Elsevier

Science of The Total Environment

Volume 656, 15 March 2019, Pages 862-869
Science of The Total Environment

Spatial distribution and mass loading of phthalate esters in wastewater treatment plants in China: An assessment of human exposure

https://doi.org/10.1016/j.scitotenv.2018.11.458Get rights and content

Highlights

  • PAE levels in sludges from 46 WWTPs in 22 provinces, China were investigated.

  • DEHP was the most abundant PAE congener in sludge.

  • The spatial distribution of PAEs in sludges was similar to that in indoor dusts.

  • Human exposure to PAEs through sludge application in soil is minor.

Abstract

The occurrence and fate of nine phthalate esters (PAEs), including dimethyl phthalate (DMP), diethyl phthalate (DEP), di‑n‑butyl phthalate (DBP), di-isobutyl phthalate (DIBP), benzyl butyl phthalate (BzBP), di (2‑ethylhexyl) phthalate (DEHP), di‑n‑hexyl phthalate (DNHP), dicyclohexyl phthalate (DCHP), and di‑n‑octyl phthalate (DNOP), in sludges collected from 46 wastewater treatment plants (WWTPs) from 22 Chinese provinces were investigated. The nine PAEs were detected in almost all the sludge samples. DEHP was the most abundant congener in all sludge samples, followed by DBP and DIBP. The DEHP concentrations in sludge were in the range of 0.326–67.8 (mean: 14.7) μg/g dry weight (dw), which were at the lower bound or middle of the concentration range of DEHP in sludge globally (0.0200–3514 μg/g dw). Spatial distribution and mass loading of PAEs in WWTPs were investigated. The concentrations of Σ9PAEs in sludges from different provinces were in the order as follows: Jilin (40.2 μg/g dw) > Liaoning (38.9 μg/g dw) > Beijing (30.7 μg/g dw), while the mass loading of ∑9PAEs in sludges were Guangdong (10.1 tons/yr) > Liaoning (9.97 tons/yr) > Shandong (5.59 tons/yr). Our study showed that the geographical distribution of PAEs in sludges was similar to that in indoor dusts found in earlier study, suggesting the existence of a common source for these chemicals in both matrices. Based on the concentrations measured, human exposure to PAEs through sludge application in soil was evaluated and the exposure dose is minor.

Introduction

With the development of industrialization and urbanization, large amount of sewage has been generated in China. Sludge is the by-product of industrial wastewater or wastewater treatment processes, and it contains relatively high levels of organic materials (40–80% dry weight) (Yang et al., 2011). In China, the total production of sludge has reached to 6.25 million tons in 2013, and the average annual growth from 2007 to 2013 was 13% (Yang et al., 2015). Such large amount of sludge has become a big environmental issue and caused public concern. However, in China sludge disposal is generally improper, and it is estimated that >80% of sludge is disposed by improper dumping in 2013 (Yang et al., 2015). Therefore, sludge treatment and disposal have challenged the development of the wastewater treatment industry and environmental protection in China. Land application of sludge has become a good option for the management of sludge in many countries (Smith, 2009). In European countries, the percentage of reused agricultural sludge reaches levels as high as 50% in Germany, 54% in Spain, 65% in France and 71% in the United Kingdom (Magoarou, 2000). Although sludge has been widely used in agriculture, rigorous assessment is required as various contaminants existing in sludge may have adverse effect on crops or soils.

So far, various toxic contaminants have been found in sludge, including heavy metals, polycyclic aromatic hydrocarbons, organochlorine pesticides, polychlorinated biphenyls, polybrominated diphenyl ethers, bisphenol analogues and phthalate esters (PAEs) (Cai et al., 2007; da Silva Oliveira et al., 2007; Meng et al., 2016; Meng et al., 2014; Song et al., 2014), which can cause serious environmental pollution. PAEs are high-production volume chemicals and their annual production was estimated at levels of over 1.4 million tons per year in China in 2016 (Gong et al., 2008). PAEs are commonly used as plasticizers in consumer products like polyvinyl chloride (PVC) plastics, food packaging, and personal care products. PAEs possess endocrine disrupting properties, and studies have linked PAEs to several health issues (Wenzel et al., 2018; Yin et al., 2018; Wang et al., 2018). For example, several PAEs are known antiandrogenic endocrine disruptors, which raise concern for prenatal exposure during critical windows of fetal development (Wenzel et al., 2018). Diethyl phthalate (DEP) and dibutyl phthalate (DBP) can affect the early stages of embryonic development (Yin et al., 2018). Besides, epidemiologic reports demonstrated that di (2-ethylhexyl) phthalate (DEHP) has a positive relationship with allergic diseases, and animal studies further indicated that maternal exposure to DEHP during pregnancy and lactation aggravated pulmonary inflammation of the rat offspring (Wang et al., 2018). Since humans are widely exposed to PAEs, PAEs and their metabolites have also been frequently detected in human urine, serum or breast milk (Högberg et al., 2008; Jiping Zhu et al., 2006; Wenzel et al., 2018). Once pregnant women are exposed to PAEs, these chemicals undergo rapid metabolism in a few hours or days. Thus, PAE metabolites that are generally more toxic than their parent compounds, can be transmitted to fetuses before birth and may affect the health of fetuses (Li et al., 2018).

