By Gurkiran Dhuga and Glen Pyle

Throughout the last few decades health concerns related to air pollution have been rising. Despite this focus there has been little research on the impact of air pollution on specific health conditions and mortality, even though there is a strong association between air pollution and overall life expectancy. A global study lead by researchers in Germany outlines the detrimental changes air pollution can have on human life expectancy. One surprising finding of the study was that cardiovascular disease, and not respiratory conditions, are the primary cause of early death from air pollution.

How Bad is Air Pollution?

The study by Lelieveld and colleagues drew from a dataset of 41 studies across 16 countries to determine the impact of air pollution on death from non-communicable diseases (NCD). The study utilized 6 categories of NCDs: lower respiratory tract infections, chronic obstructive pulmonary disorder, lung cancer, ischemic heart disease, cerebrovascular disease, and other NCDs. Exposure to compounds in air pollution, specifically fine particulate matter less than 2.5μm (PM2.5) and ozone (O3), was measured. From these data, the researchers calculated mortality rates, years of life lost (YLL), and loss of life expectancy (LLE) due to air pollution. YLL is an estimate of how many years prematurely a person died. LLE is a calculation of the decreased life expectancy of the entire population. These measures were calculated at global, regional, and national levels.

The study determined that worldwide 8.8 million people die from causes attributable to air pollution every year. The highest LLE – almost 4 years – was seen in East Asia, which may be due to the wide exposure to poor air quality. Australia had the lowest LLE at 0.2 years, likely due to their high air quality standards.

The differences in LLE for various risk factors, such as violence and tobacco smoking were examined for comparative purposes. Globally, the LLE for air pollution was 2.9 years which was higher than that for tobacco smoking which was 2.2 years, and for violence at 0.3 years.

Credit: Author provided

Air Pollution and Cardiovascular Health

Not only does air pollution result in premature death, but it is also associated with a plethora of chronic health conditions. Air pollution negatively impacts sleep, fertility, and pregnancy. Air pollution also impacts the cardiovascular system, although this is often overlooked. Somewhat surprisingly, the study by Lelieveld and colleagues found that most of the premature deaths from air pollution were due to ischemic heart disease and cerebrovascular disease.

Both short-term and long-term exposure to air pollution can have adverse effects on cardiovascular health. Short-term exposure to particulate matter increases the risk of developing cardiac arrhythmias, also known as irregular beating of the heart. Cardiac arrhythmias increase the risk of a heart attack, which partly explains why exposure to air pollution is associated with a higher risk of a heart attack. Long term exposure to air pollution, notably traffic-related pollutants, has also been linked to an elevated risk of hypertension. Furthermore, associations have been made between air pollution and heart failure, coronary artery disease, and cerebrovascular disease. Generally speaking, air pollution has been correlated with many damaging effects on the cardiovascular system. The study by Lelieveld quantifies this impact and shows that the negative impacts on the cardiovascular system are among the most significant health issues linked to air pollution.

Not All Air Pollution is Created Equal

Although air pollution generally has detrimental impacts on health, different sources of air pollution have different levels of toxicity. In decreasing order, the most toxic particles come from diesel exhaust, gasoline exhaust, biomass burning, coal combustion, and road dust. Given these toxicity profiles, it is likely that traffic is the largest contributor to the toxicity of PM2.5. Since PM2.5 can be composed of distinct particles which have unique toxicities, different particle types may explain the variable effects on human health.

It is also likely that smaller particles have more damaging effects on the body as they can penetrate deeper into the lungs and enter the blood circulation. For instance, the small particles in diesel exhaust cause cardiovascular dysfunction. The damage to the cardiovascular system can come from the particles that circulate in the blood where they can directly damage blood vessel walls, vascular muscle, or even the muscle of the heart.

Lowering the Risk By Raising the Bar

Worldwide, the LLE for all air pollution could be lowered to 1.8 years by removing fossil fuel-related air pollution, and to 1.2 years by removing all pollution created from human activity.

The question remains, how do we reduce air pollution to prevent these dangerous health conditions and what impact would these changes have on life expectancy? Given the high toxicity of diesel and gasoline exhaust particles, it has been highly recommended to switch to low-emission fuels and vehicles, as well as cleaner heavy-duty diesel vehicles. There have also been recommendations for citizens to utilize public transport or carpool to reduce the use of fossil fuels.

Moreover, to decrease biomass burning, which occurs with the burning of agricultural land, it is necessary to change clearing methods. Biomass burning is a common practice in southeast Asia where it is a significant contributor to the poor air quality that characterizes the region. In Chiang Mai, Thailand, measures implemented to lower biomass burning led to a reduction in mortality between 2009 and 2016.

Overall, there are a plethora of interventions to lessen air pollution. However, it is essential that multiple interventions be used to effectively decrease air pollution and improve health.

One unintentional intervention that was recently implemented was the decline in human activity due to the current COVID19 pandemic. This decline in air pollution due to reduced human activities such as commuting has resulted in major cities across the world having large reductions in PM2.5. By permanently removing air pollution caused by these human activities, 25 to 80% of LLE can be avoided. Thus, we are capable of reducing air pollution, and the impact of these actions will improve global health.

Next Steps

To further our understanding of air pollution and the human body more research must be conducted. Along with supporting future research on air pollution we must act to decrease air pollution worldwide. These actions should be accompanied with alternate options for travel, manufacturing, and agriculture to avoid economic losses that could also negatively impact human health, albeit in a different way.

Gurkiran Dhuga is a student of Biomedical Sciences at the University of Guelph and an Undergraduate Research Assistant.

Glen Pyle, PhD, is a Professor of Molecular Cardiology at the University of Guelph, and an Associate Member of the IMPART Team Canada Investigator Network at Dalhousie Medicine.