Monday, May 29, 2017

Air Pollution Kills?

According to the World Health Organization (WHO) air pollution causes one in nine premature deaths in the world, and it is often reported that in the United States air pollution causes 200,000 deaths each year. Though none of us has ever known anyone who has died from air pollution...quantifying the impacts of air pollution is very complicated and uncertain.

In the United States the estimate comes from a 2013 MIT research paper that used 2005 air pollution data. The MIT’s Laboratory for Aviation and the Environment tracked near ground level air pollution from sources such as industrial smokestacks, cars, buses, trains, and commercial and residential heating throughout the United States, and found by comparing areas of higher pollution areas with lower pollution that air pollution causes about 200,000 early deaths each year. Air pollution from cars, trains, buses, and trucks was found to be the biggest contributor, causing 53,000 premature deaths, followed closely by power generation, with 52,000 deaths.

Air pollution in the form of fine particles with diameters smaller than 2.5 microns, called PM 2.5, lodge in the lungs which can aggravate other conditions both immediately and long term –cutting months off of lives. This fine particulate matter can have immediate health impacts: itchy, watery eyes, increased respiratory symptoms such as irritation of the airways, coughing or difficulty breathing and aggravated asthma. Long term health effects can result from both short-term and long-term exposure to particulate pollution. Exposure to particles can cause premature death in people with pre-existing cardiac or respiratory disease. Researchers are still working to identify which types and sources of particles are most hazardous to human health. When the scientists estimated the total impact of particulate air pollution, they determined that all those months taken off the lives of people with pre-existing conditions added up to be about equivalent to about 200,000 deaths each year.

Fine particulate matter is made up of particles that are emitted directly, such as soot and dust, as well as secondary particles that are formed in the atmosphere from reactions of precursor pollutants such as oxides of nitrogen (NOx), sulfur oxides (SOx), volatile organic compounds (VOCs), and ammonia (NH3). Particle are either directly emitted or formed in the atmosphere. Directly-emitted particles come from a variety of sources such as cars, trucks, buses, industrial facilities, power plants, construction sites, tilled fields, unpaved roads, stone crushing, and burning of wood. Other particles are formed indirectly when gases produced by fossil fuel combustion react with sunlight and water vapor. Many combustion sources, such as motor vehicles, power plants, and refineries both emit particles directly and emit precursor pollutants that form secondary particulates. Ammonium nitrate and ammonium sulfate are the principal components of secondary particulates.

In the MIT study they found that the largest number of emissions-related premature deaths came from road vehicles, with 53,000 early deaths per year attributed to exhaust from the tailpipes of cars and trucks. The scientists postulated that vehicles tend to travel in populated areas, increasing large populations’ pollution exposure and the exhausts are emitted close to the ground. While power plants are generally located far from most populations and their emissions are deposited at a higher altitude. Pollution from electricity generation still accounted for 52,000 premature deaths annually. The largest impact was seen in the east-central United States and in the Midwest: Eastern power plants tend to use coal with higher sulfur content than Western plants which contributes to fine particulate creation. Though changes in power generation fuel (the low price of methane from fracking) and coal plant regulations has decreased the amount of particulate matter emitted from coal fired power plants.

Unsurprisingly, most premature deaths due to commercial and residential pollution sources, such as heating and cooking emissions, occurred in densely populated regions along the East and West coasts. Pollution from industrial activities was highest in the Midwest, roughly between Chicago and Detroit, as well as around Philadelphia, Atlanta and Los Angeles. Industrial emissions also peaked along the Gulf Coast region, possibly due to the proximity of the largest oil refineries in the United States.

Just as I keep an eye on my water quality I also spot check the local air quality. As Bangledesh, India, Pakistan and China continue to spew more and more pollutants and particulates from their expanding automobile ownership and increasing numbers of power plants and industrial manufacturing the world level of particulate pollution slowly climbs up. While the pollution is most concentrated in their own cities, air pollution moves beyond borders. As the developing world expands their air pollution, the United States (and most of the western developed world) continues to reduce ours. 

The U.S. Environmental Protection Agency, EPA, requires states to monitor air pollution to assess air quality and ensure that they meet minimum air quality standards. Still, not all of the nation is monitored. The US EPA has established both annual and 24-hour PM2.5 air quality standards (as well as standards for other pollutants). The annual standard is now 12 ug/m3 (an AQI of 39). The 24-hr standard was recently revised to a level of 35 ug/m3 (an AQI of 99) and will remain unchanged. States will have until 2020 to meet this PM2.5 health standard that was last lowered in 2012. If you want to take a look at real time particulate pollution levels you can see what the monitors nearest your home are reporting. Note that the levels are reported in AQI (0-50 AQI is good air quality and 51-99 is moderate air quality). Long Park in Haymarket Virginia was reporting an AQI level of 3 as I was finishing this article. Long Park is about 3 miles from my house down route 15.

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