Toxicological Risk Assessment for Fragrances and Perfume Oils: What the Toxicologist Actually Assesses

Toxicological Risk Assessment is a phrase that sounds far more intimidating than the idea behind it. Every maker of a scented candle, a wax melt, a reed diffuser, a room spray or a cleaning product has the same legal duty: the product they place on the market must be safe. In Great Britain that duty comes from the General Product Safety Regulations 2005, in the EU from the General Product Safety Regulation, and where the product is a hazardous chemical mixture the CLP Regulation adds classification and labelling requirements. A TRA is simply how a maker proves, with science, that the duty has been met.

This guide explains what a TRA is in plain English, the three steps every TRA follows, which products need one and which need a CPSR instead, what a good report contains, who is qualified to write it, how long it takes and what it costs, and exactly what to send to get one started.

A TRA in one paragraph

A Toxicological Risk Assessment takes a product apart on paper. It lists every substance in it, including the dozens of constituents inside a single fragrance oil. For each substance it establishes the hazard: does it irritate skin, sensitise, harm aquatic life, cause damage if inhaled or swallowed, and at what dose. It then works out exposure: how much of each substance a person actually takes in when they burn the candle in a normal room, handle the melt, or spray the room spray, including foreseeable misuse such as a child drinking from a diffuser. Finally it compares exposure against the level known to be safe, and states a conclusion: the product is safe as intended, or it is safe with specific restrictions and warnings, or it is not. That conclusion, with the reasoning and the assessor's signature, is the TRA.

The three steps every TRA follows

1. Hazard identification

The assessor establishes what each substance can do and the dose at which it does it, drawing on supplier Safety Data Sheets, published toxicology, regulatory opinions and the classifications already assigned under CLP. For fragrance materials this means sensitisation potential, phototoxicity for certain citrus and other natural constituents, and any restrictions. For carriers it might mean aspiration hazard or flammability. For a cleaning product it might mean corrosivity or eye damage. The output is a hazard profile for every substance, with the no observed adverse effect level or an equivalent threshold where one exists.

2. Exposure assessment

This is where a TRA becomes product specific. The same fragrance has completely different exposure in a candle, a diffuser and a body oil. The assessor models realistic use: for a candle, the fragrance released by evaporation and combustion into a room of typical size and ventilation over a typical burn; for a diffuser, continuous evaporation over weeks plus accidental contact or ingestion; for a spray, inhalation and contact with skin and eyes. The amount of product used, the frequency, the route into the body and the population using it, including children, all feed the calculation. The output is a systemic exposure dose for each relevant substance.

3. Risk characterisation

Hazard and exposure are brought together. This step, risk characterisation (risk characterization in US usage), is where the two earlier steps are converted into an actual conclusion. For substances with a safe threshold the assessor calculates a margin of safety, the ratio between the safe level and the estimated exposure, and expects a comfortable margin. For sensitisers the comparison is against accepted exposure limits for the product type, which is where IFRA category limits come in. For hazards with no safe threshold the approach is to eliminate or minimise. The result is the conclusion, plus the practical controls that follow from it: a maximum fragrance level, a required warning, a child resistant closure, a restriction on use, or a change of ingredient.

Which products need a TRA

The TRA is the assessment for consumer products that are not cosmetics. Cosmetics have their own mandatory format, the Cosmetic Product Safety Report, and a TRA cannot replace it. The dividing line is intended use: if the product is applied to the human body to clean, perfume, protect or condition it, it is a cosmetic and needs a CPSR; if it is not, it needs a TRA.

A full comparison is in our guide TRA vs CPSR: which safety assessment does your product need?.

TRA inside a cosmetic. Toxicologists also use the term for the assessment of a single ingredient, for example a novel botanical extract or an ingredient with limited published data, within a cosmetic. That ingredient TRA feeds into the CPSR as supporting evidence. It is a component of the cosmetic's safety case, not a substitute for the CPSR.

What a good TRA contains

• Product description and intended use. What it is, how it is used, by whom, and what foreseeable misuse looks like.
• Full composition. Every ingredient with its percentage, expanded to constituent level for fragrances and essential oils using the supplier documentation.
• Hazard profiles. The toxicological properties and thresholds for each substance of relevance, with sources.
• Exposure scenarios and calculations. The assumptions used and the resulting exposure estimates for each route.
• Risk characterisation. Margins of safety, comparison against limits, and the reasoning.
• CLP classification of the finished mixture. Derived from the same constituent data, with the resulting label elements.
• Conclusion and recommendations. Safe as intended or with conditions; maximum levels; warnings, instructions and packaging requirements such as child resistant closures.
• Assessor identity and signature. Name, qualifications and date, because the report is your evidence if anyone asks.

