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 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.
The lead paint indicator is the percentage of occupied housing units built before 1960, calculated from
the U.S. Census Bureau’s ACS 5-year summary estimates on age of housing stock. EJScreen uses age of
housing stock as a surrogate for potential lead exposure as regulations banning lead-based residential
paint in 1978 led to the reduction and finally an end to the use of such paint in housing. The percentage
of older housing units is a proxy for potential exposure to lead paint and lead-containing dust that
accumulates indoors, in homes, or in other buildings where lead paint was used. EJScreen uses housing
units built before 1960.
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 PM 2.5 indicator is a measure of potential exposure to inhalable particles that are 2.5 micrometers or smaller. This is measured in terms of annual average concentration in air measured in micrograms per cubic meter. PM 2.5 information included in EJScreen highlights areas across the U.S. that are not meeting the national ambient air quality standard for PM 2.5. In other words, the levels of PM 2.5 present in these areas are deemed harmful to human health. The PM 2.5 indicator in EJScreen is a measure of potential exposure but not a measure of risk. The raw PM 2.5 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.
View in Map RoomLayer displays the modelled cancer risk associated with air toxics exposure. Figures represents the liklihood of hazardous exposure per 1 million population.
View in Map RoomLayer 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.
View in Map RoomLayer displays the locations of brownfield sites based on the September 2013 version of the EPA Assessment, Cleanup and Redevelopment Exchange System (ACRES) database.
View in Map RoomThis 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.
View in Map RoomThis layer displays the daily average concentration of ozone and the percentage of days with concetrations of ozone above the National Ambient Air Quality Standard (NAAQS) of 0.075 parts per million in 2015.
View in Map Room