Bronopol is used as a preservative in various cosmetic, pharmaceutical, toiletry and household preparations at concentrations of up to 0.1% (wt/vol) particularly because of its high activity against Gram-negative bacteria, especially Pseudomonas aeruginosa and other pseudomonad. Bronopol hydrolyzes within 3 h at 60 °C and pH 8, producing formaldehyde, nitrosamines, and other molecules. Although the parent compound (bronopol) is rather short-lived in the environment, its degradation products are toxic and more persistent. The protection against the bactericidal activity of bronopol afforded by catalase or superoxide dismutase suggests that the activity stems from the aerobic interaction and the generation of active oxygen species from oxygen diffusing into the suspensions during bronopol treatment. The acute oral LD50 was 307 mg/kg for rat males and 342 mg/kg for females. Bronopol is moderately toxic by the oral route. Results from an acute dermal toxicity study while inadequate, suggest bronopol is highly toxic by the dermal route.