Research: Air Quality and Environment

Transportation behaviors and trends have a significant environmental impact.  Transportation contributes 27 percent of the nation’s greenhouse gas emissions, and this source saw a greater absolute increase during the period from 1990 to 2013 than any other sector (e.g. industry, commercial, electricity, etc.) (EPA, 2015). Exposure to air pollution has been connected to elevated risk of asthma, lower lung function, higher blood pressure, higher cardiac-related mortality, and lower overall life expectancy (National Institute for Transportation and Communities, 2014; Pope 2009). Air pollution exposure is also an environmental justice concern, with disparities in exposure by demographic and socioeconomic characteristics (Jones et al., 2014; Mejia et al., 2011).

Reducing air pollution exposure can be achieved by decreasing the concentration of pollutants and the length of exposure. By shifting shorter trips to walking and biking, Safe Routes to School programs can improve air quality by reducing vehicle trips and miles traveled. Reducing travel volumes is also important for minimizing children’s exposure to pollution during active transportation to school. School site location and design can also influence air pollution exposure, affecting exposure from major roadways and other sources on the way to school and during the school day (EPA, 2015).

The literature in this section explores the relationship between transportation mode choice and vehicle emissions, air pollution, and health impacts.

RESEARCH HIGHLIGHTS:

  • Motor vehicles are responsible for up to 30% of total greenhouse gas emissions (Solomon et al., 2009)
  • In one study, a 5% increase in neighborhood walkability (as measured using an index based on residential density, street connectivity, land use mix, and retail floor area ratio) was associated with:
    • 6.5% fewer vehicle miles traveled (VMT) per capita
    • 5.6% fewer grams of nitrogen dioxide per capita
    • 5.5% fewer grams of volatile organic compound (VOC) emitted per capita (Frank, et al., 2006)
  • Living in majority white neighborhoods has been associated with lower air pollution exposure, and living in majority Hispanic neighborhoods has been associated with higher pollution exposures (Jones et al., 2014)
  • Lower socioeconomic status has been connected with closer school proximity to pollution sources (Mejia et al., 2011)
  • Rates of asthma have been associated with closer residential distance to a freeway among children (Gauderman et al., 2005); exposure to roads with high vehicle traffic (representing near-road traffic-related pollution) accounted for 14% of all asthma cases across 10 European cities (Perez et al., 2013)
  • In a study model, substitution of cycling for short vehicle trips had the potential to reduce gasoline demand about 35% and CO2 emissions by 12% (Higgins et al., 2005)
  • Health benefits of shifting from car to bicycle was associated with greater benefits from increased physical activity (3-14 months of life gained) compared with potential effects of inhaled air pollution (0.8-40 days of life lost) (de Hartog et al., 2010)
  • Improved air quality accounted for as much as 15% of the overall increase in life expectancy in one study (Pope et al., 2009)
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A recent report on road-traffic-related air pollution by the UK National Institute for Health and Care Excellence (NICE) urges for urban speed reduction to improve air quality.

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Key takeaway:

  • The long-term health benefits of physical activity through active travel generally outweigh the health risks of air pollution.
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Key takeaway:

  • The long-term health benefits of physical activity through active travel generally outweigh the health risks of air pollution.
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Key takeaway:

  • This study found that in rural areas, schools are the most common settings for policy and environmental interventions for physical activity.
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KEY TAKEAWAY:

  • The long-term health benefits of physical activity through active travel generally outweigh the health risks of air pollution.
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Importance:  Health is inextricably linked to climate change. It is important for clinicians to understand this relationship in order to discuss associated health risks with their patients and to inform public policy.

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Key takeaway: Cycling measures can improve urban air quality levels as part of a multifaceted approach toward reducing road traffic.

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Key takeaway: Bicyclists’ exposure to air pollution can vary with roadway and travel characteristics, and transportation-related strategies can reduce exposure.

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CONTEXT:  Exposure to elevated concentrations of traffic-related air pollutants in the near-road environment is associated with numerous adverse human health effects, including childhood cancer, which has been increasing since 1975.

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Objectives. We described the associations of ambient air pollution exposure with race/ethnicity and racial residential segregation.

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