Office of Transportation and Air Quality
EPA-420-F-21-064
October 2021
Best Practices for Reducing Near-Road
Pollution Exposure at Schools: Case Studies
Building Design and Operation Strategies for Reducing
Near-Road Pollution Exposure
Ventilation, Filtration, and Indoor Air Quality in Schools
Pilot study of high-performance air filtration for classroom applications
Southern California, United States
Summary: This study investigated the effectiveness of three air purification systems in reducing
exposure to air pollutants inside nine classrooms in southern California schools. The
authors measured concentrations of ultrafine particles (UFPs), particles that are
2.5 microns or less in diameter (PM2.5) and particles 10 microns or less in diameter (PM10),
black carbon (BC), and volatile organic compounds (VOCs, gases). The three tested
systems were an HVAC-based high performance panel filter, a register-based air purifier,
and a stand-alone air cleaning system. They found that a combination of the HVAC-based
high performance panel filter and the register-based air purifier were the most effective
solution and lowered BC, UFPs, and PM2.5 by an average of 87-96%. All three methods
resulted in improved air quality over preexisting conditions, and the HVAC-based high
performance panel filter alone reduced levels by almost 90%. The performance of the
register-based air purifier and standalone unit to remove VOC gas was inconclusive, and
more work is needed to determine this system's effectiveness for gas removal.
Link: https://onlinelibrary.wiley.com/doi/abs/10.1111/ina.12013
The impact of particle filtration on indoor air quality in a classroom near a highway
Amsterdam, Netherlands
Summary: PM10, PM2.5, and BC concentrations were measured inside a classroom and outside the
school building at a school in Amsterdam to determine the effectiveness of an upgrade to
the school's ventilation system to a fine F8 (MERV-14) filter, and how well it improved air
quality for students. During school hours, the upgraded filter reduced BC exposure by an
average of 36%, PM10 by 34%, and PM2.5 by 30%. The researchers concluded that using a
fine particle filter in a mechanical ventilation system can reduce classroom exposure to
traffic pollution. However, the filters must be frequently replaced and properly maintained
to ensure effective filtration.
Link: https://onlinelibrarv.wilev.com/doi/abs/10.1111/ina.12308
*>EPA
United States
Environmental Protection
Agency
1

-------
Filtration effectiveness of HVAC systems at near-roadway schools
Las Vegas, Nevada, United States
Summary: BC and gas-phase pollutants (benzene and 1,3-butadiene) were measured in three
classrooms at a school near a busy roadway in Las Vegas, Nevada. To assess the
improvement in pollution reduction, the researchers monitored concentrations before and
after the HVAC filtration was upgraded. The results show that before the HVAC upgrade,
31-66% of BC was removed by the filtration system. After the upgrade, indoor BC levels
were reduced by 74-95% relative to outside concentrations. However, gaseous pollutant
levels were higher indoors than outdoors by a magnitude of 1 to 2. The researchers state
a possible reason for the elevated gas-phase pollutant levels is indoor sources of benzene
and 1,3-butadiene.
Link: https://doi.orq/10.1111/ina.12015
Effectiveness of using enhanced filters in schools and homes to reduce indoor exposures to PM2.5
from outdoor sources and subsequent health benefits for children with asthma
Detroit, Michigan, United States
Summary: This study investigated the exposure levels, health benefits, and costs associated with
using high efficiency filters in homes and schools, especially with respect to asthma.
MERV-5, 8, 12, and 14 filters were compared. The results showed that replacing the lower
efficiency filters (MERV-5 and MERV-8) in schools with higher efficiency filters would
reduce the PM2.5-related asthma burden of children by 13% annually. Higher benefits are
estimated for higher efficiency filters. They calculate that the average cost to implement
the increased filtration is $63 per classroom, or $32 per child with asthma per year. They
conclude that using more efficient filters is a potentially cost-effective way to reduce the
asthma-related health burden for children.
Link: https://doi.org/10.1021/acs.est.8b02053
High-efficiency air cleaning reduces indoor traffic-related air pollution and alters indoor air
chemistry in a near-roadway school
Portland, Oregon, United States
Summary: This study investigated the impact of upgrading an air-cleaning system at a school
adjacent to a major highway. They installed MERV-8 and MERV-16 particle filters as well as
gas-phase filters and assessed the improvements in air quality. The gas phase filters were
chosen to remove NO2 and benzene, toluene, ethylbenzene, and xylenes (collectively
called BTEX). The results show that over eight months of monitoring, NO2 was reduced by
up to 96% and BTEX gases were reduced by over 80%.
Link: https://doi.org/10.1021/acs.est.0c02792
2

