New maps showing domestic well use for drinking water! The quality and safety of water from domestic wells are not regulated by the Federal Safe Drinking Water Act or, in most cases, by state laws. Instead, individual homeowners are responsible for maintaining their domestic well systems and for monitoring water quality. Well use data is modeled by the EPA using the 1990 decennial census and records from drillers in the time since to determine the estimated number of wells in use in a given area. The 1990 long-form version of the Census was the last time a comprehensive national survey was taken on where people were obtaining household domestic water. The current uses are estimated using a machine learning algorithm in conjunction with this survey data and drilling records to estimate the percent of housing units using wells at the edges of public water systems.
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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.
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This US EPA feature layer is updated hourly and reflects the latest hour of air quality data received from each monitoring site that reports to AirNow. The concentration and AQI values are for Ozone and Particulate Matter (PM) only. Air quality index ranges from 0-5,000 with higher values indicating worse air quality.
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This layer displays the daily average concentration of ozone and the percentage of days with concentrations of ozone above the National Ambient Air Quality Standard (NAAQS) of 0.075 parts per million in 2017.
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This layer displays the daily average concentration of ozone and the percentage of days with concentrations of ozone above the National Ambient Air Quality Standard (NAAQS) of 0.075 parts per million in 2018.
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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
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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.
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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.
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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.
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This layer displays the daily average concentration of fine particulate matter and the percentage of days with concentrations of fine particulate matter above the National Ambient Air Quality Standard (NAAQS) of 35.0 micrograms per cubic meter in 2018.
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