The Health Effects Institute (HEI) has launched two new studies funded under RFA 21-1, Quantifying Real-World Impacts of Non-Tailpipe Particulate Matter Emissions. Emissions from automobile exhaust systems have decreased in recent years due to the introduction of cleaner fuels and new control technologies on internal combustion engines, as well as increases in numbers of hybrid and electric vehicles.

However, emissions from the use and wear of brakes, tires, and other non-tailpipe sources are gaining interest from researchers and regulators because non-tailpipe sources now contribute a higher fraction of the particulate emissions from motor vehicles.

These two new studies will measure mass and composition of ambient particles from non-tailpipe motor vehicle sources and assess the effects of such emissions on air quality, human exposure, and human health.

Research teams will also measure concentrations of exhaust pollutants in an attempt to disentangle non-tailpipe and tailpipe pollution, to better understand how each effects human health. The new studies are:

Improved Characterization of the Real-World Contributions and Impacts of Non-tailpipe Particulate Matter Emissions,” led by Greg Evans, University of Toronto. This study will measure concentrations of non-tailpipe (NTP) particulate matter across Toronto, Canada to determine how much non-tailpipe pollution people might breathe in everyday life and how to better measure these exposures in the future.

The three-year study will focus on real-world field measurements to yield methods, data and knowledge needed to estimate and understand population exposure to non-tailpipe (NTP) vs. tailpipe (TP) particulate matter (PM), by addressing four overarching questions:

• What combination of methods can best characterize NTP emissions?

• What is the contribution of NTP emissions to ambient PM in large, high traffic cities?

• Do NTP and TP emissions vary spatially and temporally in ways that manifest distinguishable population exposure patterns?

• Are the differences in the mass concentrations of PM between NTP and other sources, within cities, or among hot spot microenvironments, sufficient to enable future studies to assess the health risk of real-world NTP exposures?

The project will be executed as four integrated sub-studies. Investigation of the temporal patterns of NTP emissions will identify the chemical profiles of NTP PM from brakes, tires, and road dust. The spatial patterns of NTP and TP PM across the Greater Toronto Hamilton Area will be characterized using three separate approaches: saturation studies, mobile sampling, and a sensor network.

Here, physical and chemical methods will be used to distinguish and constrain the relative contributions of different NTP sources. Samples generated through this field work will be characterized though lab analysis, which will also further refine the chemical and physical profiles of the NTP sources. Moreover, the oxidative potential (OP) of NTP PM will be determined and compared with the OP of ambient PM samples.

Finally, the methods developed and evaluated through these sub-studies will be applied to identify and characterize NTP hot spots. The team will then synthesize this new knowledge to evaluate the feasibility of conducting future studies to assess the impacts of NTP exposure on health.

“Assessing the Impact of Non-exhaust Emissions from Traffic on the Asthmatic Airway (IONA),” led by Chris Griffiths, Queen Mary University of London. In this study, participants with mild to moderate asthma will ride stationary bicycles on sidewalks in three London, UK environments (busy road characterized by stop-and-go traffic, high speed continuous traffic, and urban background) to measure how exposure to traffic with different mixtures of non-tailpipe and tailpipe emissions affects lung function of asthmatic adults.

Previous in vitro studies on dendritic cells and airway macrophages indicated enhanced immune responses, consistent with a worsening of asthma symptoms, with the coarse particulate fraction (PM_2.5-10) of urban air, a fraction known to be enriched with non-tailpipe constituents.

People with asthma represent a major vulnerable group. Asthma is globally the most prevalent long-term condition, strongly impacted by air pollution, affecting adults and children, with major morbidity disproportionately affecting disadvantaged and minoritized ethnic populations. The asthmatic airway provides an exquisitely sensitive model to assess health impacts of non-tailpipe emissions.

To date, no research has explored whether real-world NTP emissions are causally related to worsening of asthma. The new study aims to:

• Deliver the first study to quantify the acute airway responses of asthmatics to NTP emissions under realworld urban conditions

• Establish a source apportioned time series of PM_2.5 and PM₁₀, including of NTP and TP emissions, at key selected London trial sites.

• Examine the relationship between exposure to NTP and TP emission estimates of the airway dose following exposure.

• Define the relationship between NTP PM and the induction of Th2 and Th17 type inflammation in the asthmatic airway.

• Establish a bio-bank of samples to support future HEI-sponsored research in this area.

HEI. The Health Effects Institute is a non-profit corporation chartered in 1980 to provide high-quality, impartial, and relevant science on the health effects of air pollution. HEI receives balanced funding from government and industry. Other public and private organizations periodically support special projects or certain research programs.

HEI’s research program has addressed many important questions about the health effects of a variety of ambient air pollutants over the past two decades. These include carbon monoxide, ozone, particulate matter, and nitrogen oxides, which are regulated in the United States by the National Ambient Air Quality Standards (NAAQS).

In addition, many air toxics and fuel additives have been studied, including methanol, diesel exhaust and associated compounds, benzene, 1,3-butadiene, aldehydes, and oxygenates added to gasoline.