Georden Jones, Founder, The Peer Review · Last updated: August 28, 2026
The Short Answer
For decades, most nail polish shared three core ingredients known in the industry as the “toxic trio”: toluene (the solvent that keeps polish spreadable), dibutyl phthalate or DBP (a plasticizer that stops the dried polish from chipping), and formaldehyde or a formaldehyde-releasing resin (a hardener). Most mainstream brands have reformulated away from this exact combination, but reformulating does not mean the replacement ingredients are automatically safer. The most common substitute for DBP, a chemical called triphenyl phosphate (TPHP), shows up in about half of polishes on shelves, and a Duke University and Environmental Working Group study found it absorbed into every single study participant’s body within hours of a single manicure [3]. The strongest evidence on this page is occupational: nail salon workers, who handle these chemicals daily in poorly ventilated rooms, show consistently elevated rates of respiratory and skin problems across a large 2025 review of the research [2][4]. The weakest link in the whole picture is trust in the label itself: peer-reviewed testing has repeatedly found “toluene-free” and “DBP-free” polishes that still contained meaningful amounts of the chemical they claimed to exclude [8].
Evidence Rating: Mixed Signals. The occupational health picture for nail salon workers is well established across a large body of exposure and health-outcome research, including a 2025 systematic review [2][4]. Dermal absorption of TPHP from a single manicure is also directly measured and confirmed in humans [3]. What is less settled is how much risk an occasional home user takes on from painting their own nails a few times a month, since most of the strongest health data comes from people exposed daily at much higher concentrations. Layered on top of the chemistry is a documented labeling problem: independent testing has repeatedly found “free-of” claims that do not match the bottle’s actual contents [8][9].
Table of Contents
- Identify: What Is in the Bottle
- Where These Chemicals Hide
- How They Affect You and Enter the Body
- Investigate: Three Concerns, Ranked by Evidence
- Do “Free” Labels Mean What They Claim?
- What Canada Regulates, and What It Does Not
- What Canada, the US, and the EU Require
- Inform: What This Means for You
- Improve: How to Reduce Exposure Without Giving Up Manicures
- What This Does Not Mean
- FAQ
- The Bottom Line
- References
Identify: What Is in the Bottle
Nail polish needs to do three jobs at once: spread evenly, stay flexible enough not to crack, and dry into a hard, glossy film. For decades, the standard way to hit all three was toluene as the solvent, dibutyl phthalate as the plasticizer, and formaldehyde or a formaldehyde-releasing resin (often toluenesulfonamide-formaldehyde resin) as the hardener, a combination the industry itself came to call the “toxic trio” [1][2].
Consumer pressure and some regulatory action pushed most major brands to drop this exact combination, and “3-free,” “5-free,” and similar labels emerged to signal the change. But a formula has to replace a dropped ingredient with something that does the same job, and the replacement for DBP in roughly half of polishes on shelves today is triphenyl phosphate, or TPHP, an organophosphate plasticizer [3][6]. TPHP was not a new, unstudied molecule when it entered nail polish. It had already been flagged as a chemical of concern in flame retardants and furniture foam, and animal studies link it to endocrine disruption [3][6]. Swapping DBP for TPHP addressed one specific criticism (this exact plasticizer, this exact carcinogenicity classification) without necessarily addressing the underlying question of whether nail polish needs a plasticizer with hormone-disrupting potential at all.
Where These Chemicals Hide
These are not confined to a single product type [1][2]:
- Standard nail lacquer. The original home of the toxic trio and its replacements, including most drugstore and salon polish brands.
- Nail hardeners. Formulated with a higher formaldehyde concentration than regular polish specifically to stiffen weak or splitting nails, and treated as a distinct product category under Canadian cosmetic regulation, covered below.
- Gel and shellac systems. Use a different chemistry (photoinitiators cured under UV or LED light) but often still include plasticizers like TPHP, and add a UV exposure consideration of their own.
- Acrylic and dip powder systems. Rely on different solvents and monomers, including methyl methacrylate, which the FDA has restricted but which nail salon air testing still detects because it persists in some nail products despite that restriction [2][4].
