25 May 2023

EJ Screen Ozone

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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.

25 May 2023

EJ Screen Diesel Particulate Matter

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The Diesel PM indicator is the estimated concentration of Diesel PM as provided by the 2017 Air Toxics
update. The value of the indicator is in μg /m3
, and reported at the Census tract level. Block group level
values are assigned by repeating each parent tract level value.

25 May 2023

EJ Screen Air Toxic Cancer Risk

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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.

25 May 2023

EJ Screen Air Toxic Respiratory Risk

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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.

25 May 2023

EJ Screen Traffic Proximity

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The traffic proximity indicator is based on AADT count divided by distance in meters from the Census
block centroid. The proximity score is based on the traffic within a search radius of 500 meters (or
further if none is found in that radius). This distance was selected to be large enough to capture the
great majority of road segments (with traffic data) that could have a significant impact on the local
residents, balanced against the need to limit the scope due to computational constraints. The closest
traffic is given more weight, and the distant traffic is given less weight, through inverse distance
weighting. For example, traffic 500 meters away is given only one tenth as much weight as traffic 50
meters away.

27 Oct 2022

Air Toxics – Cancer Risk by Census Tract

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Layer displays the modelled cancer risk associated with air toxics exposure. Figures represents the liklihood of hazardous exposure per 1 million population.

27 Oct 2022

Air Toxics – Non-Cancer Risk by Census Tract

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Layer displays the modelled non-cancer risk associated with air toxics exposure. A hazard index (HI) of 1 or lower means air toxics are unlikely to cause adverse noncancer health effects over a lifetime of exposure.

22 Sep 2022

Brownfield Sites

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Layer displays the locations of brownfield sites based on the September 2013 version of the EPA Assessment, Cleanup and Redevelopment Exchange System (ACRES) database.

15 Apr 2021

EPA RSEI Score, 2019

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This layer displays RSEI score by county. A RSEI Score is a unitless value that accounts for the size of the chemical release, the fate and transport of the chemical through the environment, the size and location of the exposed population, and the chemical’s toxicity. RSEI scores are designed to be compared to each other. A RSEI Score 10 times higher than another RSEI Score suggests that the potential for risk is 10 times higher. Relatively small releases may lead to high RSEI Scores if the toxicity weight is particularly high or if the estimated exposed population is large. Conversely, large releases may lead to low RSEI Scores if the toxicity weight is low or if the estimated exposed population is small. A low RSEI Score indicates low potential concern from reported TRI releases, but other kinds of environmental risk may also be present, including pollution from mobile sources like cars and trucks, hazardous waste, and unreported releases from facilities.