Guidelines for Developing ESLs, ReVs, and URFs (RG-442)
What are Effects Screening Levels?
Effects Screening Levels are used to evaluate the potential for
effects to occur as a result of exposure to concentrations of
constituents in the air. ESLs are based on data concerning health
effects, the potential for odors to be a nuisance, effects on
vegetation, and corrosive effects. They are not ambient air
standards. If predicted or measured airborne levels of a
constituent do not exceed the screening level, adverse
health or welfare effects are not expected. If ambient levels of
constituents in air exceed the screening levels, it does not
necessarily indicate a problem but rather triggers a review in more
depth.
Both short- and long-term ESLs are listed.
“Short-term” generally indicates a one-hour averaging
period. Exceptions are noted parenthetically after a constituent
name. “Long-term” indicates an annual averaging period.
One asterisk immediately after the constituent name signifies that the ESL is currently under review and thus subject
to change. Two asterisks after the constituent name indicate
that the constituent has disaster potential.
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