The California Air Resources Board (CARB) has adopted a plan that demonstrates to the US Environmental Protection Agency how the San Joaquin Valley air basin will attain each of four federal standards for fine particulate matter by regulatory deadlines.

Meeting standards for fine particle pollution, or PM_2.5, is the San Joaquin Valley’s most critical air quality challenge. The San Joaquin Valley has the worst particulate matter pollution in California—and the worst in the nation for annual federal standards. The newly adopted 2018 Valley PM_2.5 Plan is expected to result in significant improvement in air quality by 2024.

The plan features air pollution controls on important mobile, stationary and area-wide sources that will achieve the needed reductions of PM_2.5 and nitrogen oxides (n)ox emissions to reach attainment. NO_x, produced in the air during combustion, is an important precursor for fine particle pollution.

Particulate matter, which can be made up of soot, soil, dust and sulfate particles, comes from a variety of sources, but primarily from the burning of carbon-based fuels, such as gasoline, diesel and wood. In the San Joaquin Valley, car and truck emissions make up about half of measured airborne PM_2.5, and local sources, such as wood smoke and dust, make up the other half.

Despite progress—existing CARB strategies such as engine and fuels standards have reduced Valley NO_x emissions by 60% and Valley Air District programs have reduced PM_2.5 emissions by nearly 40%—PM_2.5 emissions are expected to rise as the population grows.

Currently, the Valley is designated non-attainment for the following federal health-based standards for PM_2.5: the 1997 24-hour (65 micrograms per cubic meter) and annual (15 ug/m³) standards, and the 2006 24-hour (35 ug/m³) and 2012 annual (12 ug/m³) standards. Deadlines for attaining these standards are 2020, 2024 and 2025, respectively. (The 2020 deadline is for both 1997 standards.)

The plan relies on both regulations and financial incentives to accelerate emissions reductions. Securing approximately $5 billion in incentive funding by 2024 will be critical for implementing the plan. CARB said it is committed to working with the air district and stakeholders to help secure a steady stream of needed funding.

Measures for reducing emissions include:

• New regulations targeting emissions from heavy-duty trucks, including an inspection and maintenance program, a low-NO_x engine standard and a low-emission diesel fuel requirement.

• Tightened controls on residential wood-burning stoves and fireplaces, and enhanced incentives for cleaner-burning alternatives.

• Enhanced incentives for purchase of cleaner agricultural equipment and commercial underfired charbroilers.

• A suite of measures to reduce emissions of NO_x from flares, including flares at refineries, oil fields and landfills, internal combustion engines and boilers, among other sources.

CARB expects significant benefits from the plan. For example, the city of Fresno is predicted to see a 40% improvement in air quality between 2013 (the base year of the plan) and 2024, when the Valley is expected to attain the 35 ug/m³ standard). The Valley Air District has committed to an aggregate reduction of 1.3 tons per day of directly emitted PM_2.5 emissions and 1.9 tons per day of NNO_xOx emissions in 2024.