Comment Period Extended – Proposed Short-Term Guideline Concentrations for Air Toxics 

Cleaner Air Oregon

Proposed Short-Term Guideline Concentrations for Air Toxics

In March of 2016 OHA rapidly developed a provisional set of 24-hour screening levels for airborne toxic heavy metals associated with art glass manufacturing in Portland. The time frame to develop these provisional values did not allow for external scientific peer review or public comment. The agencies are in the midst of an effort to expand upon the list of air toxics for which short-term guideline concentrations (SGCs) exist and to increase scientific confidence in the values used by agencies to compare short-term ambient air toxics monitoring results. The proposed SGCs are intended to replace and expand upon existing provisional 24-hour screening levels. They have already been reviewed by external scientific peer reviewers with expertise in toxicology, and their comments have been addressed in the draft we are now presenting for public comment.

This document contains proposed short-term guideline concentrations (SGCs) for 15 air toxics for which OHA and DEQ are seeking public comment. You can submit your comments by emailing until the end of the extended comment period, April 14, 2017.

These SGCs are intended to replace and expand upon the provisional 24-hour screening levels for metals that were issued in March of 2016. The expanded list of 15 air toxics goes beyond metals and includes additional types of air toxics of potential short-term concern around the state, including naphthalene and hydrogen sulfide.”

Agency response to external scientific peer review –As part of the process for developing these updated SGCs, OHA and DEQ sought feedback from external peer reviewers with expertise in toxicology. This document was OHA’s and DEQ’s response to peer reviewer comments. We are not seeking comment on this document but hope it will provide some context for the proposal document.

Peer review comments –These are the comments OHA and DEQ received from external peer reviewers exactly as they were received. Note that these comments reflect the views of the peer reviewers themselves and not necessarily OHA, DEQ, or the agencies to which these reviewers belong.

SGC document submitted to peer reviewers– This the original draft of the SGC proposal document created by DEQ and OHA staff and submitted to external peer reviewers for their review and comments on October 3, 2016. This is the document that peer reviewers were responding to in their comments.

Air monitoring data related to Bullseye glass and other Portland area air toxics sites and provisional 24-hou screening levels used for comparison have been reported in the units nanograms per cubic meter (ng/m3). These are the units that required the least use of decimal places (e.g., 0.00X) in expressing the range of air toxics concentrations measured at Bullseye and other Portland area sites. In order to be consistent with the units used to express Oregon’s Ambient Benchmark Concentrations (ABCs) and the units used by other agencies to express health-based comparison values for air toxics, the SGCs in this proposal document are expressed in micrograms per cubic meter (µg/m3). Modifying the units used to express an air concentration does not change the actual concentration at all, just the number of decimal places needed to express the concentration. There are 1,000 ng/min 1 µg/m3. As an example, the proposed SGC for hexavalent chromium (chromic acid aerosol mist) is 0.005 µg/m3, which is exactly the same number as 5 ng/m3. In order not to confuse the reader, OHA and DEQ used the same units to express the SGCs for all air toxics in this document. However, the units selected (µg/m3) are different than the ng/m3 OHA and DEQ have been using to express air toxics monitoring data in the Portland metro area and wanted to alert readers to that change.