EJ Screening Index (EJScreen-Style)

It means the location scores higher than that share of comparison areas on a combined measure of environmental burden and demographic vulnerability. A 95th-percentile block group, for instance, scores above 95 percent of block groups nationwide on the combined EJ index for that environmental indicator. It does not mean residents face a measured level of exposure or a quantified health risk; the index is a relative screening score built to flag places for further study, not to estimate harm.

Multiplying enforces the intersectional logic of environmental justice: a place scores highly only when it has both elevated pollution and above-average vulnerability. Using the difference between local and national demographics means a place with average demographics contributes little regardless of pollution, and a vulnerable place with clean air also scores low. Adding the components would let a very high value on one dimension mask a low value on the other, which would defeat the purpose of identifying the overlap of burden and disadvantage.

No, not on its own. EPA is explicit that EJScreen is a screening tool meant to identify areas that may warrant further consideration, not a basis for final determinations about exposure, risk, or compliance. The percentile scores are relative, depend on modeling choices such as weighting and thresholds, and inherit the limits of the underlying data. Responsible use treats a flag as the start of a closer analysis that brings in finer exposure data, local knowledge, and other evidence before any decision is made.