Chemical Substitution Programs and the Hierarchy of Controls
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Chemical Substitution Programs and the Hierarchy of Controls

Build a defensible chemical substitution program — hierarchy of controls, TSCA Section 6, OSHA General Duty Clause, and a documented alternatives assessment.

by iSi Environmental

The hierarchy of controls is on the wall in almost every plant we walk into. Five tiers, drawn as a pyramid: elimination, substitution, engineering controls, administrative controls, PPE. NIOSH formalized it. OSHA cites it. Every safety training deck mentions it (NIOSH, Hierarchy of Controls; OSHA, Recommended Practices for Safety and Health Programs — Hazard Prevention and Control).

And in the same plants, the actual response to a chemical hazard almost always lands at tier three or below. We add a fume hood. We extend the LEV duct. We move people upwind. We write a respiratory protection program and fit-test the crew. We run training. We do tier three through tier five well.

What we rarely see is a documented chemical substitution program — the operational machinery that makes tier two of the hierarchy real. Substitution comes second only to elimination in effectiveness, but it requires program infrastructure that most plants have never built. In 2026, that gap is no longer a stewardship issue. It is a compliance issue, and EPA is writing the deadlines.

This is a working methodology for an EHS lead who is consolidating a chemical inventory and trying to land at a substitution program that an OSHA inspector or an EPA TSCA auditor will recognize as defensible.

Why “Hierarchy of Controls” Is Meaningless Without a Substitution Roadmap

The pyramid does not implement itself. NIOSH ranks substitution as the second-most-effective control because removing a hazardous chemical from the workplace eliminates the exposure rather than managing it. The agency is explicit that substitution “involves replacing something that produces a hazard with something that does not produce a hazard or produces a lesser hazard” (NIOSH, Hierarchy of Controls).

That definition is operational. It demands that someone has compared the hazards of two chemicals, decided which is lower, validated that the new one performs the function, and put the change into the production line. None of that happens by accident. It happens through a written program with five stages — inventory, function statement, alternatives assessment, pilot, documentation — or it does not happen at all.

The plants where it does not happen end up with a hierarchy of controls that effectively starts at tier three. Engineering controls become the default tool because they can be specified, purchased, and installed without ever asking the harder question: should this chemical be in the building in the first place?

That question is now being asked, with deadlines attached, by EPA.

The TSCA Section 6 Forced-Substitution Wave

The Toxic Substances Control Act gives EPA authority under Section 6(a) to issue risk-management rules for chemicals it has determined “present an unreasonable risk of injury to health or the environment” under Section 6(b)(4)(A) (15 U.S.C. 2605). Between 2024 and 2025, EPA finalized risk-management rules for six high-volume industrial chemicals, with phased compliance dates running through 2027:

  • Methylene chloride (MeCl, DCM). Final rule April 30, 2024 (89 FR 39254). Most consumer uses prohibited. Commercial and industrial uses subject to a Workplace Chemical Protection Program (WCPP) with an EPA Existing Chemical Exposure Limit (ECEL) and phased implementation.
  • Trichloroethylene (TCE). Final rule December 17, 2024 (89 FR 102568). Most uses prohibited; remaining industrial uses require a WCPP with an ECEL of 0.2 ppm. Section 6(g) postponements and judicial review proceedings are active in 2026.
  • Perchloroethylene (perc, PCE). Final rule December 18, 2024 (89 FR 103560). Dry-cleaning machine prohibition phased; remaining industrial uses require a WCPP with an ECEL of 0.14 ppm.
  • Carbon tetrachloride. Final rule December 18, 2024 (89 FR 103084). WCPP with an ECEL of 0.03 ppm.
  • 1-Bromopropane (1-BP). Final rule August 8, 2024 (89 FR 64754). Use prohibitions and WCPP requirements phased 2025–2027.
  • 1,4-Dioxane. Final rule November 26, 2024 (89 FR 93724). Worker protection requirements and conditions-of-use restrictions.

EDC (1,2-dichloroethane) is next in line. EPA finalized its risk evaluation on May 5, 2026; the Section 6(a) risk-management rule is expected late 2026 or 2027 (EPA, TSCA Section 6 Risk Management for Existing Chemicals).

What these rules have in common is that they impose a federal compliance deadline on a process change. A facility that uses methylene chloride in adhesion testing, vapor degreasing, or paint stripping is not deciding whether to consider an alternative. It is being told, by a date certain, to either (a) implement an EPA-prescribed WCPP with monitoring, regulated areas, respiratory protection, and recordkeeping, or (b) substitute the chemical out of the process.

Option (b) is the one with a meaningful operational outcome. Option (a) is a permanent administrative load.

The plants that built substitution programs before the final rule had years to evaluate alternatives, run pilots, and validate performance. The plants that did not are running emergency replacement projects against EPA deadlines, with the cost premium that comes with rushed material qualification.

OSHA’s General Duty Clause and Substitution as “Feasible Means”

The other regulator to watch is OSHA. Section 5(a)(1) of the OSH Act — the General Duty Clause — requires every employer to furnish a workplace “free from recognized hazards that are causing or are likely to cause death or serious physical harm” (29 U.S.C. 654; OSHA, Section 5: Duties).

