Air pollution: the world fills the lungs with PM2.5 killer

Ambient air pollution is the biggest environmental health problem in the United States and the world in general. Fine particles less than 2.5 million meters, called PM2.5, was the fifth leading cause of death in the world in 2015, with around 4.1 million deaths a year worldwide. In the United States, it caused approximately 88,000 deaths in 2015, more than diabetes, influenza, kidney disease or suicide.

Current data suggests that PM2.5 alone causes more deaths and illnesses than all other environmental exposures combined. For this reason, one of us (Bruges) recently wrote a book to try to spread the word.

Developed countries have made progress in reducing particulate air pollution, but more needs to be done to further reduce this risk. And the situation has deteriorated in many developing countries, especially China and India, which have industrialized faster and on a larger scale than before.

According to the World Health Organization, more than 90% of children in the world breathe so polluted air that it threatens their health and development.

As environmental health experts, we believe that the problem of air pollution by fine particles deserves much more attention. Research establishes a link between P2.5 exposure and an alarming range of health effects. In the United States, the Trump administration's efforts to support the fossil fuel industry could increase these emissions, while the goal should be to further reduce them.

Where there is smoke …

Particles are mainly produced by burning objects. In the United States, the majority of PM2.5 emissions come from industrial activities, motor vehicles, cooking and fuel combustion, often including wood. There is a similar set of sources in developing countries, but often with more industrial production and increased burning of solid fuels in homes.

Wildfires are also a growing source and winds can carry wildfire emissions away from burned areas. In August, environmental regulators in Michigan reported that fine particles from wildfires burning in California had an impact on the air quality of their condition.

Most of the deaths and many illnesses caused by airborne air pollution are cardiovascular in nature – primarily heart attacks and strokes. Clearly, air pollution affects the lungs as it enters our breathing. But once the particles enter the lungs, they cause an inflammatory response that sends signals throughout the body, as would a bacterial infection.

Smaller particles and larger particles can leave the lungs and travel in the blood.

The most notable new concern is that it appears to affect brain development and have adverse cognitive effects. The smaller particles can even travel directly from the nose into the brain via the olfactory nerve.

It is becoming increasingly clear that PM2.5, as well as even smaller particles called ultrafine particles, affect the central nervous system of children. They can also accelerate cognitive decline in adults and increase the risk of developing Alzheimer's disease in susceptible adults.

Other types of particles also raise concerns. Ultrafine is less studied than PM2.5 and is not yet taken into account in risk estimates or air pollution regulations. Coarse particles, which are larger and usually come from physical processes such as wear and tear on tires and brakes, can also present risks.

Regulation push and pull

The progress made by developed countries in combating air pollution, particularly particulate matter, demonstrates that regulation is effective. Prior to the creation of the United States Environmental Protection Agency in 1970, the air quality in Los Angeles, New York, and other major US cities today resembled that of Beijing and Delhi.

Increasingly stringent air pollution regulations since then have protected public health and undoubtedly saved millions of lives.

But it was not easy. The first regulatory limits on PM2.5 were proposed in the 1990s, after two key studies showed that they had major health effects. But the industry's criticism was fierce and included accusations that the science behind the studies was wrong or fraudulent. In the end, federal regulations were adopted and follow-up studies and re-analysis confirmed the original conclusions.

The Trump administration is now working to reduce the role of science in shaping air pollution policy and reversing the regulatory decisions made by the Obama administration.

On October 11, EPA Administrator Andrew Wheeler dissolved a scientific advisory group on air pollution that specifically addressed particle regulation. Critics have called it an effort to limit the role of scientific evidence in setting national air quality standards in order to protect health with a sufficient safety margin.

This is not the time to move away from the regulation of air pollution resulting mainly from the burning of fossil fuels.

• Douglas Brugge is Professor of Public Health and Community Medicine at Tufts University
• Kevin James Lane is Assistant Professor in Environmental Health at Boston University

– The conversation