Extracted from Law360
Effective Oct. 1, California's Department of Toxic Substances Control is adding microplastics to its candidate chemicals list under the state's Safer Consumer Product regulations.
The regulation defines microplastics as plastics less than 5 millimeters in their longest dimension, whether intentionally manufactured at that size or generated through fragmentation of larger plastics. The listing's immediate message is measured, but consequential.
This is not a product restriction, but an expansion of the DTSC's future regulatory reach. It enables the agency to assess product-chemical combinations involving microplastics as potential priority products — the SCP program's point of regulatory leverage.
Companies whose products intentionally contain microplastics, shed plastic particles during ordinary use or release them at end of life should therefore treat the rule as an early warning — and an opportunity to shape the next phase of the DTSC's work.
The Green Chemistry Framework: A Staged Regulatory System
California's Green Chemistry law directs the DTSC to establish a process for identifying and prioritizing chemicals or chemical ingredients in consumer products that may be chemicals of concern. The implementing SCP regulations create a staged system, not a single, across-the-board ban.
The SCP process begins with identifying candidate chemicals, substances exhibiting hazardous traits or appearing on authoritative hazard lists in SCP regulations. The DTSC may then evaluate product-chemical combinations and propose them as priority products.
Manufacturers, importers, assemblers and retailers must notify the DTSC if their product has been listed as a priority product. Priority product manufacturers or other entities must perform an alternatives analysis, evaluating potential safer substitutes.
Based on that analysis, the DTSC may impose regulatory responses such as product reformulation, labeling requirements, use restrictions or sales prohibitions.
A substance becomes a candidate chemical through an incorporated authoritative list or the DTSC's independent hazard evaluation. The agency may then evaluate products containing that chemical.
Only a separate priority product rulemaking can trigger notification, alternatives analysis or regulatory response obligations. Candidate chemical listings are therefore screening tools, with priority product listings focused on compliance duties on a defined product-chemical combination.
What the Microplastics Listing Does
The candidate chemical listing does not prohibit microplastics, require companies to test products, trigger a priority product notification, require an alternatives analysis or establish product-specific limits.
The DTSC emphasized that the rule creates no current requirements for manufacturers or other businesses, concluding that the listing itself has no foreseeable impact because it does not name any priority products. The agency also states that product-specific economic impacts will be evaluated if it proposes a future priority product rulemaking.
But the listing does something material: It makes microplastics eligible to serve as the chemical of concern in a future SCP priority product action through its broad definition of microplastics. It covers both primary microplastics intentionally added to a product and secondary microplastics created as larger plastic articles fragment.
The definition does not include a lower size threshold, so the DTSC regards particles below 1 micron — nanoplastics — as within scope. It also contains no categorical exemptions for biodegradable, water-soluble, naturally derived or other specified polymers.
This scope gives the DTSC flexibility to study product formulation-based categories, as well as potential particle release during manufacture, consumer use, laundering, abrasion, weathering, disposal and other lifecycle stages.
This differs from a conventional ingredient-focused inquiry, and creates particular evidentiary and supply-chain challenges for companies that make durable goods, fabrics, coatings, packaging, tires, cleaning products, personal care products or components that can wear or fragment.
Why the DTSC Acted
The DTSC's technical rationale rests on three alleged hazard traits: environmental persistence, mobility in environmental media, and particle size or fiber dimension.
The agency relied on evidence it claimed demonstrated that microplastics occur in household dust, indoor air, drinking water, consumer products, stormwater, wastewater and ecosystems, and that people and wildlife may be exposed through ingestion, inhalation and dermal contact.
Stakeholder Concerns Presage the Next Rulemaking
The comments during the rulemaking process identify the factual and legal disputes likely to recur if the DTSC proposes a product-specific priority product rule. The most consequential objections fell into three related groups.
Breadth and Administrability of the Definition
Industry commenters asked the DTSC to establish a lower particle-size boundary, align with the European Union's definition and exclusions, and carve out biodegradable or water-soluble materials, natural polymers and materials that do not persist or behave like conventional plastic particles.
They argued that a definition without a lower threshold creates measurement and enforceability problems, and may capture materials that pose materially different environmental profiles.
The DTSC declined to add a lower bound or categorical exemptions, reasoning that no lower size eliminates the alleged hazard traits, and that exclusions would be premature before the agency considers a particular product and exposure scenario.
The practical implication is that future commenters will need product-specific evidence — not general assertions — to show why a material, particle range or use should fall outside a proposed rule.
DTSC Authority to Reach Secondary Microplastics
Commenters argued that the SCP program was designed around chemicals intentionally added to products, whereas secondary microplastics arise later from abrasion, degradation or fragmentation.
That distinction matters because release rates may turn on consumer behavior, product age, operating conditions, disposal and other variables not readily controlled or measured at the point of sale.
The DTSC responded that neither its statutes nor the existing framework limits it to intentionally added chemicals, and that the primary-versus-secondary distinction does not govern inclusion on the candidate chemicals list.
