Written and posted by BAAQMD, January 2011.

Air quality in the Bay Area has improved significantly in recent years due to tight regulation of emissions from all sources, including industrial facilities and motor vehicles. Smoggy days have declined substantially over the past 40 years. Despite this progress, the Bay Area continues to exceed state and/or national standards for ozone (smog) and particulate matter (PM) on a limited number of days each year.

How will climate change impact air quality in the Bay Area?

Although it is difficult to predict how climate change will impact the local climate, climate change may worsen air quality in the Bay Area. Since the Bay Area only experiences smoggy conditions on hot days, an increase in the number and/or intensity of hot days would increase levels of ozone in the region. Air quality modeling suggests that increased ozone levels due to climate change could potentially offset 10 years or more of pollution control efforts in the Bay Area between now and 2050.

Climate Change caused by world-wide emissions of GHGs could impact Bay Area ozone levels through any and all of the following:

• longer and more frequent heat waves;
• more frequent severe temperature spikes;
• increased length of the ozone season;
• increased VOC emissions from trees and other biogenic sources of VOCs due to higher temperatures;
• increased evaporative emissions of VOCs from storage tanks, solvents, and motor vehicles;
• increased atmospheric water vapor, higher humidity; and
• reduction in wind and vertical mixing that disperse pollutants

Many strategies that reduce greenhouse gas (GHG) emissions, such as increased energy efficiency and reductions in fuel use, also reduce air pollutants that harm public health. By looking for solutions that reduce both GHGs and air pollutants, we can address climate change and poor air quality more efficiently.

Air pollutants that contribute to health problems in the Bay Area

Ozone: Ground-level ozone is commonly known as “smog”. Ozone is not directly emitted into the air; instead, it is formed when ozone precursors, nitrogen oxides (NOx) and volatile organic compounds (VOCs), react in the atmosphere in the presence of sunlight. NOx and VOCs are emitted by motor vehicles, industrial facilities, and consumer products. Ozone exposure can cause chest pain, coughing, and respiratory diseases.

Particulate Matter (PM): PM consists of tiny particles or liquid droplets suspended in the air that can penetrate deep into our lungs. Health studies show that exposure to PM can cause serious health effects, including respiratory diseases, lung damage, and premature death. PM is emitted directly into the air, and also formed from reactions of gaseous pollutants. Sources of PM include diesel engines, gasoline engines, wood smoke, industrial facilities, and construction.

Toxic Air Contaminants (TACs): TACS are pollutants that can cause serious health effects even in low concentrations. Highly toxic TACs, like benzene and hexavalent chromium, can cause severe health problems including cancer, birth defects, and brain damage. Diesel particulate matter (PM emitted from diesel engines) is the most prevalent TAC in the Bay Area and the state.

The Bay Area 2010 Clean Air Plan

The Bay Area Air Quality Management District (Air District) is the agency charged with regulating stationary sources of air pollution and improving overall air quality to protect public health in the Bay Area. The Bay Area 2010 Clean Air Plan (CAP) presents an integrated plan to reduce emissions of air pollutants and GHGs in the region. The CAP lays out a comprehensive set of control measures to reduce pollutants from both stationary and mobile sources. Due to the correlation between high heat and ozone formation, the District has included measures to reduce GHGs emissions for the first time in its 2010 CAP.

The 55 pollution control measures included in the 2010 CAP fall into the following categories:

• 18 Stationary Source Measures;
• 10 Mobile Source Measures;
• 17 Transportation Control Measures;
• 6 Land Use and Local Impact Measures; and
• 4 Energy and Climate Measures.

The Air District will implement the CAP control measures by adopting and enforcing regulations to reduce emissions from stationary sources. In addition, the Air District will implement the CAP measures by means of grants and incentives, public outreach, guidance documents, and partnerships with regional agencies, local governments, the business community, community groups, and other stakeholders.

Over the next several years the Air District, with its other partners, will implement a number of innovative measures described in the CAP, such as an indirect source review regulation, an enhanced CEQA program, land use guidelines for local agencies, urban heat island mitigation, and assisting local governments in the development of Community Risk Reduction Plans and climate action plans.

Resources:

• The Bay Area 2010 Clean Air Plan
• How Bay Area residents can improve air quality
• Information on BAAQMD regulations
• BAAQMD Grant & Incentive Programs
• Health Effects of Ozone and Particle Pollution (American Lung Association)
• The US EPA’s webpage on health effects of climate change