Aclima has updated air.health to reflect our use of improved calculations for analyzing and mapping the data we measured over a one year period for each county from 2019-2020. This data is now modestly different from data in the first version of this public tool, released in May 2022.

The underlying 1-Hz, or 1-second, data as collected by the vehicles has not changed. However, data products, such as pollution averages at the road segment and hexagon scale, have changed modestly. In the map, that means the color of a road segment or hexagon may have slightly changed from the first version.

We identified a bug in our data-processing calculations that was causing a small number of road segments to be excluded from PM

 averages. We fixed this bug, resulting in the hexagon-level averages to change by a very small amount.

We implemented another minor bug fix in our PM

We applied the same aggregation model to our CO

 data. Our model is carefully curated to ensure hyperlocal pollution variation is most accurately displayed.

Overview of changes and impacts on the report:

 averages changed by approximately 0.1 to 0.2 µg/m

 (1 to 2%) across all Bay Area counties. Because some of these changes were positive while others were negative, these changes largely cancel each other out. As a result, the overall county-level averages changed very slightly (on average 0.006 µg/m

). For instance, the smallest change was by an average of 0.0003 µg/m

, or 0.004%, in Contra Costa County, and the largest was by an average of -0.037 ug/m

 averages changed modestly in San Francisco (typical change of 0.7 µg/m

, or 9%), and Contra Costa Counties (typical change of 0.6 µg/m

 averages changed by approximately 0.4 to 0.8 ppm (0.1 to 0.2%) across all Bay Area counties. Because some of these changes were positive while others were negative, these changes largely cancel each other out. As a result, the overall county-level averages changed very slightly (on average 0.12 ppm). For instance, the smallest change was by 0.01 ppm, or 0.002%, in Napa and Solano Counties, and the largest change was by an average of 0.158 ppm, or 0.04%, in San Mateo County.

San Francisco Bay Area

-equipped vehicles to map air pollutants and 

 on every publicly accessible road in all nine Bay Area counties.

 are few and far between. What’s more, GHG measurements are rarely captured in cities and are limited in scope when they are available. 

 maps at the neighborhood block level, where 

 can vary up to 800% from one block to the next.

Aclima’s county-wide area air quality maps

aclima

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