California Air Resources Board

Non-combustion emissions such as brake and tire wear are becoming a larger percentage of roadway emissions due to increasing numbers of zero emission vehicles and the implementation of regulations to reduce tailpipe emissions in California. Brake and tire wear emissions are known to be a source for metals found in particulate matter (PM) in urban areas. Metal components in particles play an important role in the overall impacts of particles on health. Few comprehensive measurement studies have been performed on brake and tire wear PM-metals. In addition, few models are available to estimate exposures to PMmetals based on measured concentrations and these models are needed to provide exposure data to assess health effects in population-based studies. Therefore, this study was conducted to examine the PM-metal content of brake and tire wear by developing exposure models and studying the association with birth outcome related health impacts.   

The objective of this CARB funded study with UCLA researchers was to examine the health impacts of non-combustion emissions from brake and tire wear on birth outcomes in the Los Angeles area. The investigators examined metals that were linked to brake and tire wear emissions. They collected particulate samples for metals across the Los Angeles Metropolitan area and developed metal exposure models. These exposure models were used to estimate associations with birth outcomes by examining all births in Los Angeles for three years. The study found strong relationships between birth outcomes including Pre-Term Birth and Term Low Birth Weight and exposures to metals from brake wear (barium) and tire wear (zinc). Hispanic and African American mothers had higher odds of preterm delivery. Suggestive effects were found for placental abnormalities such as placental weight with exposures to metals.

Inflammation is a well-known mechanism for the health impacts of air pollution exposure. Measurements of how much oxidative stress a particle can produce is a way of measuring how much inflammation can be produced by particles. Research has found that an increase in oxidative stress potential for particles can be used to determine the strength of the adverse health effects caused by PM. Linking the oxidative stress data collected in this study with CalEnviroScreen data revealed a disproportionate burden of oxidative potential of particles for people in lower socioeconomic status groups in the Los Angeles air basin. Residents living in the most disadvantaged communities were exposed to particles with about 62% higher oxidative stress potential compared to people in the least disadvantaged communities. The result indicates that these disadvantaged communities would have greater impacts on their health from exposure to these particles.

Little information or research has been conducted on the health impacts of non-combustion emissions from brake and tire wear and this is the first study in California to examine the health impacts from these exposures. This work adds important scientific understanding to the adverse health effects of exposure to metals from brake and tire wear on the health of Californians and will help CARB better understand disparity in disadvantaged communities and target regulations to reduce associated health impacts.

Date:               April 10, 2023
Time:               2 – 4 pm
Location:          Zoom                                                         

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Background

With increasing market share of zero emission vehicles in California and reductions of tailpipe emissions, non-combustion sources have become the dominating source of traffic emissions. Non-combustion sources of traffic emissions include brake and tire wear.  Emissions studies have been conducted on vehicular non-combustion emissions through various study designs, including ambient measurements, laboratory modeling, and on-road sampling.Studies have been conducted on the metal contents and size distribution of brake and tire wear particles dispersed in the near-road environment. It is important to reassess these emissions as the vehicle fleet changes. However, no study has been conducted to examine health impacts from brake and tire wear PM metals.

This study examined the distribution of PM metals associated with brake and tire wear and their ability to produce oxidative stress in the body and used this information to model PM metals and determine their association with birth outcomes and placental health outcomes in the Los Angeles area using health data funded by other sources. Health effects studies included placental abnormalities and function and birth outcomes in an ongoing NIH-funded study of 161 pregnant women in Los Angeles and pre-term births and low birth weight in 285,614 live births in Los Angeles County from 2017-2019 from publicly available data.

Biography

Dr. Michael Jerrett, is an internationally recognized expert in Geographic Information Science for Exposure Assessment and Spatial Epidemiology. He is a full professor in the Department of Environmental Health Science, and Director of the Center for Occupational and Environmental Health at UCLA’s Fielding School of Public Health. Dr. Jerrett earned his PhD in Geography from the University of Toronto. Over the past 23 years, Dr. Jerrett has researched how to characterize population exposures to air pollution and built environmental variables, the social distribution of these exposures among different groups, and how to assess the health effects from environmental exposures. He has worked for many years on how the built environment affects exposures and health, particularly the role of parks and green spaces on physical activity promotion and obesity prevention. He has published extensively on climate change, including wildfires, vulnerability to heat stress, and public health co-benefits of climate mitigation. He serves as a standing member of the Health Effects Institute Review Committee, as an editorial board member for the Annual Review of Public Health, and he recently completed a 3-year term on the Geographical Sciences Committee of the U.S. National Academy of Science.