Toxicological assessment of phthalates and their alternatives using human keratinocytes

Phthalates are mainly used as binders and plasticizers in various industrial products including detergents, surfactants, waxes, paints, pharmaceuticals, food products, and cosmetics. However, they have been reported to be endocrine disruptors, which are chemicals that can mimic or disturb endocrines, causing interference to the endocrine system. Recently, there have been numerous reports showing that phthalates have negative health impacts such as asthma, breast cancer, obesity, type II diabetes, and male infertility. Due to these effects, there is an urgent need for phthalate alternatives. In this study, the potential cytotoxicity of phthalates and their substitutes were screened in HaCaT cells, a human keratinocyte cell line, using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) thiazolyl blue assay, immunocytochemistry, flow cytometric analysis, and western blotting. We confirmed that common phthalates such as butyl benzyl phthalate (BBP), di-n-butyl phthalate (DBP), and di-2-ethylhexyl phthalate (DEHP) have genotoxic effects, leading to cell death. Among the known phthalate substitutes, tributyl O-acetylcitrate (ATBC), triethyl 2-acetylcitrate (ATEC), and trihexyl O-acetylcitrate (ATHC) were tested for cytotoxicity. As a result, ATEC showed similar levels of cytotoxicity with the phthalates whereas ATBC and ATHC did not show significant cytotoxicity even in high doses (5 mg/ml).