SUSTRAN #19: Small Particulate Pollution



Evidence has mounted in recent years over the health impacts of particulate air pollution, particularly the smallest particles (less than 10 microns in diameter, PM10, and also those less than 2.5 microns, PM2.5) which can be inhaled deeply into the lungs, which remain in the atmosphere for the longest periods (up to a month), and which penetrate everywhere, including inside air-conditioned buildings and vehicles.

Last year, a Harvard University team released a study of the health impacts of air pollution on more than half a million adults in 151 US cities from 1982 to 1989. The study corrected for the effects of confounding variables such as smoking, obesity, and others. They found significantly elevated rates of premature death from cardiopulmonary disease and lung cancer in the cities with the highest levels of particulate air pollution. A recent report from the Natural Resources Defense Council in the US estimates that particulate air pollution shortened lives in the most polluted American cities by an average of one to two years. A November 1995 report from the British Department of Health's Committee on the Medical Effects of Air Pollutants (COMEAP), has called for much stricter standards for PM10. It says that the death rate rises by 1% per day when there is an increase in PM10 concentrations of 10 micrograms per cubic metre. The report further suggests that there seems to be no safe level for PM10. People with existing respiratory and cardiac disorders are most vulnerable.

Concentrating on measuring and reducing PM10 levels would be an improvement over the existing situation but the United States Environmental Protection Agency is urging that standards also be set for levels of particles of less than 2.5 microns in diameter (PM2.5). Pollution by this range of particles is rarely even measured at the moment.

The issue is further casting a spotlight on diesel vehicles. Diesel engines have long been identified as a major source of particulate pollution and more than 90% of the particles emitted are of less than 2.5 microns. Cities in the developing world, including most in the Asia-Pacific region, typically have much higher rates of diesel use for transport than high-income cities. Diesel fuel accounts for about half of the transport fuel consumed in cities like Bangkok, Jakarta and Manila. Furthermore, high sulfur content fuels, common in the region, produce the most particulate pollution. Emissions from poorly maintained diesel engines, which are the norm in low income countries, can be 10 to 15 times those of well-maintained ones.

Gasoline vehicles are not off the hook by any means. Non-tailpipe emissions (such as road dust and brake pad wear) are a significant source of particles and gaseous emissions such as nitrogen oxides and hydrocarbons are precursors for tiny acidic aerosol particles ("white smoke"), which may be among the most dangerous.

So far, SUSTRAN has little information on PM10 and PM2.5 measurements in the Asia-Pacific region or even how many countries have moved to start measuring using the PM10 or PM2.5 methods. If anyone has more information we would be very grateful.

Nevertheless, it seems certain that small particulate levels are frighteningly high in many cities. Already in 1992, according to a Japanese study, many parts of metropolitan Kuala Lumpur exceeded or came close to exceeding both the yearly and daily guidelines for PM10 levels (estimated from total suspended particulate matter or SPM levels). These guidelines are much less strict than those now being proposed in Britain and the USA. The 1991 report, "Urban Air Pollution in Megacities of the World" by UNEP and WHO found that SPM pollution was "very serious" in every one of the ten developing Asian cities in the survey. "Very serious" was defined as WHO guidelines being exceeded by more than a factor of two. In Jakarta it has been estimated that particulate air pollution results in more than 4000 extra deaths per year, which is at least five times more than are killed by road crashes! This is even without taking account of the latest research on small particles.

In Bangkok, particulate pollution has now reportedly overtaken lead as Bangkok's number one air quality concern. Politicians including the new Governor have reacted but have given most of their attention to the very visible dust from the many building sites in the booming city. But these are mainly large particles which are much less dangerous than the small particles which come mostly from vehicles.

In response to concern over air pollution and suspicions of official figures, there is a growing movement for community air quality monitoring, in which community groups have begun to measure air quality themselves and publicise the findings. To our knowledge such initiatives have so far begun in Japan, Korea and Australia. The SUSTRAN secretariat would very much like to get in touch with any groups in the Asia Pacific region which are doing such community air pollution measurements as well as any groups which would like to get involved.

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