-------
Influence of combined dust reducing carpet and compact air filtration unit on the indoor air
quality of a classroom
Gelderland, Netherlands
Summary: Particulate matter (PM10 and PM2.5), gases (VOCs, nitrogen dioxide [NO2], and
formaldehyde), and other traffic-related pollutants were measured in two primary school
classrooms equipped with compact air filtration systems. During school hours, PM2.5 and
PM10 were reduced by 27-43% compared to a classroom without the air filtration system.
On weekends, the reductions observed were 51-87%. Because levels of VOC were low, the
effectiveness of the interventions used to remove VOC concentrations was inconclusive.
Link: https://doi.ora/10.1039/C4EM00506F
Site-Related Strategies for Reducing Near-Road Pollution
Exposure	
Transportation Policies: Anti-Idling Campaigns
The impact of an anti-idling campaign on outdoor air quality at four urban schools
Cincinnati, Ohio, United States
Summary: The goal of this work was to assess the impact of an anti-idling campaign on outdoor air
quality at four schools that experience different degrees of automobile and bus traffic. The
research team measured PM2.5, elemental carbon, and particle count at each school for 5
days before and after the implementation of an anti-idling campaign. They also took
simultaneous measurements at four community sites to determine background levels,
which were subtracted from the measurements taken at the nearby school. After
implementing an anti-idling campaign, the school with the most bus traffic (39 buses) saw
a decrease in PM2.5 concentrations from 4.11 |ig/m3 to 0.99 |ig/m3, a decrease in
elemental carbon from 0.40 |ig/m3 to 0.15 |ig/m3, and a decrease in particle number
concentration from 11,560 particles per cm3 to 1,690 particles per cm3. Schools with fewer
buses (5 to 11) did not realize a significant reduction in pollutants. The authors concluded
that anti-idling campaigns are effective for schools that have significant bus and
automobile traffic.
Link: https://pubs.rsc.ora/en/content/articlelandina/2013/em/c3em00377a
3

-------
Roadside Barriers: Vegetation
Impact of green screens on concentrations of particulate matter and oxides of
nitrogen in near road environments
Kensington and Chelsea, United Kingdom
Summary: To establish the efficacy of vegetative barriers in reducing road pollution at schools, an ivy
screen was installed along the perimeter of a playground at a primary school in the UK.
Oxides of nitrogen (NOx) and PM10 were measured on either side of the screen, and the
difference in the concentration between the roadside and playground side was assessed
as the ivy matured. The results show that the screen was an effective pollution barrier
once the ivy had started growing, and significant reduction in pollution could be seen
once the screen had matured. The ivy screen led to an overall decrease in the pollution
concentrations on the playground side of the screen by 24% for NO2 and 38% for PM10.
During school hours specifically, when both emissions and exposure are highest, the
reductions were up to 36% for NO2 and 41% for PM10.
Link: https://www.londonair.org.uk/london/reports/GreenScreen Report.pdf
The association between greenness and traffic-related air pollution at schools
Barcelona, Spain
Summary: Traffic-related air pollutants, including NO2, PM2.5, BC, and PM10, were monitored inside
and outside of 39 schools across Barcelona. Satellite images were used to assess
greenness (the degree of vegetation coverage and green space) within and around (50 m
buffer) each school. Models were run to correlate the degree of greenness with traffic
pollutant levels. The study found that higher greenness within and around schools was
consistently associated with lower pollutant levels both outside and indoors. Further, the
results suggest stronger associations between schools with increased greenness and lower
outdoor pollution levels if a school was surrounded by more trees.
Link: http://www.sciencedirect.com/science/article/pii/S0048969715003782
4

-------