Air Quality (outdoor)

Port of Los Angeles, Los Angeles, CA.
Photo Credit: Used by permission of photographer: Colleen Beach (website:

Air pollutants such as carbon monoxide, ozone, particulate matter, and sulfur dioxide contribute greatly to poor air quality and have been found to cause significant health impacts, including lung cancer, cardiovascular disease, asthma and other respiratory problems linked to poor quality of life and premature mortality.

Unsurprisingly, air pollution and its attendant health risks are not evenly distributed across the population.  Children, the elderly, those living in proximity to high traffic volumes, and minority populations are all disproportionately affected.  A study measuring the number of toxic air compounds at different locations along the Los Angeles Basin found that residents living along highways with heavy traffic, particularly those in Huntington Park, Pico Rivera, Los Angeles, and Burbank (the core areas surrounding Downtown Los Angeles) were exposed to greater levels of toxic particulates and subsequently were at increased risk for cancer than those living elsewhere along the basin (South Coast AQMD, MATESII, 2000).  The Surface Transportation Policy Project has estimated that transportation-related public health costs from air pollution in the Los Angeles/Riverside/San Bernardino area alone total more than $2 billion per year (Ernst M, Corless J, and Greene-Roesel R, 2003).

California has been a national and world leader in reducing air pollution from both mobile and fixed sources.  While the State has improved air quality by 27% over the last several decades as the population has nearly doubled, there are still a significant number of people in various regions living with poor air quality making this a severe threat to public health.

Modifications such as smoke-free legislation, converting from “dirtier” fuels (e.g. coal or diesel) to less polluting fuels (e.g. natural gas), improved vehicle fuel efficiency, improved mass transit systems to decrease automobile use, and making cargo logistics systems more efficient could all significantly reduce air pollution. For instance, some transit systems in the U.S. are estimated to reduce annual emissions of volatile organic compounds by more than 70,000 tons, nitrogen oxides by 27,000 tons, and carbon monoxide by 745,000 tons (American Public Transportation Association ).

Efforts to understand the air pollution related health effects of proposed policies and projects need to differentiate between emissions and exposure and they need to examine differences in the distribution of pollutants as well as differences in susceptibility.  For instance, a policy that is expected to decrease ambient pollution levels over a region might lead to increased exposure to certain groups living close to a new facility.

Logic Framework

Diagram for Air Quality Pathway.

External Links


Air pollution can be assessed in three different ways:

  • Emissions: measuring the amount of gas and particulate matter emitted into the air by various   sources
  • Exposure: measuring levels of contact with harmful gases and particulates (usually respiratory in nature)
  • Ambient Levels: quantifying the amount of gas and/or particulate matter present in ambient air.  Ambient level is often used interchangeably with air pollution and can be measured in a number of ways, four in particular include: passive sampling, active sampling, automatic monitoring and spectroscopic techniques.  Passive sampling provides reliable information on ambient air quality using cost effective measures.  This method offers averages of pollution concentrations over an extended period of time (anywhere from weeks to months).  Active sampling enables measurements to be taken in short time intervals (on a daily basis).  Physical or chemical means are used in order to sample the air, but the analysis is performed in the lab.  Automatic monitoring techniques have the ability to “produce high-resolution measurements of hourly pollutant concentrations or better, at a single point.”   Samples can be analyzed and downloaded in real-time.  Finally spectroscopic techniques also allow for real-time measurements on a host of air pollutants.

Downstream Health Effects

Technological advances have significantly reduced the health effects of some air pollutants including carbon monoxide and sulfur dioxide; however ozone and particulate matter still remain considerably hazardous to population health.  It has been well documented, that ozone has the ability to aggravate airway passages.  Consequently, as ozone levels increase so do the rates of respiratory complications, emergency room visits, hospitalizations, diminished lung capacity, work and school absenteeism, and medication use.  Everyone is susceptible to these harmful effects; however asthmatics, children and the elderly are especially at risk.

Policies and Other Determinants

Key public policies can significantly affect air quality.  In general, air pollution is decreased by strategies that decrease commute times and promote alternative modes of transportation other than automobiles and trucks.  Some areas where public policy may be especially effective in reducing air pollution include:

  • Mass transit can improved service coverage, ease-of-use, that provides an attractive, time-efficient alternative to automobile use, for all community members, especially those with limited mobility options (e.g. the young and the elderly) (STPP, 2003; Centre for Sustainable Transportation, 2004; Environmental and Energy Study Institute, 2006).  Besides the “hard” measures of transit service, “soft” measures such as comfort and perceived security in the transit system are essential for increasing use, providing stress-free travel and creating opportunities for positive social interaction (Evan, Wener and Phillips, 2002; Evans and Wener, 2003)
  • Sprawl “is associated with high levels of driving, driving contributes to air pollution, and air pollution causes morbidity and mortality” (Urban Sprawl and Public Health). Cities that are heavily dependent on automobiles frequently reach hazardous air quality levels.  Sprawl increases travel time and forces people to travel out of their neighborhood for many everyday tasks, such as shopping, eating, working and going to school.  To be effective, efforts to control sprawl need to be combined with efforts to promote mixed use development and additional mass transit options
  • Travel time to/from work, school, shopping and recreational opportunities can contribute to hazardous levels of air pollution.  Travel time can be lessened through policies to reduce sprawl, promote mixed use development, support transit-oriented development, and improve the effectiveness of transportation systems