The agency's position preserves future regulatory options, but it also sets up a likely dispute over causal attribution, practicable mitigation and the fit between a product-specific obligation and lifecycle particle generation.
Feasibility and Economic Concerns
Commenters warned that notifications and alternatives analyses could be unworkable for products that generate secondary microplastics, that suitable substitutes may be unavailable or compromise safety and performance, and that broad product rules could increase consumer costs, reduce product choice or disrupt existing sustainability efforts.
The DTSC did not resolve those concerns at this threshold stage. It stated that a future product rule would consider exposure and significant or widespread adverse impacts, and would be subject to its own notice-and-comment process.
Why a Microplastics Priority Product Proposal Would Change the Stakes
A future priority product rulemaking would be a distinct regulatory event — not a foregone conclusion. The DTSC would need to identify a particular product-microplastics combination and support its proposal under the SCP prioritization criteria, including potential exposures and significant or widespread adverse impacts.
It would proceed through formal rulemaking with public notice and an opportunity for comment. That process should create a strong record for affected companies to address product function, exposure pathways, analytical capability, release rates, alternatives, economic effects and interactions with other regulatory programs.
If the DTSC ultimately designates a product as a priority product, the practical consequences can be substantial. The responsible entity may need to notify the DTSC and conduct an alternatives analysis.
That analysis is more than a search for a substitute material. It is a structured comparison of potential alternatives and their impacts.
The resulting regulatory response can range from no further action or information requirements to labeling, use restrictions, end-of-life requirements, product reformulation or sales restrictions. The outcome will depend on the specific product and record — not simply the fact that microplastics are now candidate chemicals.
The current agency research signals where attention may first fall.
The DTSC reports that it began by considering synthetic textiles, motor vehicle parts, beauty and personal care products, children's toys, artificial turf, building materials, and cleaning products, before narrowing its research to seven categories based on data availability, subject matter expert input and feasibility of SCP intervention.
That is neither a list of regulated products nor a definitive priority product short list. It is, however, a useful indicator of where companies should expect technical questions and information requests.
A Corporate Defense Playbook
The appropriate response is not immediate reformulation based solely on the candidate chemical listing. Premature changes can introduce product quality, safety, cost and sustainability risks. A more defensible approach is disciplined preparation.
Build a product and materials map.
Identify California products that intentionally contain small plastic particles or may release particles or fibers through use or disposal, including contract-manufactured products and sourced components.
Document product function and lifecycle performance.
For each material identified, preserve the reason it is used and the consequences of changing it. Relevant records may include product specifications, engineering and safety requirements, durability and wear testing, consumer use conditions, quality control standards, and release-control features.
Companies should also record existing mitigation, including design changes, maintenance instructions or manufacturing controls.
This evidence can help demonstrate that a product's actual release profile, safety function or feasible design constraints differ from assumptions that may be made in a broad product category assessment. These facts may be central to a future exposure or alternatives analysis.
Engage suppliers.
Obtain available information on polymer composition, additives, particle size, solubility, biodegradation claims, testing methods and material changes. Review contractual rights to obtain that information.
Where data are incomplete, identify the gap now and establish a protocol for supplier follow-up rather than waiting for a regulatory information request.
Evaluate data quality.
Do not rely on a single test result or a marketing claim. Determine what the test measures, its detection and reporting limits, the particle-size range it captures, whether it distinguishes plastic from other materials, and whether the tested conditions reflect real-world use and release pathways.
Companies should also assess sampling design, laboratory methods, reproducibility and comparability across suppliers and products.
Because the DTSC's definition has no lower size limit, companies should be able to explain what their methods can and cannot detect — and avoid overstating conclusions from tests that do not capture the full range of potentially relevant particles.
Assess alternatives realistically.
Evaluate — and preserve evidence concerning:
- Whether an alternative can meet the product's performance, durability, safety, hygiene, regulatory and consumer use requirements;
- Whether it creates different concerns across its lifecycle;
- Whether it can be manufactured at scale with reliable specifications and supply; and
- Whether it changes cost, product life, waste, recyclability or end-of-life outcomes.
A substitute that reduces particle shedding but materially compromises product safety, service life or another objective may not be a safer alternative in the SCP sense.
Companies should be prepared to substantiate those tradeoffs with product testing, supplier information, lifecycle data, and cost or feasibility analyses rather than general sustainability claims.
Monitor and participate early.
The DTSC is seeking release, exposure, impact and mitigation information. Supported comments and workshop participation can help distinguish among products and uses before a proposed priority product is selected.
The Bottom Line
Candidate today does not mean prohibited tomorrow — but it puts microplastics on the DTSC's regulatory runway.
The listing imposes no immediate SCP duties, and does not itself pronounce any product unlawful or unsafe. Still, it enables the DTSC to move beyond chemicals intentionally present in a formulation, and investigate products that may generate plastic particles over their life cycle.
For companies, the winning posture is neither complacency nor panic. Maintain accurate product intelligence, protect and develop the technical record, scrutinize alternatives realistically, and participate before future product-specific rules harden.