December 11, 2000

ALKYLPHENOLS BULLETIN
LITTLE EVIDENCE OF LOW-DOSE EFFECTS FROM NONYLPHENOL

A recent peer-review panel of scientists convened by the US National Toxicology Program (NTP) explored the potential for endocrine toxicity to be caused by low level or "low-dose" exposures to chemicals. Their review included unpublished data on nonylphenol conducted by the Food and Drug Administration's National Center for Toxicological Research (NCTR) in Jefferson, Arkansas, as well data published in peer-reviewed journals.

According to observers of the peer-review process, the panelists were unable to define what exactly constitutes a low dose. For example, in the case of nonylphenol, the doses considered "low" exceeded estimated human exposure levels by at least 5,000 times.

The preliminary conclusions reached by the panel, released at the end of the workshop on October 12, indicated that the low-dose effect observed in the NCTR research on nonylphenol was a non-standard immune endpoint added to the standard battery of immunotoxicity assays.

During the workshop, Dr. Kimber White, who led the research team at the Virginia Commonwealth University on behalf of NCTR, pointed out that nonylphenol did not alter any generally recognized immune functions at the lowest dose levels. He further indicated that there was no scientific way to evaluate the other effects seen since they were observed in a wide range of test materials. He further stated that it was premature to conclude the effects are evidence of low-dose toxicity.

The low-dose theory, advanced recently by some researchers, hypothesizes that a variety of biological effects might occur from very low exposures to compounds even when no effects are seen at the higher exposure levels normally tested. In its review of a number of compounds, including industrial chemicals and natural plant hormones, the NTP panel found the evidence for the low-dose theory to be inconclusive for nonylphenol and recommended further research.

The NTP panel's recommendations for further research included clarifying the significance to human health of the immune effects observed in the unusual NCTR assays. Robert Fensterheim, Executive Director of the Alkylphenols & Ethoxylates Research Council, said that it would be inappropriate and premature to base any public health or regulatory decisions on these observations without additional research.

"The weight of the scientific evidence continues to support the safety of nonylphenol and its derivatives," said Fensterheim, "When used and disposed of properly, these compounds pose no significant risk to the environment or human health."

Nonylphenol is used primarily to make nonylphenol ethoxylates, employed as cleaning agents and other high-value products in a wide range of industries. Nonylphenol derivatives are also used as additives in certain plastics and personal care products.                                                                                                                              

 

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