- Nail salon air. Because these are volatile or semi-volatile compounds, they do not stay in the bottle. They accumulate in the air of a poorly ventilated salon over the course of a workday, which is the exposure route behind the occupational data below.
How They Affect You and Enter the Body
The exposure route depends heavily on whether you are an occasional user or someone who handles these products for a living [2][3][4].
- Dermal absorption is the primary route for at-home use. A 2015 Duke University, Environmental Working Group, and Boston University study had participants paint their nails once, then tested their urine 10 to 14 hours later. Every one of the 26 participants showed a large increase in a TPHP breakdown product, and levels dropped significantly when participants wore gloves during application, which points to skin contact, not inhalation, as the main way TPHP gets into a home user’s body from a single manicure [3].
- Inhalation is the dominant route for salon workers. A 2025 pilot ventilation study in New York City nail salons and a broader 2025 systematic scoping review both found volatile organic compound concentrations exceeding occupational exposure limits in a majority of salons tested, alongside inadequate ventilation in the large majority of locations studied [2][4]. Workers breathe these compounds for a full shift, day after day, which is a fundamentally different exposure than a home user’s occasional inhalation while a bottle is open.
- Occupational skin contact compounds the dermal route. Salon technicians also have their hands in direct, repeated contact with these products, layering dermal absorption on top of inhalation in a way an occasional home user does not experience.
Investigate: Three Concerns, Ranked by Evidence
1. Occupational health effects in nail salon workers (strongest evidence). A 2025 systematic scoping review synthesizing 42 studies published between 2013 and 2024 found consistent evidence linking nail salon work to occupational asthma, chronic dermatitis, and other respiratory effects, with inadequate ventilation documented in 71% of salons assessed and VOC concentrations regularly exceeding occupational exposure limits [2][4]. This is the best-proven harm on this page, and it falls almost entirely on people who work in this environment daily, not on someone getting a manicure once a month.
2. The toxic trio’s individual toxicology (well-characterized hazards, exposure-dependent risk). Each of the three legacy ingredients has an independently well-documented hazard profile: toluene is linked to central nervous system, reproductive, and respiratory effects at sufficient exposure; formaldehyde is a recognized human carcinogen and respiratory irritant; and DBP is classified as a reproductive and developmental toxicant that acts as an endocrine disruptor [1]. What is less clear is how much of that hazard translates into realized risk for someone using a reformulated, “trio-free” polish only occasionally, since hazard (what a chemical can do at some dose) and risk (what it does at your dose) are not the same question. See Hazard vs. Risk for that distinction applied directly.
3. The TPHP substitution (real absorption confirmed, long-term outcome data still thin). The 2015 Duke/EWG/Boston University study confirmed that a single manicure with a TPHP-containing polish measurably raises the body’s TPHP metabolite levels within hours, and TPHP is an endocrine disruptor in animal studies [3]. What has not yet been established is what repeated, years-long exposure at typical consumer-use frequency does to long-term health outcomes in humans. The absorption is proven; the downstream health consequence at consumer-level exposure is still an open research question.
Do “Free” Labels Mean What They Claim?
This is where the evidence gets uncomfortable in a different way, because it is not really a toxicology question at all. It is a question of whether the label on the bottle can be trusted, and the peer-reviewed testing on this specific point is not encouraging.
A 2018 study in Environmental Science & Technology tested a range of nail polishes marketed with “free-of” claims and found real, quantifiable mismatches between the label and the bottle: TPHP was detected in two of three polishes marketed as TPHP-free, and the researchers documented at least six different working definitions of what brands mean by “10-free,” with no standard governing the term [8]. Earlier testing by California’s environmental regulator found similar gaps: among polishes marketed as “3-free,” one still contained DBP at a concentration of 82,000 parts per million, and four contained toluene at up to 180,000 parts per million [8]. A 2023 laboratory study by California’s Department of Toxic Substances Control, testing a broad range of nail products sold in 2023, continued to find plasticizers and other chemicals of concern present in products that did not disclose them on the label [9].
The reason this keeps happening is structural, not just a matter of individual bad actors: no government body defines “10-free,” “13-free,” or any other “n-free” number, so any brand can apply the term to whatever set of chemicals it chooses to exclude, and nothing requires that claim to be verified before the product reaches a shelf [8]. A higher “free” number is also correlated with a real price premium, which is worth knowing when deciding whether that number is buying you a verified formulation change or just a marketing story.
