Air pollution is once more in the news. The Chinese announced that they will begin publishing the small particle, PM2.5 air pollution data for Beijing after January 23rd. Beijing, has been reporting their air quality based on PM10, which are particles smaller than 10 micrometers but larger than 2.5 micrometers in diameter. It has not reported particulate pollution of 2.5 micrometers or less. Combustion engines and coal burning power plants are key contributors to PM2.5 particles, and according to the US EPA and World Health Organization, the smaller, finer pollutants measured by PM2.5 are especially dangerous for human health. Studies have shown that people increased risk of asthma, lung cancer, cardiovascular problems, birth defects and premature death from particles smaller than 2.5 microns in diameter that lodge deep in the lungs.
Despite the official Chinese government report of 286 “blue sky” days last year, the air pollution in Beijing, home to over 20 million people, is easily seen by the smog that wraps the city’s apartment complexes and office buildings many days and by non-government sanctioned reports. The US Embassy in Beijing has their own PM2.5 monitoring station atop their building and has been reporting via an open Embassy Twitter Feed hourly PM2.5 pollution data to the chagrin of the Chinese government because it conflicted with official government data. The U.S. Embassy reported a series of readings beyond the scale of the air quality index, AQI, (which goes to 500) in fall of 2010 and levels over 300 this past fall which sparked a public campaign (over the internet) for better government reporting. Current air quality levels from the US Embassy are 325 which is “hazardous” according to the EPA.
In the United States, the Air Pollution Control District for Bakersfield, California, the city ranked by the American Lung Association as having the worst particulate matter (PM2.5) air pollution in the United States for the last several years, announced they had the worst air quality December recorded in over a decade. The area has already had four times as many unhealthy days this season than in the entire 2010-2011 winter season. In Bakersfield and the rest of the San Joaquin Valley PM2.5 concentrations are highest when cool stable weather and low wind speeds coupled with the Valley’s topography limit dispersion of pollutants and allow multi-day buildups of PM2.5 concentrations to occur along with the “Tule” fog which forms during this time of year. A lingering high-pressure system and dry La Nina conditions in the Pacific have created stagnant air in the valley. As a result car exhaust, agricultural emission and smoke from factories and chimneys has remained in place and this morning’s reading on the San Joaquin Valley Air Pollution Control District was 25 ug/m3 at Bakersfield with an AQI of 74 which is “moderate” air quality.
According to the Lung Association, the two biggest air pollution threats in the United States are ozone and particle pollution. Other pollutants include carbon monoxide, lead, nitrogen dioxide, sulfur dioxide and a variety of toxic substances including mercury that appear in smaller quantities. The United States Environmental Protection Agency, U.S. EPA, requires states to monitor air pollution to assess the healthfulness of air quality and ensure that they meet minimum air quality standards. 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 15 ug/m3 (an AQI of 49). The 24-hr standard was recently revised to a level of 35 ug/m3 (an AQI of 99). The recently challenged, Cross-State Air Pollution Rule (CSAPR) was intended in part to prevent pollution from one state from moving into other states and preventing them from meeting their goals, but the problems in the San Joaquin Valley are caused by local industry, the weather and the Sierra Nevada mountains to the east and the Coastal Range mountains to the west that wall the valley. The World Health Organization guidelines for PM2.5 are based on a mean level rather than the average that the U.S. EPA uses.
PM2.5 particles can be either directly emitted or formed via atmospheric reactions. Primary particles are emitted from cars, trucks, and heavy equipment, as well as residential wood combustion, forest fires, and agricultural waste burning. The main components of secondary particulate matter are formed when pollutants like NOx and SO2 react in the atmosphere to form particles. In the San Joaquin Valley the primary source of secondary particles are ammonium nitrate and ammonium sulfate which forms when nitrogen oxide and sulfur dioxide emissions from cars, trucks, and industrial facilities react with ammonia from agricultural operations.
Bakersfield, at the southern end of the San Joaquin Valley with a population of about 350,000 has some of the worst air in the United States. The city’s economy relies on agriculture, petroleum extraction and refining, and manufacturing. Cutting through the valley are the state's two main north-south highway corridors, the routes for nearly all long-distance tractor trailer rigs, the No. 2 source of particulate pollution in the valley. Also in the mix are millions of acres of plowed farmland and 1.6 million dairy cows and ammonia-laden manure they create. Without wind and rain, when the Tule fog forms, the air sits, trapped as if in a pot with a lid. With an air quality index a fraction of the level in Beijing local groups in Bakersfield have condemned the failure of the Air Quality Control Board to meet the federal standard by banning wood burning as the easiest source of particulate pollution that is easy to ban, but even with the ban in place for most of December, air quality remained at unhealthy levels with AQI over 100, but air quality has improved over the weekend.
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