Trends of Nonylphenol Exposure in an Australian Population Based on Urinary Metabolite Analysis

Nonylphenol (NP) is an alkylphenol primarily used to synthesize nonylphenol ethoxylates (NPEO) and tris(4-nonylphenyl) phosphite (TNPP) which are extensively used in industrial and consumer products. NP and its derivatives are well-known endocrine disruptors and are associated with other toxic effects, raising concerns regarding exposure. This study assessed NP exposure in an Australian population by quantifying two specific urinary NP metabolites (OH-NP and oxo-NP) in age- and sex-stratified pooled urine samples collected in 2014-2015 and 2022-2023 (48 pools representing 4,800 individuals). OH-NP (major metabolite) was detected in all pools, with urinary levels and calculated daily intakes (DIs) approximately four times lower in 2022/23 than in 2014/15. OH-NP urinary levels and DIs decreased with age in females, while no age-related trend was observed in males. Male children and female children had similar exposure levels, while sex-related differences were more pronounced in adults (males>females). When combining all ages, males exhibited higher intakes than females. On average, DIs calculated from the pooled samples suggest no appreciable risk from NP exposure in the studied Australian population. However, potential high individual exposures within a pool and uncertainties due to limited knowledge of isomer-specific toxicokinetics and human isomer profiles should be acknowledged.