What Canada Regulates, and What It Does Not
Health Canada’s Cosmetic Ingredient Hotlist treats these three legacy ingredients very differently from each other, and the differences matter [5].
Formaldehyde is restricted, with a specific carve-out for nail hardeners. In most cosmetic products, formaldehyde is capped at low concentrations (0.2% as a preservative in non-oral products, far lower in products that could release formaldehyde vapour), and it is not permitted in aerosols at all [5]. Nail hardeners get their own exception: a higher formaldehyde concentration is permitted specifically for this product category, on the condition that it is sold with nail shields and directions for use that limit contact with surrounding skin [5]. This is a case where Canada regulates the same chemical differently depending on exactly what job it is doing in the formula.
DBP is not restricted in Canadian cosmetics, unlike the EU. This is the most important gap on this page for a Canadian reader. The European Union bans DBP outright in cosmetics and personal care products. Canada does not. Health Canada restricts several phthalates, including DBP, in children’s toys and childcare articles, but that restriction does not extend to cosmetics, cleaning products, or other consumer goods [5][7]. In 2011, the Government of Canada published an assessment of phthalate concentrations and estimated dermal exposure from cosmetics and personal care products and concluded that overall exposure was low enough to be unlikely to pose a health risk to Canadian consumers [7]. That is a real government risk assessment, not a regulatory gap born of neglect, but it is also a conclusion reached in 2011, based on typical-use assumptions, not a standing prohibition the way the EU has one.
Toluene is restricted, with conditions attached to specific product types, though the exact concentration limits and required cautionary statements are set out directly in the Hotlist document itself rather than as a blanket number that applies the same way everywhere [5].
The pattern worth remembering: “restricted” on Health Canada’s list does not mean “banned,” and the same ingredient can carry different limits depending on which product category it appears in.
What Canada, the US, and the EU Require
| Requirement | Canada | United States | European Union |
|---|---|---|---|
| Formaldehyde in nail products | Restricted; higher concentration permitted specifically in nail hardeners with shields and use directions required [5] | No federal cosmetic-specific concentration limit; state-level rules vary | Restricted concentration; nail hardener exception also exists under EU cosmetics law |
| DBP in cosmetics | Not restricted in cosmetics; restricted only in children’s toys and childcare articles [5][7] | Not restricted at the federal level | Banned outright in cosmetics and personal care products |
| “Free-of” label claims | No standardized definition or verification requirement | No standardized definition or verification requirement | No standardized definition or verification requirement |
The honest read: the EU is the only one of the three that has closed the DBP gap with a ban rather than a risk assessment, and none of the three regulators has stepped in to standardize what an “n-free” label has to mean.
Inform: What This Means for You
- If you work in a nail salon, the occupational health evidence is strong and worth acting on. Ventilation quality is the single biggest lever documented in the research, and it is reasonable to ask your workplace about it directly [2][4].
- Occasional home use is a lower-exposure category than daily occupational use, and most of the strongest harm data comes from the occupational group.
- TPHP absorption from a single manicure is real and measured, even if long-term consumer-level outcomes are still being studied. Gloves during at-home application measurably reduced absorption in the Duke/EWG study, which tells you the exposure route is dermal [3].
- Do not take a “3-free,” “5-free,” or “10-free” label at face value. Independent testing has repeatedly found these claims inaccurate, and no regulator verifies them before sale [8][9].
- In Canada specifically, DBP is not restricted in cosmetics the way it is in the EU. If avoiding DBP matters to you, the Canadian regulatory system will not do that filtering for you; you need to check the ingredient list yourself [5][7].
Improve: How to Reduce Exposure Without Giving Up Manicures
- Wear gloves when applying polish yourself. The Duke/EWG study found this measurably reduced TPHP absorption, since the exposure route is dermal, not inhaled [3].
- Ventilate the room during application and while polish dries, and avoid doing your nails in a small, closed bathroom.
- Check the actual ingredient list, not just the “free” number on the front label. Look for toluene, dibutyl phthalate, formaldehyde, and triphenyl phosphate by name, since the label claim alone has repeatedly failed to match the contents in independent testing [8][9].
