In an article published on August 5, 2022, in the International Journal of Hygiene and Environmental Health, Benedikt Ringbeck from the Institute for Prevention and Occupational Medicine of the Ruhr-University Bochum (IPA), Germany, and co-authors determined the nonylphenol (NP, CAS 25154-52-3) exposure of the German population over the past 30 years.
The authors quantified the levels of the two oxidized NP metabolites hydroxy-NP (OH-NP) and oxo-NP as novel NP exposure biomarkers in 660 urine samples from the German Environmental Specimen Bank (ESB) collected between 1991 and 2021 from 20 to 29-years old male and female students. Based on the urinary levels of OH-NP and the 24 h urine volume, the daily intakes were calculated.
Ringbeck and co-authors reported that the levels of the two metabolites “correlated strongly” with lower oxo-NP levels due to a lower metabolic conversion. From 1991 to 2021, median urinary OH-NP concentrations decreased significantly from 4.32 µg/L to 0.70 µg/L. Also, the frequency of detection decreased: while OH-NP could be quantified in all samples taken until 2017, it was found in 90% and 77% of the samples from 2019 and 2021, respectively, in concentrations above the level of quantification. The daily intakes of NP were calculated to be 0.16 µg/kg body weight (bw) per day in 2019 and 0.04 µg/kg bw per day in 2021. Accordingly, the intake decreased by about 4-times over the 30 years. The authors observed that “the major drop took place only after 2012. This came as a surprise because strict restrictions had been enacted much earlier in the EU, in 2003.” The Danish Environmental Agency set a provisional tolerable daily NP intake of 5 µg/kg bw which was never exceeded in the German cohort. Since the calculated intake roughly corresponded to the average daily NP intake predictions via foodstuff the authors postulate that “this points to foodstuff as a major source of exposure.”
Given the ongoing use of NP worldwide, the scientists urge to continue monitoring NP exposure nationally and globally in the future. This would help to better understand the time lag between regulatory restrictions and lower exposure levels as well the exposure of more susceptible population groups, such as children and pregnant women, and to better elucidate exposure sources and uptake routes of NP.
NP is an endocrine disrupting chemical (EDC) and a typical non-intentionally added substance (NIAS) since it is a break-down product of trisnonylphenylphosphite (TNPP) which is used as antioxidant and stabilizer in plastics. In July 2019, the European Chemicals Agency (ECHA) added TNPP to the REACH Candidate List of substances of very high concern (SVHCs) for authorization due to its endocrine-disrupting properties (FPF reported). In the last year, the US state of Maine published a list of food contact chemicals of high concern. NP is one of the 10 listed chemicals (FPF reported).
Reference
Ringbeck B. et al (2022). “Nonylphenol (NP) exposure in Germany between 1991 and 2021: Urinary biomarker analyses in the German Environmental Specimen Bank (ESB).” International Journal of Hygiene and Environmental Health. DOI: 10.1016/j.ijheh.2022.114010
