Body & Beauty / Compounds / Bronopol (2-bromo-2-nitropropane-1,3-diol)

Bronopol (2-bromo-2-nitropropane-1,3-diol) on your skin: a safety profile

Low risk

Dermal contact with bronopol in cosmetic products at permitted concentrations (≤0.1%) presents low direct dermal sensitization risk — sensitization rates in clinical patch test series are lower than for isothiazolinones or formaldehyde releasers. However, the concern about nitrosamine formation in the finished product means that the dermal exposure of greatest concern is not to bronopol itself but potentially to any N-nitrosamines formed in the product during manufacturing or storage. N-Nitrosamines including NDELA are absorbed through intact skin and have demonstrated systemic carcinogenicity in rodents via dermal application. FDA and EU regulatory guidance requires testing of finished bronopol-containing products for nitrosamine content when amine raw materials are present in the formulation. Products properly formulated to avoid amine co-ingredients and tested to confirm absence of nitrosamine formation present very low dermal hazard from bronopol itself. Occupational exposure of workers in bronopol manufacturing and in cosmetics manufacturing (during bronopol addition to formulations) requires standard protective equipment, as concentrated bronopol solutions are strong oxidizers and irritants.

What is bronopol (2-bromo-2-nitropropane-1,3-diol)?

The IUPAC name is 2-bromo-2-nitropropane-1,3-diol.

Also known as: 2-bromo-2-nitropropane-1,3-diol, bronopol, 2-Bromo-2-nitro-1,3-propanediol, Bronosol.

IUPAC name
2-bromo-2-nitropropane-1,3-diol
CAS number
52-51-7
Molecular formula
C3H6BrNO4
Molecular weight
199.99 g/mol
SMILES
C(C(CO)([N+](=O)[O-])Br)O
PubChem CID
2450

Risk for people

Low risk

Dermal contact with bronopol in cosmetic products at permitted concentrations (≤0.1%) presents low direct dermal sensitization risk — sensitization rates in clinical patch test series are lower than for isothiazolinones or formaldehyde releasers. However, the concern about nitrosamine formation in the finished product means that the dermal exposure of greatest concern is not to bronopol itself but potentially to any N-nitrosamines formed in the product during manufacturing or storage. N-Nitrosamines including NDELA are absorbed through intact skin and have demonstrated systemic carcinogenicity in rodents via dermal application. FDA and EU regulatory guidance requires testing of finished bronopol-containing products for nitrosamine content when amine raw materials are present in the formulation. Products properly formulated to avoid amine co-ingredients and tested to confirm absence of nitrosamine formation present very low dermal hazard from bronopol itself. Occupational exposure of workers in bronopol manufacturing and in cosmetics manufacturing (during bronopol addition to formulations) requires standard protective equipment, as concentrated bronopol solutions are strong oxidizers and irritants.

Regulatory consensus

14 regulatory and scientific bodies have classified Bronopol (2-bromo-2-nitropropane-1,3-diol). The classifications differ — that's the data.

AgencyYearClassificationNotes
US EPA2000not classifiable as to human carcinogenicity (Group D)
EFSA2010not evaluated for carcinogenicity as standalone; nitrosamine formation in bronopol-containing cosmetic formulations regulated under EU Cosmetics Regulation Article 15 which prohibits placing cosmetics containing nitrosamines on the market; SCCS opinion notes that bronopol's genotoxicity concern derives from nitrosamine formation in the finished product, not intrinsic carcinogenicity of bronopol itself; maximum 0.1% in cosmetics (Annex V No. 34)
EPA CTX / EPA OPP—Group E Evidence of Non-carcinogenicity for Humans
EPA CTX / Genetox—Genotoxicity: negative (Ames: negative, 0 positive / 3 negative reports)
EPA CTX / Genetox—Genotoxicity: negative (Ames: negative, 0 positive / 3 negative reports)
EPA CTX / Skin-Eye—Eye Irritation: Eye Dam. 1 (score: very high)
EPA CTX / Skin-Eye—Skin Irritation: Skin Irrit. 2 (score: high)
EPA CTX / Skin-Eye—Skin Sensitization: Sh (score: high)
EPA CTX / Skin-Eye—Eye Irritation: Category 1 (score: very high)
EPA CTX / Skin-Eye—Skin Irritation: Category 2 (score: high)
EPA CTX / Skin-Eye—Eye Irritation: Category 8.3A (Category 1) (score: very high)
EPA CTX / Skin-Eye—Skin Irritation: Category 6.3A (Category 2) (score: high)
EU BPR—Approved active substance for multiple biocidal product types
EU Cosmetics—Allowed in cosmetics at ≤0.1%. Must be labeled. Cannot be used with amines (nitrosamine concern)

Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.

