The Superfund proximity indicator is reflective of the total count of sites proposed and listed (final) on
the National Priorities List (NPL) in each block group within 5 km of the average resident in a block
group, divided by distance, calculated as the population-weighted average of blocks in each block group.
The air toxics respiratory HI indicator is the respiratory HI from the analyzed carcinogens in ambient
outdoor air, as provided by the 2017 Air Toxics Data Update. The data is reported at the Census tract
level. Block group level values are assigned by repeating each parent tract level value.
The air toxics cancer risk indicator is the estimated lifetime inhalation cancer risk from the analyzed
carcinogens in ambient outdoor air, as provided by the 2017 Air Toxics data Update. The value of the
indicator is persons per million lifetime. The data is reported at the Census tract level. Block group level
values are assigned by repeating each parent tract level value.
The ozone indicator in EJScreen reflects potential ozone exposure measured in terms of summer
seasonal daily average maximum concentrations in an 8-hour period measured in parts per billion.
Ozone information included in EJScreen highlights areas across the U.S. that are not meeting the
national ambient air quality standard for ozone. In other words, the levels of ozone present in these
areas are deemed harmful to human health.
The ozone indicator in EJScreen is a measure of potential exposure but not a measure of risk. The raw
ozone data is compiled by census tract, which is supplied for use in the tool by EPA’s OAQPS. For air
toxics risk measures (as opposed to exposure) users can turn to EJScreen’s other three indicators: cancer
risk, respiratory HI, and diesel PM.
The UST indicator quantifies the relative risk of being affected by a LUST for a block group. The indicator
is derived by the weighted sum of active LUSTs and sum of active and temporarily out of service USTs
within a certain distance from a block group.
The RMP facility proximity is reflective of the total count of RMP facilities in each block group within 5
km of the average resident in a block group, divided by distance, calculated as the population-weighted
average of blocks in each block group