Toxic Air Pollution Hot Spots

These are the data files behind ProPublica’s “Sacrifice Zones” series. ProPublica analyzed five years of data from the EPA’s Risk Screening Environmental Indicators model to identify hot spots of cancer-causing industrial air pollution across the country. The model estimates concentrations of toxic chemicals near industrial plants in 810-by-810-meter squares of land, referred to as grid cells. ProPublica derived cancer risk estimates from the concentration numbers in the model’s grid cells, and averaged those estimates over a five-year period (2014-2018). At the time of publication, the data that ProPublica analyzed were the most recent available RSEI data.

After computing the average cancer risk estimates, we wrote an algorithm to identify toxic “hot spots,” defined as contiguous grid cells with an estimated incremental lifetime cancer risk greater than or equal to 1 in 100,000. That is, if a community of 100,000 people in the given area or grid cell were exposed to a toxic chemical continuously at the concentration provided in the RSEI data over a presumed lifetime of 70 years, roughly one additional individual might develop cancer from the exposure. That risk level is the exponential midpoint value in the EPA’s “fuzzy bright line,” a range of benchmarks for risks that the agency deems “acceptable.” The upper limit of this range was established in 1989, with the promulgation of emissions standards for the release of the chemical benzene as 1 in 10,000. At the low end of the range is 1 in 1 million.

The download available here includes a data dictionary, as well as two GeoJSON files and one CSV file:

  • One GeoJSON gives the grid cells — 810-by-810-meter squares — where cancer risk estimates are above 1 in 100,000. Contiguous groups of these grid cells make up the hot spots on our map. They also contain additional information, such as cancer risk estimates for each year of the five-year analysis period and population estimates.

  • The second GeoJSON contains the outlines of each of the hot spots identified by our analysis, with additional information such as the location of the hot spot and its area.

  • The CSV is a list of facilities that our analysis identified to be significant drivers of cancer risk in each of these hot spots.

For more detailed information on ProPublica’s analysis and the limitations of this data, please read our methodology.


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