Particle pollution more toxic than thought

Californian researchers have concluded that the tiny dust particles which cloud the air in built-up areas are even more lethal than previously suspected.

In the US state 14,000 to 24,000 premature deaths are linked with exposure to the ultrafine particulates known as PM2.5.

These come from a variety of sources but by far the biggest contributor in California is exhaust emissions from traffic.

Researchers from the California Air resources Board have reviewed existing studies on the health impact of particulates and interviewed experts in the field for this latest report.

While exposures to particulate matter have long been known as a serious health threat, new information suggests that the pollutant is even more toxic than previously thought.

“Particle pollution is a silent killer,” said ARB chairman Mary Nichols.

“We must work even harder to cut these life-shortening emissions by further addressing pollution sources head-on.”

While the new data reveals a greater threat from PM2.5, the state’s previous efforts to reduce emissions throughout the state have been successful.

The ARB in coordination with the 35 air districts throughout the state continues to develop and implement strategies of aggressive air pollution control.

These measures have been so effective for the last two decades that PM exposures have been reduced in California’s major populated areas.

Since the official year-round monitoring of ambient PM2.5 began in 1999, concentrations have decreased 30% across California, most notably in the South Coast and the San Joaquin Valley regions.

Additionally, in 2000 ARB adopted a risk reduction plan that targets all diesel PM sources in California. As part of the plan, cleaner diesel fuels and new diesel engines have been developed.

Other regulations have been adopted to address diesel engines already on the road, including those in waste collection vehicles, transit fleet, school buses, stationary engines, transport refrigeration units and portable engines.

Later this year, ARB will consider rules to significantly cut diesel particulate emissions from private truck fleets.

The draft report is available online for comment.

Sam Bond

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