Cosmetic Preservatives: Hazardous Micropollutants in Need of Greater Attention?

In recent years, personal care products (PCPs) have surfaced as a novel class of pollutants due to their release into wastewater treatment plants (WWTPs) and receiving environments by sewage effluent and biosolid-augmentation soil, which poses potential risks to non-target organisms. Among PCPs, there are preservatives that are added to cosmetics for protection against microbial spoilage. This paper presents a review of the occurrence in different environmental matrices, toxicological effects, and mechanisms of microbial degradation of four selected preservatives (triclocarban, chloroxylenol, methylisothiazolinone, and benzalkonium chloride). Due to the insufficient removal from WWTPs, cosmetic preservatives have been widely detected in aquatic environments and sewage sludge at concentrations mainly below tens of mu g L-1. These compounds are toxic to aquatic organisms, such as fish, algae, daphnids, and rotifers, as well as terrestrial organisms. A summary of the mechanisms of preservative biodegradation by micro-organisms and analysis of emerging intermediates is also provided. Formed metabolites are often characterized by lower toxicity compared to the parent compounds. Further studies are needed for an evaluation of environmental concentrations of preservatives in diverse matrices and toxicity to more species of aquatic and terrestrial organisms, and for an understanding of the mechanisms of microbial degradation. The research should focus on chloroxylenol and methylisothiazolinone because these compounds are the least understood.

Automated summary

In recent years, personal care products (PCPs) have been identified as a new class of pollutants that pose potential risks to non-target organisms when released into wastewater treatment plants and receiving environments. This paper reviews the occurrence, toxicological effects, and microbial degradation mechanisms of four selected preservatives commonly found in PCPs. The presence of these preservatives has been widely detected in aquatic environments and sewage sludge due to insufficient removal from WWTPs. They have been found to be toxic to aquatic and terrestrial organisms, but formed metabolites are generally less toxic than the parent compounds. Further research is needed to assess the environmental concentrations and toxicity of preservatives in diverse matrices and to understand the microbial degradation mechanisms. Focus should be given to the least understood preservatives, chloroxylenol and methylisothiazolinone.