CFR›Title 40›Chapter I›Part 421›Subject Group General Provisions ContainsSections 421.1–421.5CorpusDaily eCFRDisplayed edition2026-09-17Last updated2026-09-17 Sections 421.1 § 421.1 Applicability. 421.2 § 421.2 [Reserved] 421.3 § 421.3 Monitoring and reporting requirements. 421.4 § 421.4 Compliance date for pretreatment standards for existing sources (PSES). 421.5 § 421.5 Removal allowances for pretreatment standards. Previous G Subpart G—Primary Lead Subcategory Next H Subpart H—Primary Zinc Subcategory