Bronopol (INN) is an organic compound that is used as an antimicrobial. It is a white solid although commercial samples appear yellow. Bronopol was invented by The Boots Company PLC in the early 1960s and first applications were as a preservative for pharmaceuticals. Owing to its low mammalian toxicity (at in-use levels) and high activity against bacteria (especially the troublesome Gram-negative species), bronopol became popular as a preservative in many consumer products such as shampoos and cosmetics. It was subsequently adopted as an antimicrobial in other industrial environments such as paper mills, oil exploration and production facilities, as well as cooling water disinfection plants.