First, Second, and Third Tier Review of Toxic Air Pollutants
There are three levels of review for making permit decisions about projects that emit toxic air pollutants (TAPs):
This web site is intended for those seeking information about what to expect when they need a first, second, or third tier review for an air quality permit.
First tier: All projects must undergo first tier review (toxic screening) before getting a permit. This is required by WAC 173-460-040. The purpose of the toxic screening is to control emissions of TAPs from new sources in order to prevent air pollution, reduce TAP emissions as much as possible, and maintain healthy and safe air quality.
Second tier: If a project emits more of a listed TAP than is allowed by the Acceptable Source Impact Levels (ASIL) in Chapter 173-460 WAC, Ecology must perform a second tier review for that TAP. This review determines the increase in lifetime cancer risk and other health effects for persons exposed to increased amounts of the TAP as a result of the proposed project. The cancer and health risks are then compared to the maximum risk allowed by a second tier review to see if they are within allowable limits.
Third tier: If the emissions of a TAP result in a risk higher than allowed by the second tier review, a permit applicant may ask Ecology to perform a third tier review. A third tier review is a risk management decision made by Ecology. Ecology's Director decides whether the risk of the project is acceptable based on:
Please refer to WAC 173-460-150 for information on the chemicals that are TAPs.
Local air quality agencies and Ecology's regional offices routinely perform first tier reviews. Ecology's headquarters office performs all second and third tier reviews. Applicants must prepare a health impact assessment (HIA) for any project subject to second and third tier review. Ecology provides guidance on how to prepare the HIA.
Refer to Ecology's guidance document for this information.
For more information, please contact
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