Who can write a TRA

Unlike the CPSR, where the law names the qualifications a signatory must hold, there is no statutory list for a TRA. That does not make it a job for anyone. Under general product safety law the maker must be able to show, if challenged by Trading Standards, a marketplace or a court, that the product was assessed competently. A TRA prepared by a qualified toxicologist or an experienced product safety assessor carries that weight; a document produced by a supplier's sales team or by software alone does not. Ask who will sign your report, what their qualifications are, and whether they will stand behind it.

Phoenix TRAs are prepared and signed by qualified toxicologists and safety assessors for fragranced and home fragrance products and for beauty adjacent and other consumer products, and our client verifications are available to review.

TRA, CLP and SDS: three outputs from one dataset

Makers often buy a TRA, then a CLP classification, then a Safety Data Sheet from three places, and end up with documents that disagree with each other. All three are derived from the same constituent list and concentrations. The TRA establishes the substances and their hazards; the classification applies CLP thresholds to those concentrations; the SDS presents the classification and handling information in the required sixteen section format. Commissioning them together costs less and, more importantly, produces a consistent set that will survive scrutiny.

Phoenix prepares the SDS for hazmat products in the EU and UK from the same assessment as the TRA.

A worked example of a margin of safety

Imagine a substance in a diffuser fragrance for which toxicology studies set a no observed adverse effect level of ten milligrams per kilogram of body weight per day. The exposure assessment estimates that an adult in a typical room is exposed by inhalation to 0.01 milligrams per kilogram per day when the diffuser is in continuous use. The margin of safety is ten divided by 0.01, which is one thousand. Assessors generally look for a margin of at least one hundred for systemic effects, to allow for differences between test animals and humans and between individual people, so this substance comfortably passes. Repeat that calculation for every substance of relevance, add the separate checks for sensitisation, phototoxicity and local irritation, and you have the core of the risk characterisation.

A TRA is not a Safety Data Sheet

The two are often confused because both are safety documents. A Safety Data Sheet is a standardised sixteen section communication document that tells professional users how to handle a hazardous mixture safely: its classification, first aid, fire fighting, storage and transport information. It does not assess whether the product is safe for consumers to use as intended; it assumes the product is what it is and describes its hazards. A TRA is the assessment that decides whether the product is safe in the hands of the people who will use it. An SDS is derived partly from the TRA's classification work, which is why the two should be prepared together, but holding an SDS is not evidence that a product has been risk assessed.

When a TRA needs updating

• A new fragrance or essential oil. Different constituents, different classification, new assessment.
• A change of supplier for the same fragrance name. Two suppliers' versions of the same scent can differ materially in composition.
• A change in fragrance percentage. Moving from six to eight percent can cross classification thresholds.
• A new format. Turning a candle fragrance into a wax melt or diffuser changes the exposure entirely.
• A regulatory change. New restrictions or reclassifications of constituents, which happen regularly, can change the conclusion.
• A complaint or adverse report. New real world evidence should prompt a review.

How long it takes and what it costs

A TRA is typically quicker and less expensive than a CPSR because there is no Product Information File, notification or Responsible Person chain to build around it. The time is driven almost entirely by the quality of your supplier documents. A candle range with complete IFRA certificates, allergen statements and SDS for every fragrance can be assessed in days; a range where the fragrance supplier will not disclose constituents can stall indefinitely. Many assessors price by product and offer range pricing for a set of fragrances in the same base, since the base and the exposure model are shared.

What to send to get started

• Formulation. Every ingredient and its percentage by weight in the finished product.
• Fragrance documents. SDS, IFRA certificate for the correct product category, and allergen statement or constituent breakdown for each fragrance or essential oil.
• Other raw materials. SDS or technical data sheet for waxes, carriers, bases, dyes and additives.
• Packaging. Container, closure, whether it is child resistant, label space and any outer box.
• Use and market. How the product is used, where it is sold, and whether you sell into the EU as well as Great Britain.
• A photo or sample. It answers more questions than a description.

If you are unsure whether you need a TRA, a CPSR or something else entirely, an expert regulatory consultation will settle it before you spend on the wrong report, and our allergen review can decode a fragrance's allergen content when the supplier paperwork is thin.

Related reading on the Phoenix blog

• TRA vs CPSR: which safety assessment does your product need?
• CPSR for body mist
• CPSR for whipped soap
• All regulatory compliance articles

Phoenix services mentioned in this article

• Toxicological Risk Assessment for fragranced products
• Toxicological Risk Assessment for beauty and personal care products
• Safety Data Sheets for hazmat products, EU and UK
• Allergen compliance review
• Expert regulatory consultation
• Contact Phoenix

Official sources and legislation

• General Product Safety Regulations 2005
• Regulation (EU) 2023/988, the General Product Safety Regulation
• CLP Regulation (EC) No 1272/2008 on classification, labelling and packaging
• HSE guidance on chemical classification and labelling
• Office for Product Safety and Standards
• Regulation (EC) No 1223/2009 on cosmetic products

About the author

Disclaimer: This article is general information, not legal advice. Regulations change and product decisions depend on your exact formulation, claims and market. Have your product assessed by a qualified professional before sale.