An estimated 152 million Americans live in areas that do not meet national air-quality standards. In these locations, the ambient air contains enough pollutants to affect residents’ health. Exposure to persistent ground-level ozone (smog) and particle pollution has been tied to rising rates of heart disease, lung cancer and childhood asthma. Recently, both the World Health Organization and the American Academy of Pediatrics issued reports linking these pollutants to children’s decreased lung functioning and increased risk of respiratory infections.

In Maryland, 15 counties are not in attainment of Clean Air Act standards. Baltimore ranks 11th of the 25 most-ozone polluted cities in the American Lung Association’s 2005 National State of the Air Report.

Despite sustained corrective efforts by industry and regulators, poor air quality is a fact of life in this region. Traditional air-quality planning has focused on limiting pollution from emitting sources. Innovative strategies may help improve air quality.

Clean Air Act Standards
Under the Clean Air Act, national ambient air-quality standards have been set for certain common air pollutants. The U.S. Environmental Protection Agency (EPA) uses health-based criteria for setting permissible levels of ground-level ozone, particulate matter, carbon monoxide, nitrogen oxides, lead and sulfur dioxide. A geographic area is in attainment of the Clean Air Act’s primary standards when the level of each of these pollutants does not exceed the level determined to negatively impact human health.

The Clean Air Act allows states flexibility in planning how to meet and maintain national ambient air-quality standards. Each state or district, with the legal authority to manage its air program, prepares air-quality implementation plans (SIP) describing the measures that will be used to reduce pollutant levels and/or maintain national standards. These plans must be approved by the EPA. Once approved, SIPs are enforceable in court.

State Air-Quality Planning
In Maryland, controls placed on emitting sources, such as power plants, gas stations, body shops and cars, have reduced ozone-forming pollutants by approximately 40 percent from 1990 levels. However, this strategy has not reduced smog enough to meet Clean Air Act standards. Pollutants transported from Ohio and points south continue to degrade the air quality in much of the state.

New national ozone and particulate-matter standards will become effective in June 2005. These standards must be attained by 2010 or the state could face loss of federal funding.

The Maryland Department of the Environment is scheduled to begin drafting its Ozone SIP early next year. Maryland’s Ozone SIP must be submitted to the EPA by June 2007; the Particulate Matter SIP is due April 2008.

Emerging and Voluntary Measures
The EPA issued a new policy regarding incorporating emerging and voluntary measures into SIPs in September 2004. This policy is designed to foster innovative air-quality improvement strategies that have not typically been approved in SIPs. It allows SIPs to include 1) emerging measures that foresee pollution reductions that may not yet be fully quantifiable and 2) voluntary measures that are not enforceable against an individual source.

The policy sets a presumptive limit on states’ use of emerging and voluntary measures in SIPs. Emerging and voluntary measures can only account for 6 percent of the emission reductions necessary to meet Clean Air Act requirements. There are also practical challenges with demonstrating progress towards improvement for longer term strategies. Nevertheless, since many source controls have already been installed, scientists, policymakers and the public are currently proposing new strategies as emerging or voluntary measures in SIPs.

Innovative Strategies for Cleaner Air
The U.S. Forest Service is exploring the feasibility of using urban forests to improve air quality. Scientific research shows that increasing tree canopy cover can reduce peak ozone concentration levels. The Forest Service is analyzing the logistical issues associated with incorporating large-scale tree plantings into state air-quality improvement planning.

The environmental agencies in Georgia and Texas are considering strategies designed to address the Heat Island Effect (the rise in temperature due to an increased number of buildings and impermeable surface area). Because the emission of many pollutants and ozone-forming chemicals is temperature-dependent, reducing air temperature can improve air quality by reducing ozone formation. Studies indicate that shade trees, permeable pavement and reflective rather than heat-absorbing roofs work to offset air pollution in urban centers.

Increasing energy efficiency and maximizing energy conservation improves air quality by decreasing reliance on power plants. Energy-efficient construction and long-term commitments to alternative/zero-emission energies are being advanced as measures to decrease regional air pollution.

In many parts of the United States, traditional emission-control strategies have already been implemented to address the most acute air pollution problems. While control technologies have limited source emissions, air quality has not improved sufficiently to assure a healthy environment for almost half of the population. Established source-control measures need to be supplemented by more comprehensive strategies designed to create an environment that actively reduces pollution.