Safety

Bronopol: Allergy, Toxicity & Environmental Impact — A Factual Review

Responsible use of any industrial preservative requires understanding its human health and environmental profile alongside its performance benefits. This page summarises the documented occupational allergy, acute toxicity, and aquatic toxicity data for Bronopol based on published toxicological literature and safety data sheets.

Published 2026-01-20Updated 2026-07-27By Vasudev Chemo Pharma Technical TeamReviewed by Vasudev Chemo Pharma EHS & Quality Team, Industrial Safety, GHS Classification

Is Bronopol a Known Skin Allergen?

Yes. Bronopol was the 15th-most-prevalent allergen in patch tests (3.4%) among people with suspected allergic contact dermatitis in a 2005-2006 study. It is commonly found in skin and personal care products and topical medications.

Bronopol allergy is not typically the leading cause of contact dermatitis compared to other common allergens, but a different risk profile is observed in people with serious skin diseases such as chronic eczema or atopic dermatitis, where impaired skin barrier function and increased use of specialised skincare products elevate sensitisation risk. The specificity of allergic reactions to Bronopol is attributed primarily to decomposition products such as 2-bromoethanol, 2-bromo-2-nitroethanol, and bromonitromethane, rather than to formaldehyde specifically, though documented cross-reactivity with established formaldehyde allergy has also been reported.

What Is Bronopol's Acute Toxicity Profile?

Published data lists Bronopol's oral LD50 in rats at approximately 180-305 mg/kg and dermal LD50 in rats at approximately 1,600 mg/kg, consistent with its GHS acute toxicity Category 4 classification (harmful if swallowed or in contact with skin).

Additional cited data includes an oral LD50 of approximately 270 mg/kg in mice and 250 mg/kg in dogs. These values place Bronopol's acute toxicity in a moderate range consistent with its GHS Category 4 classification, notably lower in acute hazard than substances classified in Category 1-3, though still requiring standard handling precautions. No component of Bronopol-containing products at levels of 0.1% or greater is identified as a probable, possible, or confirmed human carcinogen by IARC, ACGIH, OSHA, or NTP according to published safety data sheet information.

Is Bronopol Toxic to Aquatic Life?

Yes. Bronopol is classified as very toxic to aquatic life with long-lasting effects (H410). Published data cites a fish LC50 of approximately 20-41 mg/L (96-hour, rainbow trout) and a Daphnia magna EC50 of approximately 1.4-1.6 mg/L (48-hour).

This aquatic toxicity classification underlies the specific handling guidance to prevent Bronopol or contaminated wash-water from entering drains, waterways, or soil. Additional cited ecotoxicity data notes moderate-to-high toxicity to estuarine and marine invertebrates and slight toxicity to marine fish and birds under acute oral exposure, though a comprehensive quantitative risk assessment covering all exposure routes has not been universally published. In the United States, the risk to the aquatic environment from Bronopol-containing products is addressed under the NPDES (National Pollutant Discharge Elimination System) permitting programme, and labels on Bronopol-containing products are required to meet NPDES requirements where applicable.

Bronopol acute and aquatic toxicity summary
Endpoint	Value	Species / test
Oral LD50	180-305 mg/kg	Rat
Dermal LD50	~1,600 mg/kg	Rat
Fish LC50 (96h)	~20-41 mg/L	Rainbow trout (Oncorhynchus mykiss)
Daphnia EC50 (48h)	~1.4-1.6 mg/L	Daphnia magna

Frequently asked questions

Is Bronopol a common cause of contact dermatitis?+

Bronopol was documented as the 15th-most-prevalent allergen in patch tests (3.4%) among people with suspected allergic contact dermatitis in a 2005-2006 study — a real but not leading contact allergen compared to other common substances.

What is the oral LD50 of Bronopol?+

Published data lists the oral LD50 of Bronopol in rats at approximately 180-305 mg/kg, consistent with its GHS acute toxicity Category 4 classification (harmful if swallowed).

Is Bronopol toxic to fish and aquatic invertebrates?+

Yes. Bronopol carries GHS classification H410 (very toxic to aquatic life with long-lasting effects), with published data citing a fish LC50 of approximately 20-41 mg/L and a Daphnia magna EC50 of approximately 1.4-1.6 mg/L.

Is Bronopol considered a human carcinogen?+

According to published safety data sheet information, no component of Bronopol-containing products at levels of 0.1% or greater is identified as a probable, possible, or confirmed human carcinogen by IARC, ACGIH, OSHA, or NTP.