Fine particle air pollution is a public health emergency hiding in plain sight
Posted by admin on 15th November 2018
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Ambient air pollution is the largest environmental health problem in the United States and in the world more generally. Fine particulate matter smaller than 2.5 millionths of a meter, known as PM2.5, was the fifth-leading cause of death in the world in 2015, factoring in approximately 4.1 million global deaths annually. In the United States, PM2.5 contributed to about 88,000 deaths in 2015 – more than diabetes, influenza, kidney disease or suicide.

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

Developed countries have made progress in reducing particulate air pollution in recent decades, but much remains to be done to further reduce this hazard. And the situation has gotten dramatically worse in many developing countries – most notably, China and India, which have industrialized faster and on vaster scales than ever seen before. According to the World Health Organization, more than 90 percent of the world’s children breathe air so polluted it threatens their health and development.

As environmental health specialists, we believe the problem of fine particulate air pollution deserves much more attention, including in the United States. New research is connecting PM2.5 exposure to an alarming array of health effects. At the same time, the Trump administration’s efforts to support the fossil fuel industry could increase these emissions when the goal should be further reducing them.

The average human hair is about 70 micrometers in diameter – 30 times larger than the largest fine particle.
EPA

Where there’s smoke …

Particulate matter is produced mainly by burning things. 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 suite of sources in developing countries, but often with more industrial production and more burning of solid fuels in homes.

Wildfires are also an important and growing source, and winds can transport wildfire emissions hundreds of miles from fire regions. In August 2018, environmental regulators in Michigan reported that fine particles from wildfires burning in California were impacting their state’s air quality.

Most deaths and many illnesses caused by particulate air pollution are cardiovascular – mainly heart attacks and strokes. Obviously, air pollution affects the lungs because it enters them as we breathe. But once PM enters the lungs, it causes an inflammatory response that sends signals throughout the body, much as a bacterial infection would. Additionally, the smallest particles and fragments of larger particles can leave the lungs and travel through the blood.

Emerging research continues to expand the boundaries of health impacts from PM2.5 exposure. To us, the most notable new concern is that it appears to affect brain development and has adverse cognitive impacts. The smallest particles can even travel directly from the nose into the brain via the olfactory nerve.

There is growing evidence that PM2.5, as well as even smaller particles called ultrafine particles, affect children’s central nervous systems. They also can accelerate the pace of cognitive decline in adults and increase the risk in susceptible adults of developing Alzheimer’s disease.

PM2.5 has received much of the research and policy attention in recent years, but other types of particles also raise concerns. Ultrafines are less studied than PM2.5 and are not yet considered in risk estimates or air pollution regulations. Coarse PM, which is larger and typically comes from physical processes like tire and brake wear, may also pose health risks.

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