Urinary phthalate metabolites among workers in plastic greenhouses in western China

Agricultural plastic greenhouse (PG) production can extend the growing season of crops to satisfy domestic consumption in countries such as China. Workers in PGs have potential higher phthalate exposure risks than the general population as phthalate accumulation has been observed in greenhouse soil, air, and crops. To date, biomonitoring tests of phthalates for the working population have not been carried out. To address this shortage, we conducted a pilot study in Shaanxi Province, China, among 35 healthy PG workers by follow-up recording their seasonal dietary habits and work activities and urine sample collection and measurement between 2018 and 2019. The objectives were to uncover the association between phthalate metabolites and the population characteristics, seasonal and diurnal variations and causes, and to estimate exposure risks and contributions of exposure pathways from PG production systems. A total of 13 phthalate metabolite concentrations (Σ₁₃ phthalate metabolites) ranged from 102 to 781 (5th-95th) ng/mL (median: 300 ng/mL). Mono-n-butyl phthalate (MNBP) made up 51.3% of Σ₁₃ phthalate metabolites, followed by the sum of four di-2-ethylhexyl phthalate (DEHP) metabolites (24.2%), mono-2-isobutyl phthalate (MIBP) (13.4%), and mono-ethyl phthalate (MEP) (9.8%). The concentrations of MNBP and MIBP in summer were significantly higher than the levels in winter (p < 0.0001). A total of 62.3% of the PG worker population was shown to have exposure risks, and the proportion was as high as 79.4% in summer. Phthalate exposure of the workers from PG production systems constituted over 20% of the total creatinine-based daily intake, and consuming vegetables and fruit planted in PGs and inhalation in PGs were the two largest exposure pathways. Our findings demonstrate that it is important to protect workers in PGs from phthalate exposure risks, and phasing out the use of plastic materials containing phthalates in PGs is imperative, to guarantee food safety in PGs.