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Los Angeles cleans up despite rising car numbers

Despite rising numbers of cars on the road, the levels of dangerous air pollutants are show rapid decline, new data from Los Angeles shows.

The US’ second biggest city shows that levels of some vehicle-related air pollutants  in the city have decreased by about 98 per cent since the 1960s; even though residents there are now using three times as much gasoline and diesel fuel, driven by rising car numbers.

NOAA graph showing how gasoline use has risen, although VOC air pollutant levels have droppedBetween 2002 and 2010 alone, the concentration of air pollutants called volatile organic compounds (VOCs) dropped by half, according to a new study by US’ National Oceanic and Atmospheric Administration (NOAA) and published in the Journal of Geophysical Research.

The drop in air pollutants is being accredited to higher fuel efficiencies of modern cars, the requirement for cars to be fitted with catalytic converters and the use of reformulated fuels less prone to evaporate.

Ozone still a problem

But sadly, a drop in vehicle pollutants doesn’t mean there has been much of a decline over the last 50 years does not mean that ozone levels have dropped that steeply; the air chemistry that leads from VOCs to ozone is more complex than that. Ozone pollution in the Los Angeles Basin has decreased since the 1960s, but disappointingly, levels still don’t meet ozone standards set by the Environmental Protection Agency.

Traffic in Los Angeles

The steep decline is VOCs is nonetheless good news for the city; high levels can harm people’s respiratory systems and damage crops and other plants.

The level of decline surprised NOAA’s scientists though, even though the study’s researchers expected to see some kind of decrease resulting from California’s efforts to control air pollution. 

The magnitude of the drop in VOC levels was surprising, even to researchers who expected some kind of decrease resulting from California’s longtime efforts to control vehicle pollution.

“Even on the most polluted day during a research mission in 2010, we measured half the VOCs we had seen just eight years earlier,” NOAA-funded scientist, Carsten Warneke, Ph.D said. “The difference was amazing.”

The improvement in this one measure of air quality in Los Angeles may not surprise many longtime residents, Warneke said. People who lived in the city in the 1960s often couldn’t see nearby mountains through the smog; today, they often can.

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Faye Sunderland

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