Key Takeaways:

• Effective October 1, 2025, California’s OEHHA establishes No Significant Risk Levels (NSRLs) for airborne, unbound, respirable titanium dioxide (TiO₂) particles, impacting manufacturers and users of TiO₂-containing products.
• RHP Risk Management helps clients understand product formulations against regulatory NSRLs and translates toxicology, exposure science, and regulatory strategy into actionable plans.
• Consumer product manufacturers should inventory products with TiO₂, assess exposure, benchmark against NSRLs, consider mitigation, and implement ongoing validation and monitoring to comply with Prop 65.

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Effective October 1, 2025, the California Office of Environmental Health Hazard Assessment (OEHHA)’s No Significant Risk Levels (NSRLs) under Proposition 65 for airborne, unbound, respirable titanium dioxide (TiO₂) particles take effect. The thresholds are:

• 440 µg/day for particles with diameters ≤ 10 µm
• 44 µg/day for particles with diameters ≤ 0.8 µm

This rulemaking is a key regulatory milestone for manufacturers, formulators, and downstream users of materials or products containing nano- or fine-particulate titanium dioxide.

Background: OEHHA, Proposition 65, and the Role of NSRLs

OEHHA is the California body charged with implementing Proposition 65 (the Safe Drinking Water and Toxic Enforcement Act of 1986). Under Prop 65, the state compiles lists of chemicals known to cause cancer or reproductive toxicity, and businesses must provide warnings or otherwise ensure exposures remain below safe levels. OEHHA also develops numeric thresholds such as NSRLs, which represent daily exposure levels below which the risk of cancer is deemed “not significant.”

For regulated chemicals, NSRLs help companies make defensible decisions about labeling, warnings, product reformulation, and risk assessments. They also provide clarity to regulators, downstream users, and consumers on acceptable exposure margins.

Understanding the Concern

Titanium dioxide (TiO₂) is ubiquitous in modern products: it’s used as a pigment, opacifier, UV filter, in paints/coatings, plastics, paper, cosmetics, and more. Bound or large particles are generally considered safe in many contexts. The concern arises when TiO₂ exists as airborne, unbound respirable particles that can be inhaled, penetrate deep into lung tissue, or deposit in alveolar regions.

Over time, inhalation of fine TiO₂ particles has been associated in animal studies with lung inflammation, fibrosis, and tumor formation under high exposure regimes. The new OEHHA NSRLs bring an explicit threshold for acceptable exposure from inhalation of these particles in consumer or occupational settings, thereby creating a new compliance consideration for relevant industries.

How RHP Helps Bridge Science, Safety & Compliance

RHP Risk Management partners with clients to help them better understand their product formulations against regulatory NSRLs and translate toxicology, exposure science, and regulatory strategy into actionable plans.

Expertise in Consumer Product Inhalation Safety

RHP Risk Management is actively engaged in advanced, real-world inhalation exposure research for consumer products containing mineral actives such as TiO₂ and ZnO.

Notably, RHP’s own Jacob Persky, MPH, CIH, recently presented on this topic at two scientific conferences (ISES 2025 and PSX 2025). At these conferences he presented, “Hazard Minimization vs. Risk Assessment: Approaches to Assessing Product Safety for Mineral Actives in Powder Sunscreens”, which described the work RHP’s Human Health Risk Sciences team conducted to evaluate several commercial powder sunscreens containing mineral actives (including TiO₂), using a controlled clean-room environment and real-time air monitoring. RHP scientists measured inhalation exposures under realistic usage scenarios and compared two approaches:

• The hazard minimization approach, which flags all particles under a cutoff (e.g. <10 µm) as potentially hazardous (as is done under some regulatory guidelines).
• Versus a risk assessment approach, which more deeply considers actual exposure, particle behavior (agglomeration/coating), and toxicological thresholds.

RHP’s study is an example of applying data-driven, defensible science toward consumer product inhalation safety, particularly relevant now as TiO₂ inhalation becomes a regulatory focal point.

Toxicology, Exposure Modeling & Risk Assessment

Our toxicology and exposure services are tailored to help clients interpret thresholds like the OEHHA NSRLs, integrate them into product stewardship programs, and conduct defensible assessments. We help with:

• Dose–response modeling and margin of safety calculations
• Lung dosimetry and deposition modeling
• Exposure reconstruction and simulation
• Uncertainty analysis and Bayesian/statistical method

These capabilities allow us to support both regulatory compliance and risk management decisions.

New Product Development & Compliance Strategy

When developing or reformulating consumer products (especially those with powders or aerosols), our team helps embed safety and compliance from the ground up. This includes selection of materials, assessing inhalation potential, screening alternative actives or coatings, and aligning with regulatory thresholds (e.g. for TiO₂).

Exposure Simulation Laboratory (ESL)

RHP’s team utilizes our state-of-the-art Exposure Simulation Laboratory to recreate realistic use scenarios in controlled settings, measure emissions and exposures, and generate critical empirical data to feed into exposure models.

Consumer Safety & Stewardship

RHP understands product/user interactions, and helps clients in develop labeling, mitigation strategies, and safety communication consistent with regulatory mandates.

PFAS & Broader Chemical Expertise

RHP scientists also have deep experience across emerging contaminants such as per- and polyfluoroalkyl substances (PFAS). This breadth enables us to serve clients working across multiple chemical domains.

What Can Consumer Product Manufacturers Do To Stay In Compliance With Prop 65?

With OEHHA’s TiO₂ NSRLs coming into effect in 2026, here are steps clients should consider:

1. Inventory & screening — Identify products, processes, or intermediates that may generate respirable TiO₂ dust or emissions.
2. Exposure assessment & modeling — Use lab simulation or monitoring data combined with deposition modeling to estimate inhaled dose.
3. Benchmark against NSRLs — Compare estimated doses to the 440 µg and 44 µg thresholds to assess margin of safety or need for warning.
4. Mitigation & design changes — Consider reformulation, altering particle size distributions/coatings, or engineering controls to reduce inhalable emissions.
5. Risk communication & compliance — Decide whether warning labels, documentation, or risk management steps are needed.
6. Ongoing validation & monitoring — Use empirical data (e.g. exposure simulation testing) to confirm that exposures are adequately controlled within Safe Harbor levels.

Contact RHP Risk Management to Help Stay In Compliance With Prop 65

RHP Risk Management is an environmental and occupational health consulting firm of scientists, toxicologists, public health professionals, and risk assessors that cover practices including environmental engineering, industrial hygiene, exposure science, and human health interaction and risk assessment.

RHP works with clients to develop solutions to their most pressing concerns. Understanding exposures and risks through a grounding in a sound, defensible, state-of-the-art scientific approach gives our clients peace of mind. Empowered by a comprehensive understanding of exposure we can provide, clients with reliable, strong data and tools to recognize unseen business and liability risks, manage known risks and mitigate, target areas for control systems, comply with regulations, and be better braced for regulatory or liability actions.