The study demonstrates a connection between hospitalisation risk for serious heart and lung problems and exposure to fine particulate matter. The worldwide Burden of Disease research estimates that exposure to PM2.5 is responsible for 4.2% of the world’s disability-adjusted life years (a measure of years lived in good health) and 7.6% of all worldwide mortality.
The World Health Organisation (WHO) revised the air quality standards in 2021 in light of this substantial data, advising that 24-hour average PM2.5 levels should not exceed 15 mg/m3 on more than 3–4 days year and that annual average PM2.5 levels should not exceed 5 mg/m3.
In the first study, conducted between 2000 and 2016, researchers connected residence zip codes with average daily PM2.5 levels for roughly 60 million US people (of whom 55% were women and 84% were white) who were 65 years of age or older. They then tracked hospital admissions for an average of eight years using Medicare insurance data.
Average three-year exposure to PM2.5 was linked to higher odds of initial hospital admissions for seven major types of cardiovascular disease: ischemic heart disease, cerebrovascular disease, heart failure, cardiomyopathy, arrhythmia, valvular heart disease, and thoracic and abdominal aortic aneurysms. This association persisted even after controlling for a variety of economic, health, and social factors.
Exposures between 9 and 10 mg/m3, which included the US national average of 9.7 mg/m3 during the study period, were linked to a 29% increased risk of hospital admission for cardiovascular disease when compared with exposures of 5 mg/m3 or less (the WHO air quality guideline for annual PM2.5).
When exposures were between 9 and 10 mg/m3, the probability of hospital admission for cardiovascular disease rose from 2.59% with exposures of 5 mg/m3 or less to 3.35% overall. “This means that if we were able to manage to reduce annual PM2.5 below 5 ug/m3, we could avoid 23 per cent in hospital admissions for cardiovascular disease,” according to the investigators.
Following exposure to PM2.5, these cardiovascular effects lasted for at least three years, and susceptibility differed according to factors including age, education, access to healthcare, and degree of neighbourhood deprivation.
According to the researchers, following the WHO air quality standard might have a significant positive impact on cardiovascular health overall and there may not be a safe threshold for the long-term effects of PM2.5.
“The US Environmental Protection Agency (EPA) revised the national air quality guideline for annual PM2.5 level on February 7, 2024, placing a more stringent cap of no more than 9 ug/m3. The last update since 2012 is this one. It is still far greater than the WHO’s threshold of 5 ug/m3, though. * They also state that the recently released national norm was insufficient to safeguard the public’s health.
In the second study, hospital admissions and ER visits for respiratory, cardiovascular, and natural causes were tracked for 50 million US people aged 18 and older from 2010 to 2016. Researchers analysed county-level daily PM2.5 concentrations and medical claims data.
Over 10 million hospital admissions and 24 million ER visits were documented over the research period. They discovered that there was a statistically significant correlation between short-term exposure to PM2.5 and higher rates of hospital admissions for natural causes, cardiovascular disease, respiratory disease, and emergency department visits for respiratory disease—even at concentrations below the new WHO air quality guideline limit.
In instances when the daily PM2.5 levels were below the recently established WHO air quality guideline limit of 15 mg/m3, for instance, a daily rise in PM2.5 of 10 mg/m3 was linked to 1.87 more hospital admissions per million persons aged 18 +. According to the researchers, these results significantly advance the discussion around the reform of air quality standards, guidelines, and restrictions.
Both study teams note a number of limitations, including the potential for exposure to be misclassified, and they emphasise how additional unmeasured variables may have impacted their findings. Furthermore, those without health insurance, kids and teenagers, and foreign nationals may not be covered by the results. When combined, these fresh findings offer a useful guide for upcoming national air pollution regulations.
-Raja Aditya