For a General Duty Clause citation to stand, OSHA must establish four elements: a recognized hazard, a serious or fatal potential outcome, a feasible means of abatement, and the employer’s failure to implement that means (OSHA Field Operations Manual CPL 02-00-164). The third element — feasible means of abatement — is where substitution enters.

When a less hazardous chemical is commercially available and technically capable of performing the function, OSHA can cite a facility for not implementing it. We have seen this play out with hexavalent chromium plating substitutes, methylene chloride paint-stripper substitutes, and 1-BP solvent substitutes long before EPA’s risk-management rules took effect. The General Duty Clause has been the back-channel substitution lever for years.

Maximum penalties under the January 2026 inflation adjustment: serious or other-than-serious violations at $16,550 per instance; willful or repeated violations at up to $165,514 per instance (29 CFR 1903.15; OSHA, OSHA Penalties).

The defensibility question, when an OSHA inspector asks why the plant continued to use a chemical when a safer alternative existed, is a documentation question. The plant that has a written alternatives assessment showing why each candidate alternative failed on technical performance, supply availability, or cost-feasibility grounds is in a defensible position. The plant that has no record of having looked is not.

That brings us to the methodology.

A Five-Stage Substitution Program Methodology

What follows is the workflow we use when we build or rebuild a substitution program. It is structured to produce a written record an OSHA inspector or an EPA auditor will recognize.

Stage 1 — Inventory and Hazard Scoring

Build a current chemical inventory that captures every product, blend, and process chemical on site. For each line item, record:

  • Chemical name, CAS number, manufacturer, current SDS revision date
  • Quantity on site, storage location, departments and processes that use it
  • GHS health hazard classifications from the SDS (acute toxicity, carcinogenicity, reproductive toxicity, STOT-SE, STOT-RE, sensitization)
  • Federal regulatory flags: OSHA substance-specific standard status (lead, hex chrome, beryllium, silica, methylene chloride, 1-BP, etc.), TSCA Section 6 risk-management status, TSCA SNUR listing under 40 CFR Part 721, EPA Safer Choice / SCIL listing, ATSDR Substance Priority List ranking
  • State regulatory flags: California Proposition 65, Massachusetts TURA, Washington Children’s Safe Products Act, Maine PFAS reporting, and others as applicable

Then assign a hazard band. NIOSH’s Occupational Exposure Banding process (NIOSH 2019-132 and the OEB e-Tool) takes GHS hazard classifications as input and outputs Bands A through E, with A being the most hazardous (NIOSH, Occupational Exposure Banding). Tier 1 banding is fast — typically two to five minutes per chemical — and is a defensible starting point when no OSHA PEL exists.

Anything in Band A or B is a substitution candidate by hazard alone. Anything on the active TSCA Section 6 list is a substitution candidate with a federal compliance date attached.

Stage 2 — Function-Based Substitution

The single most common reason substitution programs stall is that they ask the wrong question. They ask, “What can replace methylene chloride?” The right question is, “What is methylene chloride doing in our process, and is there a different way to accomplish that function?”

Function-based substitution forces past the inventory bias of “we use solvent X because we always have.” It opens three categories of solution that the chemical-name framing closes off:

  1. Drop-in chemical substitute. A different chemical that performs the same function in the same equipment. Replace methylene chloride paint stripper with a benzyl alcohol or DMSO-based formulation. Replace 1-BP vapor degreasing with a hydrocarbon/oxygenated solvent blend. Drop-in candidates are the fastest to qualify because they touch the smallest number of process variables.
  2. Process substitution. Change the process so the function is performed differently. Replace solvent vapor degreasing with aqueous ultrasonic cleaning. Replace solvent-based adhesion testing with mechanical pull-off testing. Process substitutions are slower to qualify because they require equipment changes, but they produce the largest hazard reduction.
  3. Material redesign. Change the upstream input so the chemical is no longer needed. Switch from a coating system that requires aggressive solvent stripping to a system that can be removed mechanically. Material redesign is the longest path to qualify, but on multi-decade product lines it produces a permanent removal.

Write the function statement in writing for every substitution candidate. The statement names what the chemical is doing — “removes cured polyurethane coating from masking fixtures,” not “the solvent we use in the masking line.” The function statement is what allows the alternatives assessment to evaluate apples-to-apples options across all three categories.

Stage 3 — Alternatives Assessment

This is the analytic core, and it is what auditors look for. Three public frameworks are recognized:

  • EPA Safer Choice / Design for the Environment (DfE) and the Safer Chemical Ingredients List (SCIL). EPA-curated list of functional chemical classes — surfactants, solvents, chelators, preservatives — where each ingredient has been screened against EPA’s Safer Choice criteria (EPA, Safer Chemical Ingredients List). Useful as a starting filter for cleaners, surfactants, and formulated products.
  • Interstate Chemicals Clearinghouse (IC2) Alternatives Assessment Guide v1.1. The state-government framework, used by Washington, Massachusetts, California, and others. Defines a tiered process: scoping, hazard assessment, performance evaluation, cost and availability, exposure assessment, life-cycle considerations, decision (IC2, Alternatives Assessment Guide v1.1).
  • GreenScreen for Safer Chemicals. Independent benchmark hazard assessment method maintained by Clean Production Action. Produces a 1–4 GreenScreen Benchmark score that can be cited as the hazard column in the alternatives matrix (Clean Production Action, GreenScreen for Safer Chemicals).

