An updated weight of evidence approach for deriving a health-based guidance value for 4-nonylphenol

4-Nonylphenol (NP) is a persistent estrogen-active compound. Human exposure to NP is primarily through water and food. Although risk assessments of NP have been conducted by the European Union and a few other countries, only the Danish Veterinary and Food Administration, in 2000, proposed a tolerable daily intake of 0.005 mg kg−1 body weight (bw) day−1. New data have been accumulated since then, prompting an update on the risk assessment of NP. A weight of evidence approach is recommended for use in scientific assessments by several agencies, e.g., European Food Safety Authority, etc. Based on the results of a weight of evidence approach, two methods were used to derive the health-based guidance value (HBGV) for NP in this study, namely a no observed adverse effects level/lowest observable adverse effect level method, and a benchmark dose method. Considering the considerable uncertainty of benchmark dose model fitting of the available data, a tolerable daily intake value of 0.025 mg kg−1 bw day−1 was derived as a provisional HBGV for NP based on the lowest observable adverse effect level value of 15 mg kg−1 bw day−1 of the renal toxicity in rats, together with the uncertainty factor of 600. However, the HBGV of NP still needs further investigation.