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Technology Transfer Network - OAR Policy and Guidance





  • On June 1, 2006, the Environmental Protection Agency (EPA) proposed amendments to the Clean Air Act standards that limit emissions of toxic air pollutants from synthetic organic chemical manufacturers. The proposed rule is posted at: https://www3.epa.gov/ttn/oarpg/t3pfpr.html
  • EPA issued the air toxic standard for synthetic organic chemical manufacturers, known as the Hazardous Organic National Emissions Standards for Hazardous Air Pollutants (HON), in 1994. This rule is one of 96 rules called maximum achievable control technology (MACT) standards that require 174 industry sectors to eliminate 1.7 million tons of 187 toxic air pollutants. Congress listed these toxic air pollutants in the Clean Air Act.
  • The HON standards reduce air toxic emissions by approximately 440,000 tons per year from process vents, storage tanks, equipment leaks, wastewater systems, and transfer racks at large chemical manufacturers. This represents an approximately 90% reduction from emissions levels before the MACT requirements took effect.
  • EPA has identified 238 facilities covered by the HON.
  • The Clean Air Act now requires EPA to assess the risk remaining after application of the 1994 MACT standard. This is known as a residual risk assessment.
  • Also at this time, EPA must review and revise, as necessary, the 1994 standards by taking into account developments in practices, processes and control technologies.
  • The risk assessment found that after application of the 1994 standards, the chronic cancer, noncancer, and acute risks to humans, as well as ecological effects from these facilities are low enough to be judged acceptable. EPA policy considers risk acceptable if the risk to the most exposed individual is approximately 100 in a million or less.
  • EPA is proposing two options for amending the 1994 standards. These options are based on the risk assessment and also consider practices, processes and emission control technologies.
  • Make no revisions to the 1994 standards on the basis that the current level of risk is acceptable.
  • Require additional controls to provide additional risk reduction to exposed individuals. This option would reduce the cancer risk for approximately 450,000 exposed individuals at a capital cost of $14 million and annualized cost of $13 million.
  • Today’s action announces EPA’s co-proposal and requests public comments on the proposed amendments, residual risk assessment and technology review.
  • A 60-day comment period will begin at the date of publication of the proposal in the Federal Register.

  • The Clean Air Act requires EPA to regulate toxic air pollutants, also known as air toxics, 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). These MACT standards are based on emissions levels that are already being achieved by the better-controlled and lower-emitting sources in an industry.
  • Within 8 years of setting the MACT standards, the Clean Air Act directs EPA to assess the remaining health risks from each source category to determine whether the MACT standards appropriately protect public health. This second phase is a “risk-based” approach called residual risk. Here, EPA must determine whether more health-protective standards are necessary.
  • Also, every 8 years after setting the MACT standards, the Clean Air Act requires that EPA review and revise the standards, if necessary, to account for improvements in air pollution controls and/or prevention.

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