Surviving the Ills of Freeway/Interstate Pollution

After reading the Los Angeles Times article entitled "Proposed state law seeks to ban freeway expansions in underserved communities" in full, we understand what California Assemblywoman Cristina Garcia (D-Bell Gardens) is seeking to accomplish. Within the article Miami is mentioned as having a community becoming the victim of freeway expansion and within the comment section it was mentioned that citizens successfully defeated a freeway expansion in the Beverly Hills area in the 1970s. 

With all that being said we wondered if North Carolina had something similar occur in the 1960s - 70s, but even moreso we wanted to explore and share what can be done from a site development standpoint to reduce the ills of air pollution, noise pollution, and all the negative health effects derived from living near freeways.

Within this article we have listed recommendations and solutions from various sources when it comes to site development and reducing the negative impact that freeway or interstate pollution can have on occupants inhabiting nearby structures and public spaces. Additional bonus information included as well.

"She said state leaders should consider the significant evidence of racial and health disparities caused by highway construction as well as research showing that freeway widenings frequently fail to resolve traffic congestion because they induce more car trips.

“If we have the data and we have the research and we’re ignoring it, that’s when it starts to become criminal when you’re in a position of power,” Garcia said." - LA Times

Those health disparities mentioned by California Assemblywoman Cristina Garcia have been documented in detail by the American Lung Association in their article entitled "Highway Air Pollution and Your Health: Six Things You Need To Know"; For example stating that "emerging research warns that traffic pollution may cause the onset of new asthma, cause cognitive problems and harm prenatal development".

Furthermore here is an abstract found at the National Center for Biotechnology Information website entitled "Minimizing Air Pollution Exposure: A Practical Policy to Protect Vulnerable Older Adults from Death and Disability" where it is stated that "Air pollution causes an estimated 200,000 deaths per year in the United States alone. Older adults are at greater risk of mortality caused by air pollution.".

And this is what the County of Los Angeles Public Health Department said on the issue in their recommendation report "Studies indicate that residing near sources of traffic pollution is associated with adverse health effects, including development of asthma in children, more severe symptoms among those with asthma, non-asthma respiratory symptoms, impaired lung function, reduced lung development during childhood, and cardiovascular disease morbidity and mortality"

Listed below are Strategies to Reduce Air Pollution Exposure Near Freeways/Interstates or what the California Air Resources Board calls "High-Volume Roadways"

What the EPA or Environmental Protection Agency and County of Los Angeles Public Health Department have to say:

Vegetation

"Trees and plants along roadways can reduce particle concentrations by acting as a physical barrier between roadways and schools (similar, in effect, to sound walls), or by filtering particles as they pass through and accumulate on leaf surfaces. The amount of removal depends on season, plant species, leaf size and density, and pollutant type."

Roadside vegetation which is most effective when the barriers are thick, with full coverage from the ground to the top of the canopy, and extend or wrap around an area, so that pollutants cannot flow around the edges

Vegetation barriers which when done properly remove some of the smallest particulate pollutants from the near-road environment

Key Factors in Having an Effective Roadside Vegetation Barrier

1. Use an evergreen species with mature, dense greenery (at least 20 feet thick)
2. Locate the barrier downwind and close to the
   roadway
3. Choose species appropriate for the region and
   site (Consult with plant nurseries, local
   cooperative extensions, city governments,
   the U.S. Forest Service, etc.)
4. Density of the greenery
5. Height of the greenery
6. Located close to the pollutant source
7. When wind speeds are low (we are curious how locations such as Chicago, IL handle this)
8. Vegetation should be appropriate for the location of interest, including water requirements, non-invasive species, and aesthetics
9. Vegetation should maintain its structure during all seasons, therefore coniferous trees would be preferable to hardwood species
10. Vegetation types chosen should also not be emitters of air pollution or high levels of pollen
11. Vegetation should be sited consistent with state and local safety guidelines
12. In selecting the design and species for this vegetation barrier, follow guidance described in the Environmental Protection Agency’s July 2016 document “Recommendations for Constructing Roadside Vegetation Barriers to Improve Near-Road
    Air Quality”. Identify appropriate trees using the following resource> www.itreetools.org 
13. Plant additional trees on neighborhood streets surrounding the housing development to further mitigate air pollution

Sound Walls/Roadside Barriers

"Pollutant concentrations behind a barrier located downwind of a roadway are typically lower than concentrations in the absence of a barrier. Studies show that reductions in downwind pollutant concentrations within approximately 500 feet of a highway in the presence of a well-designed sound wall can be on the order of 15% to 50%."

