Long-term Exposure to Air Pollution: Does it Affect Mortality?

With global air quality reaching dangerous levels in many parts of the world, scientists and air quality specialists have begun closely studying the link between local air quality and public health. In these recent findings, researchers have suggested there may be a correlation between long-term exposure to air pollution and mortality rates.

By looking at some case studies around the world, we can get a better idea of this relationship. Then we can see if we need to take caution around our exposure to airborne pollutants, such as Particulate Matter (PM2.5, PM10).

Case Study: Auckland, New Zealand

According to a 2004 study done in Auckland, New Zealand, researchers found ambient air pollution levels to affect annual mortality rates significantly. From 1996-1999, exposure to heightened air pollution levels caused an estimated 268 deaths. Tragically, this accounted for 3.9% of all annual deaths in the region— more than double the number of deaths caused by automobile accidents each year (~103).

Overall, the study concluded that long-term exposure to air pollution resulted in a serious health risk for everyone, not just vulnerable groups.

Case Study: Ontario, Canada

An Ontario health study from 2021 provides a more recent look at the effects of long-term exposure to air pollution. Based on a study of over 80,000 Ontario participants, long-term exposure to elevated PM2.5 and NO2 resulted in an increased risk for mortality.

The study went as far as to suggest that even participants residing in relatively low-exposure regions could benefit from improvements in air quality.

Case Study: Danish Study

In another study, researchers observed the effects of exposure to specific airborne pollutants, such as PM2.5, black carbon, and ​​NO2 on public health and mortality rates. The findings were observed in the context of a larger set of cohort studies on air pollution exposure and human health.

Overall, the results showed a definite association between higher levels of exposure to PM2.5, black carbon, and NO2 and increased mortality rates. Results revealed that a 10 μg/m³ increase was associated with an average 1% increase in mortality for each airborne pollutant.

The study also went as far as to conclude that the highest increases in air pollution were associated with low-income areas.

Illness Associated with Long-Term Exposure to Air Pollution

According to a scientific review in Environmental Health, current air pollution levels are linked to several respiratory illnesses and cardiovascular diseases and increased mortality rates.

The Ontario study showed a significant increase in risk for non-accidental, cardiovascular, and respiratory mortality as a result of long-term exposure to PM2.5 and NO2. In New Zealand, the researchers concluded that every 1 μg/m³ increase in NO2 correlated with a 1.3% increase in overall mortality and a 1.8% increase in circulatory and respiratory mortality.

How PM2.5 Concentrations Affect Mortality

Based on several studies done in geographical regions around the world, there is a strong association between exposure to Particulate Matter (PM2.5) and risk of cardiovascular disease or mortality. Although there were many factors to consider (i.e., differences in particle composition, infiltration of particles indoors, and population characteristics), the increased mortality risk was anywhere from 6% to 11% per 10 μg/m³ increase in PM2.5 concentration.

For many regions in the world, where the daily PM2.5 concentration is anywhere from 3 to 8 times the WHO’s acceptable standard, this can seriously affect on public health.

A 2020 research study came to the shocking conclusion that even regions with PM2.5 levels below the US safety standard were causing an increase in mortality among the elderly. With16 years of data from 68.5 million participants, the study found that a 10 μg/m³ decrease in PM2.5 correlated to a 6-7% decrease in mortality rate.

Since the US air quality standard is currently 12 μg/m³, which is 2 μg/m³ higher than the WHO’s recommended limit of 10 μg/m³, lowering it by 2 μg/m³ could significantly decrease the risk of mortality among the elderly in the U.S. In other words, lowering the air quality standard to 10 μg/m³ of PM2.5 would save an estimated 143,257 lives per decade.

Air Pollution & Mortality: Is there a link?

The evidence from various studies in different parts of the world shows a robust link between long-term exposure to air pollution and mortality rates. Cardiovascular and respiratory-related illnesses are one of the most common causes of mortality as a result of this long-term exposure.

Among the possible airborne pollutants, PM2.5 and NO2 showed to be most closely linked with increased mortality rates.

How to Limit Exposure to Air Pollution and PM2.5 Exposure?

To avoid the long-term effects of air pollution, it's crucial we all stay informed about the air quality in our areas.

Monitor the Particulate Matter levels around the world with our free, real-time PurpleAir Map or join PurpleAir's mission to make air quality data accessible to everyone by investing in an air quality monitor for your home. 

Together, we can be informed and make changes in our daily habits and the community to improve air quality.