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California Environmental Health Tracking Program

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Last Edited: 9/28/2010

Air Contaminants: Traffic Pollutants

Traffic pollutants are a group of air contaminants that are generated by cars and trucks.  Traffic pollutants are harmful to human health.  To learn more, scroll down or select from a topic below.

What are traffic pollutants?

Cars and trucks produce pollutants that can be harmful to your health.  These include:

  • Diesel Particulate Matter (PM)
  • Nitrogen Oxides (NOx)
  • Carbon Monoxide (CO)
  • Volatile Organic Compounds (VOCs)

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What are the health effects of traffic pollutants?

  • Diesel particulate matter (PM)
  • Nitrogen oxides
    • Nitrogen oxides can cause increased sensitivity to allergens. 
    • When nitrogen oxides combine with VOCs in the presence of sunlight, they form ground-level ozone
      • This ozone can cause difficulty breathing, exacerbate asthma, and cause lung inflammation
      • Over time, untreated inflammation can result in permanent damage to the lungs
  • Carbon Monoxide
    • Carbon monoxide can cause chest pain in people with heart problems, headaches, nausea, decreased mental alertness, and death at very high levels
  • Volatile organic compounds (VOCs)
    • VOCs from vehicles include formaldehyde, acetaldehyde, acrolein, 1,3-butadiene, and benzene-- all of these chemicals can cause cancer

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Who is at risk?

People who live close to busy roads may be at higher risk for exposure to traffic pollutants. People who spend a lot of time inside vehicles are also at risk.


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Measures of traffic pollutants

There are many ways to measure traffic pollutant exposure. 

  • Some researchers measure distance to a major road
  • Others examine the total length of road within a certain area
  • Others measure one pollutant that may indicate exposure to all traffic pollutants

Below is the traffic pollutant measure currently available on our air quality data query:

  • Percent of population living near busy roads (2004 traffic data and 2000 census data)
    • This measure gives the percent of the population in each county living within 300 meters of a busy road
    • A busy road is defined as having more than 10,000 vehicles drive on it each day
    • Living near busy roads is associated with a variety of health outcomes, including heart disease, asthma, and reproductive outcomes
    • Distance from busy roads has been found to be a proxy for exposure to traffic-related pollutants

What does this measure tell us?

  • This measure can be used to provide an indication of potential exposure to pollutants such as PM2.5, NOx, and VOCs
  • This measure can be used to estimate the proportion of the population at a greater risk for a variety of health outcomes, including heart disease, asthma, and reproductive outcomes

What can't this measure tell us?

  • This measure cannot tell us how much of any pollutant people living near busy roadways are exposed to
  • This measure cannot tell us about other important factors related to exposure, such as upwind/downwind location
  • This measure cannot tell us about a person’s total individual exposure, which depends on where they work, go to school, walk, drive, and play

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