The alternatives assessment matrix evaluates each candidate across at least four dimensions:

  1. Technical performance. Will it do the function? Lab data and pilot data, not vendor claims.
  2. Health hazard. GHS classifications, NIOSH OEB band, GreenScreen benchmark, regulatory flags.
  3. Environmental hazard. Aquatic toxicity, persistence, bioaccumulation, VOC and HAP status, GHG profile, waste stream classification.
  4. Cost and operational fit. Per-unit cost, equipment compatibility, supply chain reliability, downstream waste disposal pathway.

The output is a scored matrix and a written decision memo. Even a conclusion of “no acceptable substitute is currently available” — properly documented — is a defensible position. An undocumented “we looked into it” is not.

This is also where EPA’s pollution prevention program (P2, established under the Pollution Prevention Act of 1990, 42 U.S.C. 13101) lives. Source reduction through substitution is the highest-tier P2 outcome, ahead of recycling, treatment, and disposal (EPA, Pollution Prevention).

Stage 4 — Pilot and Scale-Up

Substitution failures most often surface during scale-up, when a chemical that worked in lab conditions fails on the production floor. Build the pilot phase into the program rather than treating it as the last step of procurement.

  • Pilot the substitute in a controlled production area, in parallel with the existing chemical where possible.
  • Capture exposure data before and after, with personal sampling. The substitution justification needs measured data, not assumption. Pre- and post- comparisons are also what allow you to claim the hazard reduction in the documentation.
  • Capture process metrics: cycle time, defect rate, equipment wear, downstream waste characterization. A substitution that creates a new RCRA-listed waste stream is not a substitution improvement; it is a hazard transfer.
  • Run the pilot for a minimum of one full operating cycle, including any seasonal or shift-pattern variation.
  • Sign off the pilot in a memorandum from the industrial hygienist or environmental professional, with the data and the conclusion.

Then scale up across the affected processes, with monitoring continuing through the first full quarter of production use. SDSs, container labels, the HazCom training module under 29 CFR 1910.1200, and any process safety information for PSM-covered processes (29 CFR 1910.119) all update at scale-up.

Stage 5 — Documentation for OSHA and EPA Defensibility

The substitution program lives or dies in its written record. The substitution file for each chemical should contain:

  • The function statement (Stage 2)
  • The hazard scoring of the original chemical and each alternative considered (Stage 1, Stage 3)
  • The alternatives assessment matrix and the decision memo (Stage 3)
  • Pilot data and the final scale-up authorization (Stage 4)
  • Updated SDSs, container labels, HazCom training, and (where applicable) PSM process safety information
  • For TSCA Section 6 chemicals: the full WCPP record set — regulated area designation, exposure monitoring records, respiratory protection program documentation, and the recordkeeping required by the relevant Section 6 rule

The substitution file is what an OSHA inspector reads when they ask, “Why are you still using this chemical?” or “Why did you change to this chemical?” It is what an EPA inspector reads when they verify TSCA Section 6 compliance. It is what an attorney reads when defending a tort claim alleging that the employer used a chemical when a safer alternative existed.

If the file does not exist, the answer to all three questions is the same: we did not have a process.

A Note on TSCA Section 5 SNURs — Don’t Substitute Into a Pre-Market Trap

One closing trap worth flagging. EPA’s TSCA Section 5 Significant New Use Rules (SNURs), codified at 40 CFR Part 721, freeze the universe of allowable uses for hundreds of new chemicals reviewed under the Section 5 Premanufacture Notice (PMN) process (EPA, Significant New Use Rules). When a SNUR is in place, any change of use — including a substitution that brings a SNUR-listed chemical into a new application — triggers a Significant New Use Notice (SNUN) at least 90 days before the new use begins.

Substitution programs that pull from new-chemical lists need to check SNUR status for each candidate, or they end up with a Section 5 pre-market reporting violation on top of the Section 6 problem they were trying to solve.

How iSi Helps

A substitution program is an annual operating workflow, not a project. Inventories change as suppliers reformulate. TSCA Section 6 adds chemicals every cycle. The alternatives assessment for a chemical with no acceptable substitute today should be re-run when the market produces one tomorrow.

iSi’s industrial hygiene consulting practice runs substitution programs as a standing service — function statements, alternatives assessments, pilot design and monitoring, the WCPP build-out for facilities affected by TSCA Section 6 rules, and the full documentation package. For multi-site clients, we run the program through the EHS COOP retainer so the substitution file stays current across all locations on a single recurring engagement, rather than as a series of one-off projects each time EPA finalizes a new rule.

If you are looking at a TSCA Section 6 deadline, an OSHA recognized-hazard exposure, or a chemical inventory you want to consolidate before the next regulatory cycle catches up to it, that is the conversation. Call (316) 264-7050 to talk through where your program is and what stage you are missing.

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