Deadly Diesel Emissions Plummeting in California

"An Air Resources Board study, published (Sept. 21) in the prestigious scientific journal Environmental Science & Technology, shows that the cancer risk from exposure to the state’s most significant air toxics declined 76 percent over a 23-year period in California, a direct result of regulations targeting unhealthful emissions from these air pollutants," writes Melanie Turner for the ARB.

Diesel particulate matter, which is emitted mainly from trucks and buses and is responsible for most of the airborne cancer risk in California, declined 68 percent, as a result of the State’s regulatory efforts to clean up diesel exhaust.

The decline in toxic emissions is particularly significant in light of the state's steady population growth since 1990 (30 million) to 2012 (38 million), an increase of 27 percent, as well as an 81 percent increase in diesel vehicle-miles-traveled.

While the press release doesnt' indicate the increase in the number of diesel-powered vehicles, it credits "(t)the implementation of ARB’s recent diesel engine retrofit and replacement requirements (for) accelerated fleet turnover to cleaner trucks, and significant additional reductions are projected statewide."

“There is no way these improvements in public health would have occurred without a strong, well designed program to reduce public exposure to toxic air pollution,” said Air Resources Board Chair Mary D. Nichols.

The state's more recent significant diesel regulations began with a landmark regulation, the Statewide Truck and Bus rule adopted in December 2008 (posted here) under much controversy. Implementation began in 2011, requiring "truck owners to install diesel exhaust filters on their rigs, with nearly all vehicles upgraded by 2014," according to the 2008 press release.

The state's ultra-low-sulfur diesel fuel requirement became effective in 2006, four years ahead of the federal regulation.

While emissions from diesel-powered cars constitute a very small percentage of total diesel emissions, the ARB played a significant role in detecting the Volkswagen fraud, as the Silicon Valley Business Journal and ARB press release note.

Hat tip: Susan Frank, CA Diesel Truck & Bus Rule List.