Fewer air pollution deaths? Thank a regulation.

Poor air quality poses a significant environmental health hazard to people around the globe, with numerous compounds contributing to air pollution, including particulate matter (PM), ozone, nitrogen dioxide and sulfur dioxide – pollutants that can cause cardiovascular and respiratory diseases, as well as cancer.

According to the World Health Organization, about 90 percent of people worldwide breathe air with high levels of pollutants. In 2016, outdoor air pollution in both rural and urban areas led to an estimated 4.2 million premature deaths, with people in low- and middle-income countries accounting for 91 percent of the 4.2 million people who die prematurely each year from breathing tainted air.

Lowering outdoor air pollution levels requires deep collaboration from local, national and regional policymakers to improve and regulate industrial polluters, and the energy and transportation sectors, which, collectively, are the worst offenders.

Study results showed a decrease of nearly 50 percent in the number of deaths related to air pollution over the past two decades since America’s most stringent air quality protections took effect.

However, the future of air quality is not entirely grim. Since 1990, air pollution has been steadily declining in the United States, with improvements the result of national standards and government regulations on emissions.

Controls, meanwhile, have been put in place on energy production and emissions, controls that have worked in combination with advances in more efficient emission-reduction technologies to clean the air we breathe.

A road to better public health

Just how effective are those regulatory changes and technological advances? A recent study led by researchers at the University of North Carolina-Chapel Hill has calculated how better air quality is leading to less air pollution-related deaths. The results, published in Atmospheric Chemistry and Physics, show that improvements in air quality over the past two decades have nearly cut the number of air pollution deaths in half.

Led by Jason West and Yuqiang Zhang, the UNC-Chapel Hill team used data from a 21-year computer simulation model (1990 to 2010) to identify concentrations of two major air pollutants over the past two decades: ozone and PM2.5, small particulate matter with a diameter of 2.5 micrometers or less.

More harmful to human health than any other single air pollutant, PM2.5 can penetrate deep into the lungs; it's capable of entering the bloodstream. Most particulate matter comes from fuel use by vehicles and industrial production, though its sources are varied. It’s also capable of travelling long distances in the air to reduce air quality far from where it was generated. In Ontario, it’s estimated that half of all PM2.5 in the province originated in the United States.

After calculating air pollutant concentrations over the 21-year period, Zhang mapped deaths across America using data from the Centers for Disease Control and Prevention to determine those caused by air pollution. They looked at death rates for lung cancer, stroke, ischemic heart disease and chronic obstructive pulmonary disease – each of which have been associated with PM2.5 – as well as for respiratory disease linked to ozone.

Study results showed a decrease of nearly 50 percent in the number of deaths related to air pollution over the past two decades since America’s most stringent air quality protections took effect, including sweeping changes to the Clean Air Act in 1990. All together, air pollution deaths dropped from 135,000 in 1990 to roughly 71,000 deaths in 2010. (Though to put this figure in context, 71,000 deaths each year represents one out of every 35 deaths in the United States annually, more than the number of all traffic-related deaths and those from gun violence combined.)

Canada, meanwhile, has experienced comparable increases in air quality over the past few decades, with concentrations of air pollutants decreasing dramatically since the 1970s.

A 2017 study from The Fraser Institute showed a decline of five major air pollutants during this time, with current air quality levels meeting both national and international standards. But despite improvements, the country still experiences an estimated 14,400 premature deaths annually from poor air quality.

Zhang's UNC-Chapel Hill study shows how persistent a threat poor air quality remains to human health. And that despite regulations drastically improving public health outcomes, there’s still work to be done, even in the countries with some of planet’s cleanest air supplies.

“We’ve invested a lot of resources as a society to clean up our air,” says Jason West, the study's co-author and a professor of environmental sciences and engineering at the UNC Gillings School of Global Public Health. “This study demonstrates that those changes have had a real impact with fewer people dying each year due to exposure to outdoor air pollution.”