Irvine, Calif., March 2, 2022 — Despite a significant increase in the number of low-cost air pollution sensors across the state, researchers from the University of California, Irvine have found that a smaller quantity were distributed in communities with lower socioeconomic status and higher proportions of racial/ethnic minority populations. They also discovered a lack of functioning air sensors in areas with greater levels of ambient fine particulate matter – where they are most needed. Fine particulate matter, or PM2.5, is known to increase the risk of adverse health effects, including asthma, cardiovascular diseases and adverse pregnancy outcomes.
This is the first study to examine the distribution and operation of PurpleAir low-cost sensors in relation to sociodemographic factors over multiple years across a large geographic region and to identify priority areas for future deployment. The findings are published online in the American Journal of Public Health.
“Although there was a substantial increase in sensor distribution during the widespread wildfires in 2020, only a very small number were placed by the South Coast Air Quality Management District and other agencies such as the California Air Resources Board. Most were set up by concerned citizens,” said corresponding author Jun Wu, Ph.D., professor of environmental and occupational health in UCI’s Program in Public Health. “Disadvantaged communities should be given access to PurpleAir sensors to fill in location gaps in air quality monitoring and address environmental justice concerns. Purchasing and distribution must be paired with regular maintenance to ensure their reliable performance.”
The researchers examined sensors’ spatial and temporal distribution and operation according to real-time PurpleAir data collected between July 2017 and September 2020 from more than 8,000 California census tracts. Social and economic factors were obtained from CalEnviroScreen 4.0, a mapping tool that uses environmental, health and socioeconomic information to calculate air pollution burden scores for every census tract in the state.
“The disproportionate exposure to PM2.5 is particularly concerning among communities of lower socioeconomic status and of color, as these groups are already at greater risk of developing preventable diseases,” said lead author Yi Sun, a UCI graduate student in environmental health sciences. “There is growing interest in understanding the inequitable distribution of PM2.5 and its impact on vulnerable populations.”
California is a state with a large, diverse population; a range of air pollution emission sources; and a relatively high density of low-cost sensor deployment compared to other regions in the U.S. and around the world. Study results can provide insight for future sensor development and deployment, especially in areas with vulnerable populations burdened by high air pollution exposures.
“On average, our findings show that more operational PurpleAir sensors are located in census tracts characterized by more affluence and lower disease rates, pollution burdens and percentages of Hispanic and African American residents,” Wu said. “On the other hand, our results indicated that there was less likelihood of sensor presence in census tracts with higher socioeconomic vulnerability, CalEnviroScreen scores, PM2.5 concentrations, and percentages of African American or Hispanic populations.”
The negative health effects of air pollution are among society’s most urgent environmental issues. Understanding sensor availability and operation is critical for future deployment programs to help ensure that communities of different income levels and ethnic backgrounds can be equitably served.
“Despite the encouraging findings that PurpleAir sensors expanded rapidly in California, there must be a concerted campaign to enhance community-based air quality monitoring, especially in disadvantaged communities,” Sun said. “Promoting the use of reliable low-cost sensors and sharing pollution data could help to strengthen awareness, education and action to reduce environmental injustice.”
Additional authors are Amirhosein Mousavi, Ph.D., formerly a postdoctoral research scientist at UCI; and Shahir Masri, Ph.D., assistant air pollution scientist in UCI’s Program in Public Health.
This study was supported by National Institute of Environmental Health Sciences grant R01ES030353.
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