Where you encounter bronopol (2-bromo-2-nitropropane-1,3-diol)

  • Industrial Facilities — Manufacturing plants, Chemical storage areas, Waste treatment sites
  • Occupational Environments — Factories, Warehouses, Transportation vehicles
  • Personal Care — shampoo, conditioner, lotion, cosmetics, sunscreen
  • Pharmaceutical — Ophthalmic solutions, Topical medications
  • Industrial — Paper mill slimicide, Oil field biocide, Metalworking fluid preservative, Latex paint preservative

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Bronopol (2-bromo-2-nitropropane-1,3-diol):

  • Physical/mechanical pest control (IPM)
    Trade-offs: More labor-intensive. May not be sufficient for severe infestations.
    Relative cost: 1.2-2×
  • Phenoxyethanol
    Relative cost: 1.2-2×
  • Organic acids
    Relative cost: 2-5× conventional
  • Ethylhexylglycerin
    Trade-offs: Alternative approach; specific tradeoffs depend on application context, scale, and regulatory requirements. Full hazard assessment of alternative recommended before adoption to avoid regrettable substitution.
    Relative cost: 1.2-2×

Frequently asked questions

Is bronopol (2-bromo-2-nitropropane-1,3-diol) safe for you?

Dermal contact with bronopol in cosmetic products at permitted concentrations (≤0.1%) presents low direct dermal sensitization risk — sensitization rates in clinical patch test series are lower than for isothiazolinones or formaldehyde releasers. However, the concern about nitrosamine formation in the finished product means that the dermal exposure of greatest concern is not to bronopol itself but potentially to any N-nitrosamines formed in the product during manufacturing or storage. N-Nitrosamines including NDELA are absorbed through intact skin and have demonstrated systemic carcinogenicity in rodents via dermal application. FDA and EU regulatory guidance requires testing of finished bronopol-containing products for nitrosamine content when amine raw materials are present in the formulation. Products properly formulated to avoid amine co-ingredients and tested to confirm absence of nitrosamine formation present very low dermal hazard from bronopol itself. Occupational exposure of workers in bronopol manufacturing and in cosmetics manufacturing (during bronopol addition to formulations) requires standard protective equipment, as concentrated bronopol solutions are strong oxidizers and irritants.

What products contain bronopol (2-bromo-2-nitropropane-1,3-diol)?

Bronopol (2-bromo-2-nitropropane-1,3-diol) appears in: Manufacturing plants (Industrial facilities); Chemical storage areas (Industrial facilities); Factories (Occupational environments); Warehouses (Occupational environments); shampoo (Personal care).

Why do regulators disagree about bronopol (2-bromo-2-nitropropane-1,3-diol)?

Bronopol (2-bromo-2-nitropropane-1,3-diol) has been classified by 14 agencies including US EPA, EFSA, EPA CTX / EPA OPP, EPA CTX / Genetox, EPA CTX / Genetox, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.

See Bronopol (2-bromo-2-nitropropane-1,3-diol) in the body app

Look up products containing bronopol (2-bromo-2-nitropropane-1,3-diol), compare to alternatives, and explore the full data record.

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Sources (2)
  1. US EPA Bronopol: Group D Not Classifiable; FIFRA Antimicrobial; Nitrosamine Formation with Amines; NDELA IARC 2B; FDA 1992 Guidance Minimize Amine Co-formulation; Contact Sensitizer; Aquaculture Parasite Treatment (2000) — regulatory
  2. EFSA/SCCS Bronopol: EU Cosmetics Regulation Annex V No. 34 Maximum 0.1%; Nitrosamine Prohibition <50 ppb; Article 15 N-Nitroso Restriction; Aquatic LC50 2–10 mg/L; Aquaculture Biocide Environmental Concern; Algal EC50 <1 mg/L (2010) — regulatory

Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →