Urinary di-(2-ethylhexyl) phthalate metabolites are independently related to serum neurofilament light chain, a biomarker of neurological diseases, in adults: results from NHANES 2013–2014

Di (2-ethylhexyl) phthalate (DEHP) is a chemical commonly used in the manufacturing of plastics and can pose human health risks, including endocrine disruption, reproductive toxicity, and potential carcinogenic effects. Children may be particularly vulnerable to the harmful effects of DEHP. Early exposure to DEHP has been linked to potential behavioral and learning problems. However, there are no reports to date on whether DEHP exposure in adulthood has neurotoxic effects. Serum neurofilament light chain (NfL), a protein released into the blood after neuroaxonal damage, has been shown to be a reliable biomarker for many neurological diseases. To date, no study has examined the relationship between DEHP exposure and NfL. For the present study, we selected 619 adults (aged ≥ 20 years) from the 2013–2014 National Health and Nutrition Examination Survey (NHANES) to examine the association between urinary DEHP metabolites and serum NfL. We reported higher urinary levels of ln-mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), ln-mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), and ln-mono(2-ethyl-5-carboxypentyl) phthalate (MECPP), and ln-ΣDEHP levels were associated with higher serum levels of ln-NfL (ΣDEHP: β-coefficient = 0. 075; S.E. = 0.026; P = 0.011). When we divided ΣDEHP into quartiles, mean NfL concentrations increased with quartiles of MEHHP ( P for trend = 0.023). The association was more pronounced in males, non-Hispanic white race, higher income, and BMI < 25. In conclusion, higher DEHP exposure was positively associated with higher serum NfL in adults from NHANES 2013–2014. If this finding is causal, it is possible that DEHP exposure in adulthood may also induce neurological damage. Although the causality of this observation and the clinical significance are uncertain, our findings suggest that additional research is needed on DEHP exposure, serum NfL, and neurological disease in adults.