Air Quality in Southern California - Time for a Paradigm Shift

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by Arthur Winer

As the result of an unprecedented and aggressive long-term air pollution control program for both mobile and stationary sources, the Southern California region can look back on thirty years of dramatically improved air quality and claim for itself one of the most remarkable environmental success stories anywhere in the world. Despite enormous growth – a doubling of population and a near tripling of vehicle miles traveled – the region now meets the federal air quality standards for four of the six pollutants originally regulated by the 1970 Clean Air Act, has eliminated all first, second and third stage air pollution alerts, and has reduced peak ozone levels by more than two-thirds.

These stunning achievements represent a triumph of government at every level, supported by an insistent public demand for clean air, and the sometimes reluctant but resourceful ability of business and industry to respond innovatively to stringent, technology-forcing measures adopted by the California Air Resources Board (ARB) and the South Coast Air Quality Management District (SCAQMD). The creation of the SCAQMD was itself a rare triumph of regional government in Southern California when in 1976 the counties of Los Angeles, Orange, Riverside and San Bernardino merged into this single regional air quality agency, implicitly recognizing that air pollution did not respect political boundaries.

However, despite thirty years of impressive progress including improved visibility, lowered concentrations of harmful gases and particles, and elimination of eye irritation there remains the potential that continued growth in population, emission sources, and vehicle miles traveled may endanger this record. Indeed, until the 2004 smog season, with its exceptionally clean meteorology and significantly lower pollution levels, the air quality records of the preceding five years suggested that improvements in levels of ozone and other pollutants were stalling (Figure 1), and that the region faces new challenges if we are to maintain our clean-air initiatives.

This essay discusses two main hypotheses concerning Southern California's air quality issues. First, although it is essential to continue to implement the most cost-effective clean-air technologies available, technology alone is unlikely to rescue us from the pressures of continued growth to the degree it has in the past. Instead, if long-term air quality solutions are to be found, they are likely to be more dependent on other critical regional issues, including transportation, land use planning, smart growth, energy conservation, fuel choices, and environmental justice. Second, while it is essential to continue our efforts to address the well-understood regional problem of photochemical smog, we need to confront a major new air quality concern on a completely different spatial scale, namely the highly localized health impacts of directly-emitted vehicle emissions. These health impacts which are not yet well recognized by regional policy-makers are a function of traffic densities and proximity to major roadways, and will further complicate land-use, transportation, smart growth and environmental justice policies in the region. We will show that the same set of regional planning issues is inextricably bound into both of these major air pollution problems, and that a new paradigm is required to address them effectively.

We begin by presenting a summary of the growing literature on the health impacts of direct exposure to vehicle exhaust, discuss what close proximity to roadways means, and describe implications for environmental justice concerns and for in-vehicle exposures. We then suggest a number of strategies for reducing exposures to vehicle emissions but also discuss the current limits of technological fixes, and the necessity for more effective transportation, land-use, and smart growth policies with respect to air quality issues. Finally, we suggest additional policy measures for improving regional air quality and note direct evidence of the benefits of further reducing exposure to vehicle emissions and to photochemical smog, and conclude with an appeal for greater cooperation between all of the relevant stakeholders.

July 14, 2008