The release of formaldehyde upon decomposition of 2-bromo-2-nitropropan-1,3-diol (Bronopol)

We investigated the release of formaldehyde (FA) upon the decomposition of 2-bromo-2-nitropropan-1,3-diol (Bronopol: BP), an FA-releasing substance widely used as an antimicrobial preservative in cosmetics and toiletries in many Western countries. The decomposition process producing FA mainly depends on temperature and pH. Notably, the pH of the BP-diluted buffer solution was the factor most influencing the release of FA. The release was markedly in higher alkaline buffer compared with acidic buffer. When a BP solution [0.1 % (w/v)] prepared with a weakly alkaline buffer (pH 8.0) was stored at 25 degrees C, the concentration of FA reached 30 ppm after 24 hr. On the other hand, under acidic conditions (pH 2.0), little FA was produced over 50 days. Homemade cosmetics (lotions and jells) were made [with 0.1 % (w/v) BP] and stored at a constant temperature of 25 degrees C for 30 days. The concentration of FA increased with time, reaching 20 ppm after 50 days. We investigated seasonal variation in the release of FA upon decomposition of BP in Osaka. BP test solution [0.1% (w/v)] was prepared with 0.005 M sodium phosphate buffer (pH 6.0) and stored at ambient temperature for 30 days. The experiment was conducted three times in different seasons (mid winter, early spring, and early summer). It was found that the release of FA with decomposition of BP differed among the seasons.