Occurrence and distribution of phthalate esters and microplastics in wastewater treatment plants in Taiwan and their toxicological risks

Phthalate esters (PAEs) are fat soluble synthetic chemicals, usually regarded as plasticizers for being added in numerous plastic products. Thus, environmental and health hazards of PAEs are associated with increasing plastic pollution. In this study, PAEs from sludge samples collected from water, sewage, and industrial treatment plants (N = 17) were analyzed using Gas Chromatography/Mass Spectrometry. Microplastics (MPs) were also quantified and correlated with PAEs. Results showed the highest average PAE concentrations in sewage treatment plants. The greatest Sigma PAEs concentration were found in sewage treatment plant (STP4) with 32,414 mu g/kg dw, while the lowest found in water treatment plant (WTP3) with 2062 mu g/kg dw. Among different PAEs, di-(2-ethyl hexyl) phthalate (DEHP) contributes the highest. Similarly, DEHP, di-n-octyl phthalate (DnOP) and diisononyl phthalate (DiNP) significantly correlated with the total PAEs indicating their large contribution to sludge contamination. The abundance of microplastics in sludge ranged between 1 and 7 MP/g, highest at ITP6, but not detected in some stations. While microplastics may potentially increase PAEs, there was no significant relationship between Sigma PAEs and MP abundance. The estimated human daily intake of DEHP and di-n-butyl phthalate (DnBP) when contaminated sludge be used showed low toxicological risks to exposed adults. This research presents the sludge characteristics, PAEs, and microplastic concentrations in different wastewater treatment plants in Taiwan. PAE contamination was highly contributed by domestic and industrial wastes shown by their significant amounts in STP and ITP. Results further provide evidence for potential sludge recycling (WTP sludge) and application to soil.

Automated summary

This study analyzed the concentrations of phthalate esters (PAEs) and microplastics (MPs) in sludge samples collected from different wastewater treatment plants in Taiwan. The results showed that the highest PAE concentrations were found in sewage treatment plants, with DEHP being the main contributing substance. The abundance of microplastics in sludge varied among different samples, but showed no significant correlation with PAE concentrations. The estimated toxicological risks to exposed adults from DEHP and DnBP in contaminated sludge were found to be low.