Investigating Diesel Particulate Matter In California
Data Source: CalEnviroScreen 4.0, Office of Environmental Health
Hazard Assessment (OEHHA), California Environmental Protection Agency
(EPA), 2024
Background: CalEnviroScreen data combines social vulnerability data
(i.e. poverty, linguistic isolation, educational attainment) and
environmental exposure data (i.e. air pollution, water pollution,
proximity to hazardous waste sites) to compare the population-level
burden of Californian’s by census tract. The data is presented in
percentiles, and therefore represents relative comparisons between
cencus tracts. Diesel PM is classified as a carcinogen, or a
cancer-causing compound, by the International Agency for Research on
Cancer, and it is also associated with cardiovascular disease and
respiratory diseases, like asthma. Diesel PM is measured at various air
monitoring locations throughout the state operated by air districts, the
California Air Resources Board (CARB), and the Environmental Protection
Agency (EPA). CARB models the data to create 1 km x 1 km grids across
the state and the data is further adjusted by OEHHA within the EPA to
create percentiles by census tract.
Boxplot of Diesel Particulate Matter by California County
Bubble Chart of Poverty and Diesel PM
In an effect to identify whether there is a relationship between
poverty and Diesel PM, I used a Bubble graph below. You can visiually
see that many of the blue counties, particularly San Bernadino and San
Francisco, are burdened by experiencing higher percentiles of Poverty
and Diesel PM, indicating cumulative impacts. On the other hand, Ventura
county has high percentiles of Diesel PM (probably due to the 101
highway and other industry/ports in the area) yet has a very low Poverty
percentiles.
Diesel PM is not equally distributed throughout the state; people
living closer to industrial facilities, airports, ports, and highways
are disproportionately exposed.
Heatmap
Results: This interactive heatmap shows which areas experience
increased ambient exposure to Diesel PM. We can see from the box plot
and the map of California that some communities in the state have the
potential to be more highly exposed to Diesel PM than other communities.
The two most populated, urbanized counties in the state, Los Angeles and
San Francisco counties, contain more concentrated risk of Diesel PM,
with more census tracts in these counties in the higher Diesel PM
percentile categories than other more spread out or rural areas.
Additionally, counties in the Central Valley of the state, where air
pollution can get stuck in valleys are also disproportinately exposed to
Diesel PM, shown by higher Percentiles in these counties as well. What
this map does not convey are increased exposure risks due to
occupational exposure that some agricultural communities and workers
face. Therefore this data is just an estimate of exposure to ambient
Diesel PM, and may not characterize other sources that affect
individual, community, and public health. Additionally this data allows
us to make high-level, population-based comparisons, however, cities and
urban areas do not have equally distributed resources, greenspace nor
polluting infrastructure, therefore some residents of high percentile
census tracts will be more impacted than others.