Unrecognized volatile and semi-volatile organic compounds from brake wear

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Public Health

Background:

• Motor vehicles are significant sources of urban air pollution and greenhouse gases.
• The global transition to zero-emission vehicles (ZEVs) aims to reduce combustion-related emissions.
• Emissions from brake and tire wear are a persistent challenge, even for ZEVs.

Purpose of the Study:

• To identify and characterize previously unrecognized volatile and semi-volatile organic compounds emitted during vehicle braking.
• To assess the potential health and climate impacts of these novel brake emissions.
• To investigate nanoparticle formation during high-temperature braking events.

Main Methods:

• Analysis of gaseous emissions from simulated braking events.
• Chemical characterization of emitted volatile and semi-volatile organic compounds.
• Investigation of secondary pollutant formation potential and nanoparticle nucleation.

Main Results:

• Braking emits unrecognized volatile and semi-volatile organic compounds similar to biomass burning.
• Emissions include greenhouse gases, hazardous air pollutants, nitrogen-containing organics, nitrogen oxides, and ammonia.
• These compounds can form ozone and secondary pollutants; nanoparticle nucleation and growth observed at higher temperatures.

Conclusions:

• Brake wear emissions pose significant air quality and health risks, independent of tailpipe emissions.
• Specific compounds may serve as unique markers for brake wear.
• Disadvantaged communities and commuters are particularly vulnerable to these persistent emissions.