Short- and long-term exposure to fine particulate matter (PM2.5) air pollution increases the risk of hospitalization for serious heart and lung disorders, according to two large US studies published in BMJ.
Overall, the results suggest that no safe limits exist for heart and lung health.
According to the Global Burden of Disease study, exposure to PM2.5 accounts for an estimated 7.6 percent of total global mortality and 4.2 percent of global disability-adjusted life years (a measure of years lived in good health).
In light of this extensive evidence, the World Health Organization (WHO) updated air quality guidelines in 2021, recommending that annual average PM2.5 levels should not exceed 5 mg/m3 and 24-hour average PM2. The level of .5 should not exceed 15. mg/m3 over 3-4 days each year.
In the first study, researchers linked average daily PM2.5 levels to residential ZIP codes for nearly 60 million U.S. adults ages 65 and older (84 percent white, 55 percent women) from 2000 to 2016. They then used Medicare insurance data to track hospital admissions over an average of eight years.
After taking into account many economic, health and social factors, average PM2.5 exposure over three years was associated with an increased risk of first hospitalization for seven major types of cardiovascular disease – ischemic heart disease, cerebrovascular disease, cardiovascular failure, cardiomyopathy, arrhythmias, valvular heart disease, and thoracic and abdominal aortic aneurysms.
Exposures between 9 and 10 mg/m3, which included the US national average of 9.7 mg/m3 during the study period, compared to exposures of 5 mg/m3 or less (WHO air quality guidelines for annual PM2.5), were associated with a 29 percent increased risk of hospitalization for heart disease.
On an absolute scale, the risk of hospitalization for cardiovascular disease increased from 2.59 percent at exposures of 5 mg/m3 or less to 3.35% at exposures between 9 and 10 mg/m3. “This means that if we managed to reduce annual PM2.5 to less than 5 ug/m3, we could avoid 23 percent of hospitalizations for cardiovascular disease,” the researchers say.
These cardiovascular effects persisted for at least three years after exposure to PM2.5, and susceptibility varied according to age, education, access to health services, and level of area deprivation.
The researchers say their findings suggest that no safe limit exists for the long-term impact of PM2.5 on overall cardiovascular health and that substantial benefits can be achieved through adherence to WHO air quality guidelines.
“On February 7, 2024, the US Environmental Protection Agency (EPA) updated the national air quality standard for annual PM2.5 levels, setting a stricter limit of no more than 9 ug/m3. This is the first since 2012 There is an update. However, this is still significantly higher than the 5 ug/m3 set by WHO. The newly published national standard was not sufficient to protect public health,” he added.*
In the second study, researchers used county-level daily data to track hospital admissions and emergency department visits for natural causes, cardiovascular disease and respiratory disease for 50 million US adults aged 18 and older from 2010 to 2016. Used data on PM 2.5 concentrations and medical claims. ,
During the study period, more than 10 million hospital admissions and 24 million emergency department visits were recorded.
They found that short-term exposure to PM2.5, even at concentrations below the new WHO air quality guideline limits, was statistically associated with higher rates of hospital admissions for natural causes, cardiovascular disease and respiratory disease, as well as emergency department visits. was significantly associated. For respiratory disease.
For example, on days when daily PM2.5 levels were below the new WHO air quality guideline limit of 15 mg/m3, a 10 mg/m3 increase in PM2.5 resulted in 1.87 additional deaths per million adults aged 18 years and older. Was associated with hospital admission. More than per day.
The researchers say their findings make an important contribution to the debate about the revision of air quality limits, guidelines and standards.
Both research teams acknowledge several limitations such as possible misclassification of risk and point out that other unmeasured factors may have influenced their results. Additionally, these findings may not apply to individuals without medical insurance, children and adolescents, and people living outside the US.
However, overall, these new results provide a valuable reference for future national air pollution standards.
