In their study, the scientists looked at quaternary ammonium compounds (QACs) that are used in many household cleaning goods.

Hair conditioning industry has largely developed since then, and hair care products began to include ammonium compounds, silicon, fatty alcohols, and so on.

Common mixtures include sodium citrates, sodium borohydride (also used to bleach wood pulp) and ammonium compounds, all of which can be toxic to humans and the environment.