Because there are no federal health standards for air toxics,
Oregon adopted air toxics benchmarks
designed to help focus pollution reduction efforts.
These benchmarks help DEQ identify, evaluate and address air
toxics problems. Oregon air toxics benchmarks are based on concentration levels that would
result in a cancer risk of one in a
million excess cancers based on a lifetime of exposure. For non-carcinogens,
levels you could breathe for a lifetime without any non-cancer health effects.
The ambient benchmark concentrations for 52 air toxics of concern in Oregon are based on consensus recommendations
from the Air Toxics Scientific Advisory Committee, a
panel that provides advice on the state air toxics program
that is scientifically and technically sound, independent and balanced.
The benchmark concentrations are based on levels that protect the health
of our most sensitive individuals. These benchmarks provide
consistent health-based goals, as DEQ develops strategies to
reduce air toxics. Benchmarks are expressed as micrograms of a specific toxic compound per cubic meter of air.
The Environmental Quality Commission unanimously adopted a new benchmark concentration for ethyl benzene and more protective benchmarks for lead and manganese at its
August 19, 2010 meeting. The benchmark for mercury was clarified
but the value unchanged.
In 2011, the DEQ Air Toxics Science Advisory Committee
will study whether the creation of a benchmark for short-term
exposures to air toxics provides a benefit to the air toxics program. DEQ's current benchmarks are based on health effects from long-term (lifetime) exposures.
Frequently Asked Questions (click to expand)
How does DEQ plan to assess health-effects from short-term exposures to air toxics?
DEQ has committed to investigate the benefit of adding benchmarks for shorter-term exposures to the DEQ Air Toxics Program.
DEQ's current benchmarks are based on health effects from long-term (lifetime) exposures to air toxics.
Benchmarks for shorter-term
exposures would apply in addition to the existing benchmarks for lifetime exposures.
DEQ would use benchmarks for shorter-term exposures to help evaluate
threats from air toxics and determine if additional emission reduction measures are needed to protect public health.
There are a number of technical,
policy and practical issues that DEQ must consider
to determine if and how to integrate short-term benchmarks into DEQ Air Toxics Program. These include:
- The availability and quality of toxicological information needed to set short-term benchmarks;
- Monitoring and modeling techniques needed to properly characterize short-term concentrations;
- The number of pollutants emitted in Oregon that would be at concentrations near or above potential short-term benchmarks and the frequency and duration of such concentrations;
- The potential for short-term concentrations to be lowered by the same emission reduction measures needed to reduce long-term concentrations; and
- The availability of resources for monitoring and implementation.
Developing the existing long-term
air toxics benchmarks took about two years,
and the evaluation of short-term benchmarks is likely to take a similar amount of time.
By mid 2011, DEQ plans to begin the evaluation by discussing the technical issues involved with short
term benchmarks with DEQ's Air Toxics Science Advisory Committee. After receiving
technical input from that committee, DEQ may form a policy
advisory committee to discuss if and how
short-term benchmarks would be incorporated into DEQ's program. Following that, DEQ would draft a rulemaking proposal
for public comment and consideration by the Environmental Quality Commission.
One significant challenge is that DEQ lacks air toxics
monitoring results for periods shorter than 24 hours, which makes it difficult to
assess whether there would be adverse health effects from shorter exposures.
However, there is one early indication that short-term concentrations may be
below levels associated with acute health effects. In conducting a field test of
monitoring equipment in the summer of 2008, Cooper Environmental Services collected hourly concentrations
of manganese and other metals immediately downwind of the ESCO foundry in Northwest Portland.
The highest concentration Cooper measured in one hour was about 30 times lower than a published acute
health effect concentration for manganese.
(An acute concentration is one that may be exceeded for
one hour every two weeks without causing irreversible health problems.)
On the other hand, manganese concentrations measured in Cooper’s pilot study may not meet the eight-hour reference
exposure level used in California.
(Eight-hour reference exposure levels are concentrations at or below which
adverse health effects are not likely to occur in the general human population with intermittent exposures of
eight hours per day, up to seven days per week.
As a precautionary measure, the reference exposure level
for manganese is set at a level 300 times below the no-observed-effect-level.)
DEQ will need additional monitoring and modeling to better assess any potential threats
from short-term exposures to manganese and other air toxics.
While the evaluation of short-term benchmarks
is occurring, DEQ will continue to implement Oregon's
current program to reduce air toxics. DEQ’s current air toxics benchmarks are set at
levels that would prevent non-cancer health effects and result in a very minimal
risk of cancer over a lifetime of exposure. By comparing the current benchmarks
to annual average monitored or modeled concentrations of air toxics, DEQ has
determined that air toxics concentrations exceed the
benchmarks in every Oregon county. To address this,
DEQ developed a number of emission reduction measures to reduce
exposure to air toxics DEQ currently is developing additional state-wide
and Portland-specific measures. DEQ expects to make significant progress in
protecting public health from air toxics risks through these efforts.
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