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Air Toxics: EPA Updates Several Regulations

  • 4/30/2020 9:21:00 AM
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EPA recently updated several federal regulations for hazardous air pollutants (also known as HAP or air toxics). EPA’s actions address the Risk and Technology Review (RTR) required under the U.S. Clean Air Act. In the following weeks, the Iowa Department of Natural Resource (DNR) will be providing additional information about the changes to the specific regulations (also known as National Emission Standards for Hazardous Air Pollutants or NESHAP).

Background (taken, in part, from Controlling Hazardous Air Pollutants)

The Clean Air Act requires EPA to address air toxic emissions from large industrial facilities in two phases.

The first phase is “technology‑based,” where EPA develops standards for controlling the emissions of air toxics from sources in an industry group or “source category” (for example, industrial boilers). These maximum achievable control technology (MACT) standards are based on emissions levels that controlled and low‑emitting sources in an industry are already achieving. Typically, MACT affects only a “major source” of air toxics (a source with a potential to emit at least 10 tons per year of any one HAP or 25 tons per year of any combination of HAPs).

The second phase is a “risk-based” approach called residual risk. In this step, EPA must determine whether more health-protective standards are necessary. Within eight years of setting the MACT standards, the Clean Air Act requires EPA to assess the remaining health risks from each source category to determine whether the MACT standards protect public health with an ample margin of safety, and protect against adverse environmental effects. On this same schedule, the Clean Air Act also requires EPA to review the standards and, if necessary, revise them to account for improvements in air pollution controls or prevention. The combined review of public health risk and air pollution control is called the “risk and technology review” (RTR).

Impact of the Recent Updates

For most of the recent NESHAP RTR updates, EPA has determined that the risks from emissions from affected source categories are acceptable and that there are no new cost-effective controls available. However, the updates do include revisions to the requirements for periods of startup, shutdown and malfunction and require electronic reporting of performance test results and compliance reports.

In some cases, EPA made minor amendments to correct errors, clarify requirements and provide technical amendments. EPA also provided additional flexibilities in a few of the final NESHAP RTRs, such as alternative testing methods or reduced monitoring. Additionally, a number of the NESHAP RTR updates do not currently affect any facilities in Iowa. A few of the recent and upcoming NESHAP RTRs, though, do include more substantive requirements for pollution control and monitoring, primarily to control emissions of ethylene oxide.

Implementation in Iowa

DNR plans to begin rulemaking to incorporate the updated standards—which is needed for DNR to have authority to carry out the rules. Until DNR receives delegated authority, EPA will implement the NESHAP RTR changes. DNR is available to answer questions about the new rules and will work with EPA Region 7 to assist facilities.

The DNR will review the changes and contact facilities which have substantively different requirements in their permits from the updated NESHAP. However, an affected facility should carefully review the updated NESHAP to be aware of any new requirements and compliance dates. An affected facility must still comply with the NESHAP RTR requirements even if the requirements are not included in an Iowa air permit.

In the upcoming weeks, please keep an eye on your inbox for ongoing updates about individual source categories.

For questions, please contact Christine Paulson (email:; phone: 515-725-9510) or Michael Hermsen (email:; phone: 515-725-9577).