Key Factors in Having an Effective Sound Wall

1. Roadway configuration
2. Local meteorology
3. Barrier height, design
4. Endpoint location (no gaps)

Roadside vegetation + Sound Walls/Roadside Barriers

"The combined use of vegetation and sound walls has shown promise in reducing vehicle pollution downwind of roadways by up to 60%"

To be most effective applying roadside vegetation and noise barriers together greatly reduces downwind pollution at a greater rate than vegetation or a solid, noise barrier would do if used separately

Additional benefit of the above include water runoff control; The above strategies were recommended to help support two communities an elementary school in Oakland, California, and a community park in Detroit, Michigan that were selected based on their proximity to major roadways with significant diesel traffic

Buffer Zone Requirements 

Private and public occupied buildings and public assembly spaces are not permitted to be within 2,500 feet of major roadways where explosives are carried and at least 1,500 feet from roads where gasoline, diesel, propane, chlorine, oxygen, pesticides, or other combustible or poisonous gases are transported; This comes from the California Department of Education School Site Selection and Approval Guide (2000), cited in the EPA Report - Table 2 at Page 5, but could be applied overall regardless of the occupancy classification of the structure. 

Also note that relief could be given to unoccupied structures within the buffer zone but the question would then be how far in the buffer zone should that unoccupied structure be allowed to be.

Take a look at the EPAs report on "Best Practices for Reducing Near-Road Pollution Exposure at Schools" (PDF) for more detailed information on effective strategies shown in general above

Bonus Additional  Information/Resources:

Aside from Site Development strategies, air filters used in buildings have shown to be effective! Give this article entitled "Air filters can scrub out pollutants near highways, reduce blood pressure" a read! 

Here is an abstract from AHA Journals entitled "Effect of Reducing Ambient Traffic-Related Air Pollution on Blood Pressure"

Here is another abstract entitled "Developing Community-Level Policy and Practice to Reduce Traffic-Related Air Pollution Exposure" that states the following as solutions:

"Community-level tactics for reducing exposure include the following:

1. HEPA filtration
2. Appropriate air-intake locations
3. Sound proofing, insulation and other features
4. Land-use buffers
5. Vegetation or wall barriers
6. Street-side trees, hedges and vegetation
7. Decking over highways
8. Urban design including placement of buildings
9. Garden and park locations
10. Active travel locations, including bicycling and walking paths"

Building Design Solutions that can be implemented by Architects and Engineers (from the County of Los Angeles Public Health Department recommendation report)

1. Site apartment units as far as possible from the source of air pollution
2. Double glaze all windows in the housing units to reduce exposure to air pollution
3. Avoid or limit the placement of balconies on the side of the building facing the freeway/high
   volume roadway
4. Install MERV 13 filters (or above) on the air handling units for the HVAC system and
   replace them on a quarterly basis or whatever basis is recommended by the filter/HVAC
   system manufacturer. Identify who will replace the MERV filters, ensure that personnel are
   trained on their responsibilities, and conduct regular inspections to ensure that filters are
   being replaced as recommended
5. Locate outdoor air intakes for the HVAC system as far as possible from the freeway/roadway,
   the freeway off-ramp, and the parking area
6. Maximize the sound transmission co-efficient (STC) for the interior/exterior walls to limit
   indoor noise and air pollution
7. Design buildings with varying shapes and heights to help break up air pollution emission
   plumes, increase air flow, and help reduce pollutants such as particulates and noise