September 19, 2002

Alkylphenols Bulletin:
NEW STUDIES SUPPORT SAFETY OF NONYLPHENOL

The Alkylphenols Bulletin periodically notifies manufacturers and users of alkylphenols and their derivatives of national and international developments of interest. For further information, please contact the APE Research Council at the address below.

Recent studies have significantly expanded the database of knowledge supporting the safety of nonylphenol (NP), used to make tris(nonylphenyl)phosphite (TNPP), a plastics additive, and nonylphenol ethoxylate (NPE) commonly used in cleaning products. A new report from the UN International Program on Chemical Safety (IPCS) concluded that the evidence for ANY chemical having harmful effects on the human endocrine system is weak, due to inconsistent and inconclusive results, and called for more studies, especially on possible "low-dose" effects. New studies (Moffat et al., 2001; Doerge et al., 2002; Green et al., manuscript in preparation) support the human safety of NP by confirming that only high exposure levels, possible only in laboratory animal studies, produce harmful effects. Due to its rapid metabolism and elimination, NP does not pose a risk at lower, more realistic exposure levels.

The laboratory animal studies demonstrate that oral doses of NP are rapidly absorbed, metabolized and excreted so that there is no significant accumulation of NP in any body organ or tissue. Free NP is only found following exposure at very high doses — above 10 milligrams per kilogram body weight per day (10 mg/kg/d) — doses thousands of times higher than worst-case estimates of human exposure to NP from products made with TNPP and NPE.

Furthermore, these studies indicate that NP and other alkylphenols (APs) — even at doses many times higher than worst-case exposure estimates — are metabolized by the normal process in which the body attaches a water-soluble component (glucuronide) to a less water-soluble molecule, like an AP, to facilitate elimination from the body. These AP metabolites do not have estrogenic activity in a highly sensitive test for such activity.

These new findings are consistent with, and fully support, the results of a multi-generation study conducted by the US National Institute of Environmental Health Sciences (Chapin et al., 1999) that found no effects on reproduction or development from NP doses as high as 200 parts per million (ppm) in the diet (15 mg/kg/d), and no effects on fertility at doses of 2000 ppm in the diet (150 mg/kg/d).

At least for NP, new studies such as those called for by IPCS, are now available and these confirm the safety of NP.

Additional information is available on the Alkylphenols & Ethoxylates Research Council website, www.aperc.org.

 

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