- If you get manicures regularly, ask your salon about ventilation. The research consistently identifies inadequate ventilation as the single largest driver of occupational exposure, and salons that have addressed it show measurably lower air concentrations [2][4].
- Space out gel and acrylic appointments where possible, since these systems add UV exposure and different solvent chemistry on top of the plasticizer question covered here.
What This Does Not Mean
This is not a case for never getting a manicure again. The best-documented harm on this page, occupational respiratory and skin effects, falls on people exposed daily in poorly ventilated salons, not on someone painting their nails a few times a month. The TPHP absorption finding is real and worth knowing, particularly if you are pregnant or trying to conceive, but the long-term consumer-level health outcome is still an open question rather than a settled one. The most actionable point here is skepticism toward “free-of” labels specifically: that claim has been tested and found wanting often enough that reading the ingredient list yourself is a better strategy than trusting a marketing number on the front of the bottle.
FAQ
What is the “toxic trio” in nail polish?
Toluene, dibutyl phthalate (DBP), and formaldehyde, three ingredients that historically served as the solvent, plasticizer, and hardener in most nail polish formulas [1][2].
Is TPHP in nail polish dangerous?
TPHP, the common replacement for DBP, is confirmed to absorb into the body within hours of a single manicure and is an endocrine disruptor in animal studies. What has not yet been established is the long-term health effect of the exposure levels a typical consumer experiences [3].
Can I trust “10-free” or “13-free” labels?
Not fully. No regulator defines or verifies these claims, and peer-reviewed testing has found products marketed as free of specific chemicals that still contained them, sometimes at significant concentrations [8][9].
Is DBP banned in Canada?
Not in cosmetics. Canada restricts DBP in children’s toys and childcare articles but not in cosmetics or personal care products, unlike the EU, which bans it outright in cosmetics [5][7].
Are nail salon workers at higher risk than customers?
Yes, substantially. A 2025 systematic review found consistent evidence of occupational asthma, dermatitis, and other health effects tied to daily salon-level exposure, which is a different exposure category from occasional customer use [2][4].
The Bottom Line
Most nail polish has moved away from the exact toluene-DBP-formaldehyde combination once standard in the industry, but the most common replacement, TPHP, carries its own confirmed absorption and animal-study endocrine concerns [1][3]. The strongest evidence on this page is occupational: nail salon workers face real, well-documented respiratory and skin risks tied to daily exposure and inadequate ventilation [2][4]. For occasional home users, the practical risk is lower but not zero, and the most actionable finding here may be the least chemical one: “free-of” labels are unverified and have repeatedly failed independent testing, so reading the ingredient list yourself, in a country where DBP specifically is not restricted the way it is in the EU, is worth more than trusting the number on the front of the bottle [5][7][8][9].
Stay curious, stay critical.
Georden
References
- Occupational Safety and Health Administration. “Health Hazards in Nail Salons: Chemical Hazards.”
- Scott, L. et al. “The Safety of Nail Products: Health Threats in the Nail Industry.” International Journal of Dermatology (Wiley), 2025.
- Mendelsohn, E. et al. “Nail Polish as a Source of Exposure to Triphenyl Phosphate.” Environment International / Boston University School of Public Health.
- “The Nail Salon Workforce: A Systematic Scoping Review of Carcinogen Exposure Assessments, Health Outcome, and Workforce Intervention Research.” Reviews on Environmental Health / PubMed, 2025.
- Health Canada. “Cosmetic Ingredient Hotlist: Prohibited and Restricted Ingredients.”
- Thompson, J. et al. “Clearing the Air: A Pilot Study of Ventilation Interventions in New York City Nail Salons.” American Journal of Industrial Medicine (Wiley), 2025.
- David Suzuki Foundation. “Toxic Ingredient to Avoid: Dibutyl Phthalate.”
- Dodson, R. et al. “Phthalate and Organophosphate Plasticizers in Nail Polish: Evaluation of Labels and Ingredients.” Environmental Science & Technology (ACS) / PubMed.
- California Department of Toxic Substances Control. “Laboratory Study of Chemicals in Nail Products,” October 2023.
Georden Jones is the founder of The Peer Review. Read the full story.