People who live, work, or attend schools near major freeways experience negative health effects to increased exposure to air pollution. Children living or attending schools near freeways are at increased risk of asthma, allergies, bronchitis, and impaired lung function growth. Schools and parks located near freeways are particularly hazardous for children as their lungs are fragile and still developing. Long-term consequences from repeated exposure to freeway pollution include compromised adult lung functioning, lung disease, heart disease, and cancer.
In the last decade, scientific research conducted in Southern California, Northern California, the Netherlands, the UK, and other parts of the United States has amassed significant evidence of the negative health consequences of exposure to mobile source pollution for people who live, work, or attend schools near major freeways. “Mobile source pollution” is comprised of chemicals such as nitrogen dioxide, nitrous oxide, soot, carbon monoxide, as well as “fine” and “ultrafine particles” that are more specific to freeway pollution. Exposure to pollution among children living or attending schools near freeways is known to increase risks of:
Bronchitis and other respiratory problems 
Impaired lung function growth 
Of particular concern for schools located near freeways is that children’s lungs are fragile and still developing. According to researchers from the Southern California Particle Center (SCPC) at UCLA and collaborating institutions, “fine particles in air pollution, given their small size, are able to pass through the cellular tissue in the lungs and enter the circulation system. Their presence in the lungs may also induce a series of events that ultimately affect the heart (p. 1).”  Indeed, current research shows that repeated exposure to freeway pollution can result in critical long-term consequences, including:
Compromised adult lung functioning 
Lung disease 
Heart disease 
 Excerpted from a letter to Culver City School Board April 28, 2008 by Laura Abrams, PhD and others.  McConnell et al. (2006).  Brauer et al. (2002).  Janssen et al. (2003); Pope et al. (1995).  Gauderman et al. (2000).  Southern California Particle Center (n. d.).  Gauderman et al. (2007).  Brunekreefet al. (1997).  Jerrett et al. (2005); Pope et al. (2004).  Jerrett et al. (2005); Raashou-Nielsen et al. (2001).
"Scientists discussed several studies that have measured and modeled the impacts of vegetative barriers on near-road air quality. For research on solid barrier impacts, which are assumed to have similar effects as dense vegetation, wind tunnel studies and a field tracer study revealed consistent reductions in ground-level concentrations behind barriers relative to a clearing with no barriers.[3,4] The presence of a barrier led to an increase in vertical mixing, resulting in lower behind-barrier concentrations at the ground level. In addition, field and wind tunnel studies investigated the potential for enhanced capture of PM by vegetation. Generally, these studies have shown decreases in concentrations of ultrafine [5,6] and coarse  mode PM, with limitedreductions measured for PM2.5 mass. . . Participants also agreed that planting vegetation as a mitigation strategy may be most useful along existing roadways. For new and widened roadways, retaining existing vegetation is an important consideration."
-Excerpt from April 2010 U.S. Environmental Protection Agency conference entitled "The Role of Vegetation in Mitigating Air Quality Impacts from Traffic Emissions." (Studies cited in the report follow.)
