Public defence Christina Christia 14/02/2023 - Characterization of occurrence, metabolism and contribution to human exposure of new plasticizers present in the indoor environment - Department Pharmaceutical Sciences
Openbare verdediging Christina Christia 14/02/2023 - Karakterisering van voorkomen, metabolisme en bijdrage aan menselijke blootstelling van nieuwe weekmakers aanwezig in het binnenmilieu - Departement Farmaceutische Wetenschappen
Promotoren: Prof. dr. Adrian Covaci - dr. Giulia Poma
Promotiezaal, gebouw Q - Campus Drie Eiken
Recently, several changes have been made to the chemical composition of products used indoors. Legacy chemicals have been replaced by “alternatives” due to evidence for adverse health effects of the former. However, there is still limited information related to the human exposure to these replacement chemicals. Therefore, there is urgent need to investigate their occurrence indoors and the extent of the human exposure to them. In this regard, this study was performed by recruiting twenty-five (n=25) families living in Flanders (Belgium). Two sampling campaigns were organized during winter and summer 2019 in the same households where paired samples of floor dust (n=25), handwipes (n=82) and urine (n=82) from adults and children (aged up to 7 years old) were collected.
Six alternative plasticizers named as, di-propylene glycol dibenzoate (DiPGDB), tri-n-butyl trimellitate (TBTM), bis-3,5,5-trimethyl hexyl phosphate (TMHPh), iso-octyl 2-phenoxy terephthalate (IOPhET), dimethyl azelate (DMA) and dimethyl sebacate (DMS) were detected for the first time in indoor dust after the application of a suspect screening analysis (SSA) workflow. These new plasticizers were then measured in dust using an in-house validated LC-MS/MS analytical method. Based on their levels, the plasticizers DiPGDB, TBTM, IOPhET and TMHPh were further selected to be investigated in handwipes. An innovative new analytical method was applied to the handwipes using a significantly lower amount of sample than reported in literature so far. The external human exposure through inadvertent dust ingestion and dermal absorption were estimated using the concentrations detected in dust and handwipes, respectively.
Finally, to provide an initial assessment of human exposure, the internal exposure to the new plasticizers was assessed for DiPGDB, TBTM and TMHPh, considering the abundancies in dust and handwipes and their theoretical bio-accessibilities. A combined workflow of an in-vitro assay using human liver microsomes (HLMs) and an in-silico prediction using a suitable software was applied and metabolites of Phase I were identified. Together with the predicted ones of Phase II, they were identified in the urine samples. An SSA workflow was employed using LC-QTOF-MS for the identification and semi-quantification.
The plasticizers DiPGDB and TBTM were the dominant plasticizers in dust and handwipes and their metabolites were found in higher levels in human urine. No risk was indicated via the inadvertent ingestion and dermal absorption of these compounds. Dust is a source of these new plasticizers but daily habits (eg. use of personal products) are likely contributing to the overall human exposure.