05 Dec 2018

California Air Resources Board Diesel Regulations

Who is the California Air Resources Board (CARB)?


The California Air Resources Board (CARB) oversees programs to reduce air pollution and fight against climate change. The CARB is a state agency primarily responsible for the 35 local control districts, and spearheads California’s efforts against global climate change.


Background of California Air Resources Board’s Diesel Program


In September 2000, CARB approved the Diesel Risk Reduction Plan designed to reduce diesel emissions from diesel-fueled engines. The goal is to reduce emissions and health risks by 85% by 2020.


The outline contained steps to:


  • Establish stringent emission standards, especially for new vehicles and engines
  • Reduce the sulfur content of diesel fuel for the use of Diesel Particulate Matter (DPM) emission control systems
  • Establish retrofit requirements for existing vehicles and engines
  • Evaluate alternatives to diesel-fueled vehicles and engines


Results for untreated diesel exhaust


In 1998, CARB classified DPM as a toxic air contaminant. Then in 2012, the International Agency for Research on Cancer named diesel engine exhaust “carcinogenic to humans”.

Most DPM is small, so it is easily inhaled. Most of the particles are exhaled. But some deposit in the deep portions of the lungs that are very susceptible to damage.

About 70% of the known cancer risks from air toxins in California are attributed to DPM.

DPM contributes to other health problems, too like:


  • Exacerbated chronic lung and heart diseases
  • Asthma
  • Childhood decreased lung function
  • New allergies
  • Premature death


Those most vulnerable of our population are the elderly with chronic health issues and the children as their lungs develop.

Even More Than Health


Diesel exhaust contributes to the visibility loss due to the haze across landscapes.  This is a scattering of sunlight and absorption by gases and particles from the emissions.

DPM also contributes to climate change. Large proportions of DPM is Black Carbon (BC). These BC emmissions are the 2nd greatest contribution to global warming. Carbon dioxide is the first. Black Carbon particles absorb sunlight, so warming occurs. That heat is spread to the air surrounding the warmed BC. Research has shown this is significant in the disappearance of Sierra Nevada snow. Melting of snow packs earlier in spring is a contributing factor to the decline in our water supply.


Trends in Levels of Diesel Exhaust Pollution


The CARB regulations are working. Over the last 3 decades, DPM levels dropped 68%. Levels continue to decline with more controls, and new technology options.

Over this same period of time the CARB regulatory programs led to reductions in statewide cancer risks even considering:

  • More vehicle miles traveled by diesel vehicles
  • Increased population
  • Higher gross state product (the growth in the economy)


The California Air Resources Board (CARB) institutes programs that reduce air pollution and fight global climate change. These programs work for the future of all Californians.