1. Baldauf, R.W.; Bailey, C. ; Cook, J.R.; Cahill, T.A.; Khlystov, A.; Zhang, K.M.; Cowherd, C.; Bowker. G.E. Can Roadway Design be Used to Mitigate Air Quality Impacts from Traffic?; EM August 2009, p. 6. 2. Traffic-Related Air Pollution: A Critical Review of the Literature on Emissions, Exposure, and Health Effects; Preprint Special Report 17; Health Effects Institute, Boston, MA, 2009. 3. Heist, D.K.; Perry, S.G.; Brixey, L.A. A Wind Tunnel Study of the Effect of Roadway Configurations on the Dispersion of Traffic-Related Pollution; Atmos. Environ. 2009, 43, 5101–5111. 4. Finn, D.; Clawson, K.L.; Carter, R.G.; Rich, J.D.; Eckman, R.M.; Perry, S.G.; Isakov, V.; Heist, D.K. Tracer Studies to Characterize the Effects of Roadside Noise Barriers on Near-Road Pollutant Dispersion Under Varying Atmospheric Stability Conditions; Atmos. Environ. 2010, 44, 204-214. 5. Baldauf, R.W.; Thoma, E.; Khlystov, A.; Isakov, V.; Bowker, G.E.; Long, T.; Snow, R. Impacts of Noise Barriers on Near-Road Air Quality; Atmos. Environ. 2008, 42, 7502–7507. 6. Fujii, E.; Lawton, J.; Cahill, YT.A.; Barnes, D.E.; Hayes, C.; Spada, N.; McPherson, G. Removal Rates of Particulate Matter onto Vegetation as a Function of Particle Size; Final Report to the Breathe California of Sacramento Emigrant Trails Health Effects Task Force and Sacramento Metropolitan Air Quality Management District, 2008. 7. Cowherd, C., Jr. Transportability of Haul Road Dust Emissions in Open Pit Mines. In Proceedings of the 101st Annual Conference & Exhibition of the Air & Waste Management Association, Portland OR, June 2008. 8. Zhu, Y.F.; Hinds, W.C.; Kim, S.; Shen, S.; Sioutas, C. Study of Ultrafine Particles Near a Major Highway with Heavy-Duty Diesel Traffic; Atmos. Environ. 2002, 36, 4323-4335. 9. Buccolieri, R.; Gromke, C.; Di Sabatino, S.; Ruck, B. Aerodynamic Effects of Trees on Pollutant Concentration in Street Canyons; Sci. Total Environ. 2009, 407, 5247–5256. 10. Gromke, C.; Ruck, B. Influence of Trees on the Dispersion of Pollutants in an Urban Street Canyon—Experimental Investigation of the Flow and Concentration Field; Atmos. Environ. 2007, 41, 3287–3302. 11. Heisler, G.; Walton, J.; Yesilonis, I.; Nowak, D.; Pouyat, R.; Grant, R.; Grimmond, S.; Hyde, K.; Bacon, G. Empirical Modeling and Mapping of Below-Canopy Air Temperatures in Baltimore, MD and Vicinity. Presented at the Seventh Urban Environment Symposium of the American Meteorological Society, San Diego, CA, 2007. 12. Nowak, D.J.; Dwyer, J.F. Understanding the Benefits and Costs of Urban Forest Ecosystems. In Urban and Community Forestry in the Northeast; 2nd Edition; Kuser, J.E., Ed.; Springer: Dordrecht, 2007; pp. 25-46. 13. Bolund, P.; Hunhammar, S. Ecosystem Services in Urban Areas; Ecolog. Econ. 1999, 29, 293-301. 14. Brownson, R.C.; Baker, E.A.; Housemann, R.A.; Brennan, L.K.; Bacak, S.J. Environmental and Policy Determinants of Physical Activity in the United States; Am. J. Public Health 2001, 91, 1995-2003. 15. Frumkin, H. Beyond Toxicity: Human Health and the Natural Environment; Am. J. Prevent. Med. 2001, 20, 234-240. 16. Bell, J.F.; Wilson, J.S.; Liu, G.C. Neighborhood Greenness and Two-Year Changes in Body Mass Index of Children and Youth; Am. J. Prevent. Med. 2008, 35, 547-553. 17. Guite, H.F.; Clarke, C.; Ackrill, G. The Impact of the Physical and Urban Environment on Mental Well-Being; Public Health 2006, 120, 1117-1126. 18. Kuo, F.E.; Sullivan, W.C.; Coley, R.L.; Brunson, L. Fertile Ground for Community: Inner-city Neighborhood Common Spaces; Am. J. Community Psychol. 1998, 26, 823-851. 19.Wells, N.M. At Home with Nature: Effects of “Greenness” on Children’s Cognitive Functioning; Environ. Behavior 2000, 32, 775-795. 20. Takano, T.; Nakamura, K.; Watanabe, M. Urban Residential Environments and Senior Citizens’ Longevity in Megacity Areas: The Importance of Walkable Green Spaces; J. Epidemiol. Community Health 2002, 56, 913-918. 21. Moore, E.O. A Prison Environment’s Effect on Health Care Service Demands; J. Environ. Sys. 1981, 11, 17-34. 22. Fanning, D. Families in Flats; Brit. Med. J. 1967, 4, 382-386.