMJ.

“Our research shows that low-level exposure to [particulate matter (PM_2.5)] presents a substantial risk to cardiovascular health, even at levels below the newly released [U.S. Environmental Protection Agency’s (EPA)] national standard of 9 g/m³,” Yaguang Wei, PhD, a research associate at Harvard T.H. Chan School of Public Health, told Healio. “The current national average for annual PM_2.5 is between 7 µg/m³ and 8 µg/m³; if we were able to reduce this below 5 µg/m³, the WHO air quality guideline published 3 years ago, we could prevent 15% of cardiovascular hospitalizations.”

On Feb. 7, the EPA announced it had changed its National Ambient Air Quality standards, setting the level of the primary health-based annual PM_2.5 standard from 12 g/m³ to 9 g/m³.

In the study, the researchers examined hospital records and PM_2.5 exposure levels of Medicare fee-for-service beneficiaries (n = 59,761,494) between 2000 and 2016.

Overall, 3-year average exposure to PM_2.5 was associated with increased RRs for hospitalization for all cardiovascular conditions, which included:

• cardiomyopathy;
• heart failure;
• ischemic heart disease;
• arrhythmia;
• cerebrovascular disease; and
• thoracic and abdominal aortic aneurysm.

The researchers found that for composite CVD, the risk for hospitalization increased 1.29 (95% CI, 1.28-1.3) times at exposures between 9 and 10 g/m³ when compared with exposures between 0 to 5 g/m³.

Meanwhile, on an absolute scale, the risk for hospitalization for CVD rose from 2.59% with exposure of 5 g/m³ or less to 3.35% with exposure between 9 and 10 g/m³.

Ultimately, the results suggest “that no safe threshold exists for overall cardiovascular health,” the researchers wrote, although they “were crucial for informing targeted interventions to specifically mitigate the adverse impacts of PM_2.5 on these conditions.”

Wei added that the study “reveals that people with lower educational levels, limited health care access, and residents of deprived areas face a higher risk of cardiovascular issues due to PM_2.5 exposure.”

“Primary care physicians should particularly focus on these groups, advising them to monitor local air quality, wear masks during poor air conditions, and use air purifiers indoors,” he said.

References:

• Chronic exposure to air pollution may increase risk of cardiovascular hospitalization among seniors. https://www.hsph.harvard.edu/news/press-releases/chronic-exposure-to-air-pollution-may-increase-risk-of-cardiovascular-hospitalization-among-seniors/. Published Feb. 21, 2024. Accessed Feb. 21, 2024.
• Final reconsideration of the national ambient air quality standards for particulate matter (PM). https://www.epa.gov/pm-pollution/final-reconsideration-national-ambient-air-quality-standards-particulate-matter-pm. Published Feb. 7, 2024. Accessed Feb. 20, 2024.
• Wei Y, et al. BMJ. 2024;doi:10.1136/bmj-2023-076939.