TABLE 1—
PurpleAir Sensor Distribution and PM2.5 Concentrations by Population and Pollution Characteristics at Census Tract Level as of September 2020: California
| Characteristics | Deployed Sensors | Fully Operational Sensors | ||||
| None (n = 5824)a | 1–2 (n = 1667) | ≥ 3 (n = 544) | None (n = 6763) | 1–2 (n = 1171) | ≥ 3 (n = 101) | |
| Total population across the state, millions | 28.2 | 8.2 | 2.7 | 32.9 | 5.7 | 0.6 |
| CES score, 0–100 | 30.1 | 21.6 | 13.4 | 28.7 | 19.4 | 14.2 |
| Population characteristics in CES, mean | ||||||
| Asthma rate | 54.7 | 47.6 | 34.9 | 53.4 | 45.1 | 32.1 |
| Cardiovascular disease rate | 14.2 | 12.1 | 9.1 | 13.8 | 11.5 | 9.3 |
| Educational attainment, % | 20.3 | 11.9 | 6.7 | 19.1 | 10.1 | 7.1 |
| Poverty, % | 35.7 | 26.6 | 18.3 | 34.2 | 24.5 | 21.3 |
| Unemployment, % | 7.1 | 6.0 | 4.7 | 6.9 | 5.8 | 5.1 |
| Housing burden, % | 19.8 | 16.6 | 13.6 | 19.3 | 15.8 | 13.1 |
| Population characteristics score, 0–10 | 5.5 | 4.4 | 3.0 | 5.3 | 4.0 | 3.0 |
| Pollution burden indicators in CES, mean | ||||||
| Diesel PM, tons/year | 0.2 | 0.2 | 0.2 | 0.2 | 0.2 | 0.1 |
| Traffic impacts, vehicles/hour | 1153.7 | 1010.9 | 919.1 | 1135.3 | 970.1 | 899.5 |
| PM2.5 concentrations, µg/m3 | 10.6 | 9.2 | 8.2 | 10.4 | 9.1 | 7.9 |
| Pollution burden score, 0–10 | 5.3 | 4.7 | 4.2 | 5.2 | 4.6 | 4.4 |
| Race/ethnicity, % | ||||||
| Hispanic | 43.2 | 26.4 | 15.1 | 40.7 | 23.0 | 15.1 |
| Non-Hispanic White | 33.7 | 49.2 | 62.3 | 35.9 | 53.6 | 65.9 |
| African American | 6.1 | 4.5 | 2.9 | 5.9 | 4.1 | 1.9 |
| Native American | 0.3 | 0.6 | 0.4 | 0.4 | 0.7 | 0.8 |
| Asian American | 12.9 | 15.1 | 14.5 | 13.4 | 14.4 | 12.0* |
| Other/multiple | 2.9 | 3.8 | 4.5 | 3.1 | 3.9 | 4.1 |
Note. CES = CalEnviroScreen 4.0 version; n = the number of census tracts; PM2.5 = particulate matter with a diameter smaller than 2.5 µm; diesel PM = particle phase of diesel exhaust emitted from diesel engines. The total number of census tracts was n = 8035. Deployed sensors: sensors located within a census tract as of September 2020; fully operational sensors: sensors with readings meeting our completeness criteria (≥ 75%) between January 2020 and September 2020; asthma rate: age-adjusted rate of emergency department visits for asthma per 10 000; cardiovascular disease rate: age-adjusted rate of emergency department visits for heart attacks per 10 000; educational attainment: percentage of population older than 25 years with less than a high school education; poverty: percentage of population living below 2 times the federal poverty level; unemployment: percentage of the population aged > 16 years that is unemployed and eligible for the labor force; housing burden: percentage of low-income households and households severely burdened by housing costs.