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  2. Sulfur Dioxide (SO2) Pollution

Specific Elements for Each of the Major SIP Types for Sulfur Dioxide (SO2)

Infrastructure State Implementation Plan (SIP)

An infrastructure SIP, or i-SIP, is a requirement for all states, regardless of designation. Even areas in attainment must demonstrate what controls they will continue to use and regulate in order to remain in attainment.

Nonattainment New Source Review SIP

  • EPA's New Source Review (NSR) program requires major stationary sources of air pollution in nonattainment areas to get permits before construction starts:
    • Search the NSR Policy and Guidance Document Index (hint: use the Filter box at the top right of the index to search titles by keyword)
    • RACT/BACT/LAER Clearinghouse (RBLC): database of control technologies for achieving the lowest achievable emission rate (LAER)
  • Startup, shutdown, and malfunction (SSM) emissions

Nonattainment Area SIP

  • If an area is designated as nonattainment, the state must develop an additional SIP detailing the path to attainment. The SIP will require different elements depending on how far the area is from being able to reach attainment.
    • Nonattainment SIP requirements for SO2

Interstate transport SIP

  • Interstate Air Pollution Transport: upwind transport of pollutants across state borders makes it difficult for downwind states to meet health-based air quality standards for SO2.
    • Cross-State Air Pollution Rule (CSAPR) provides the regulatory basis for reducing interstate air pollution.

Redesignation SIP, or maintenance SIP

  • Redesignations and Clean Data Policies

Sulfur Dioxide (SO2) Pollution

  • Sulfur Dioxide Basics
  • Setting & Reviewing SO2 Standards
  • Primary SO2 Standard Regulatory Actions
  • Secondary NO2 and SO2 Standard Regulatory Actions
  • Implementing SO2 Standards
  • Primary SO2 Standard Implementation Actions
  • SIP Checklist Guide
  • SIP Training Presentations and Assistance
  • SO2 Measurement and SIP Data
  • Other Criteria Air Pollutants
Contact Us about Sulfur Dioxide (SO2) Pollution
Contact Us to ask a question, provide feedback, or report a problem.
Last updated on April 17, 2025
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