PAEs have been reported to occur in various environmental matrices (Gao and Wen, 2016), including dust (Guo and Kannan, 2011; Larsson et al., 2017), air (Tran et al., 2017; Zhang et al., 2014), water (Chepchirchir et al., 2017; Zeng et al., 2008), soil (Zhao et al., 2018) and sediment (Zeng et al., 2008). Sludge is one of the significant sources of PAEs to the environment, and measurement of PAEs levels in sludge can help to clarify the flow of PAEs between human and the environment (Meng et al., 2014). PAEs are abundant in sludge from European and North American countries, such as Canada (Bright and Healey, 2003), Spain (Aparicio et al., 2007), Germany (Fromme et al., 2002), and Denmark (Roslev et al., 2007), at concentrations of 0.020–3514 μg/g dry weight (dw). There are a few studies concerning PAEs in sludges from China. PAEs were found in sludges collected from 11 WWTPs of mainland and Hong Kong, China at concentrations ranging from 10 to 114 μg/g dw (Cai et al., 2007). Meng et al. (2014) analyzed sixteen PAE congeners in sludges from Shanghai, China, and found extremely high concentrations (1350 μg/g dw) of PAEs in sludges from WWTPs of industrial origin. However, information about PAE pollution in sludge on a national scale in China is scant. A nationwide research related to PAEs in sludge may help to determine the quality of sludge in land application and to supplement the data with respect to human exposure to PAEs derived from the sludge application.

In this study, sludge samples collected from 46 WWTPs in 22 provinces, China, were analyzed by gas chromatography-tandem mass spectrometry (GC–MS/MS) for nine PAEs, viz., dimethyl phthalate (DMP), DEP, DBP, di-isobutyl phthalate (DIBP), benzyl butyl phthalate (BzBP), DEHP, di-n-hexyl phthalate (DNHP), dicyclohexyl phthalate (DCHP), and di-n-octyl phthalate (DNOP). The objectives of this study were to (1) determine the concentrations and profiles of nine PAE congeners in sludge from China, (2) trace the source of PAEs in sludge, and (3) evaluate the potential human exposure to PAEs through sludge application in soil.

Section snippets

Sampling

Sludge samples were collected from 46 WWTPs in 22 provinces, China in January 2017 and 2018. Descriptive information of each sample including the sampling locations and characteristics is provided in Table S1 (Supporting information). Approximately 3 kg wet weight of each sludge sample was collected in WWTPs, sealed in aluminum foil, and then directly transported to the laboratory. The samples were freeze-dried, homogenized, sieved with the 180 μm sieve, and kept at −20 °C until analysis.

Standards and reagents

The

Levels and spatial distributions of PAEs in sludges

Summary statistics for the PAE concentrations measured in sludges is listed in Table 1, and detailed results of measured concentrations for each sludge sample are presented in Table S1. We defined Σ9PAEs as the sum concentration of all nine target PAEs. DEHP was found in all samples analyzed (n = 46). DIBP and DBP were found in >95.0% of the samples and DMP, DEP, and BzBP were found in >80.0% of the samples. The detection ratios of DCHP and DNOP were 56.5% and 63.0%, respectively. Six of nine

Conclusions

The concentrations and distributions of nine PAE congeners in sludges collected from 46 WWTPs in 22 provinces, China were investigated. The concentrations of DEHP in sludge in the present study were at the lower bound or middle of the concentration range of DEHP in sludge globally. DEHP was the dominant PAE congener in sludge, followed by DBP and DIBP. Composition analysis of PAEs in sludges suggests the existence of a common source. Distinct geographical difference of PAE concentrations in

Acknowledgements

This work was jointly supported by the National Natural Science Foundation of China (grant numbers 21522706, 21677167 and 21806172), the Fundamental Research Funds for the Central Universities (grant number 2014 MS122) and the Thousand Young Talents Program of China.

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