Phone: 202.419.1506
Fax: 202.659.8037
or: info@aperc.org
NEWS
FOR IMMEDIATE RELEASE
September 10, 1999
Octyphenol Study Finds No Reproductive or Estrogenic Effects
Findings Add to Growing Evidence of Lack of "Low Dose" Effects
A new study has found no adverse effects on the reproductive system of laboratory rats from exposure to octylphenol (OP), casting further doubt on previous studies reporting effects from low doses of chemicals.
The study, "Two-Generation Reproduction Study with p-tert-Octylphenol (OP) in Rats", also did not show endocrine-related effects from OP. The study design is considered the definitive evaluation for effects on mammalian reproduction by government agencies and scientists throughout the world.
The researchers, led by Dr. R.W. Tyl of Research Triangle Institute, conclude that "no estrogenic or reproductive effects occurred from dietary exposure to rats for two generations over a 10,000 fold dose range." They found no effects on any reproductive parameters and no effects on sperm measurements, estrous cycling or reproductive organs at dietary concentrations of 0, 0.2, 20, 200 and 2000 ppm (parts per million) of OP.
The researchers note that OP has been "implicated as an environmental estrogen due to its weak binding to the estrogen receptor" and that they conducted the study to "determine if OP presents a risk to [human] reproductive health." The results of the study indicate that OP would not be considered an "endocrine disrupter" in mammalian systems, using the internationally accepted definition of the term (Weybridge Conference).
Based on their findings, researchers established the No Observed Adverse Effect Level (NOAEL) for reproductive toxicity at greater than 150 milligrams of OP per kilogram of body weight per day and for general toxicity at approximately 15 mg/kg/day. Because potential human exposure to OP is generally estimated to be less than 0.001 mg/kg/day, many times lower than these NAOELs, it does not appear that the use of OP poses a significant risk to humans.
The study casts serious doubt on the results of some previous studies on OP and on the theory that current toxicity testing is inadequate to address effects from low doses of endocrine active chemicals.
The researchers conclude that the study did not support preliminary reports of effects on sperm count and testes weights from low doses of OP. In 1995, Dr. Richard Sharpe and colleagues reported effects on the reproductive system of male laboratory animals exposed to octylphenol and other chemicals. However, efforts to repeat the findings by others have not been successful, and Sharpe and colleagues reported last year that they were unable to reproduce key results of that study, including those with OP. The results of this preliminary study have been frequently cited in support of the endocrine disrupter theory.
In 1998 Dr. Frederick S. vom Saal, a researcher at the University of Missouri-Columbia, reported decreased sperm production from exposure to low doses of OP in a limited study in mice. The new study reported today, which followed U.S. EPA OPPTS Guidelines and looked at two generations of a much larger number of rats over a wide range of doses, is considered definitive and raises serious questions about the validity of the mouse study.
The study results will be published in an article in an upcoming edition of Regulatory Toxicology and Pharmacology. The results also were reported at a recent Society of Toxicologists (SOT) meeting in Washington, D.C.
OP is used primarily to make octylphenol ethoxylate (OPE) surfactants, a class of alkylphenol ethoxylate (APE) compounds. OPEs are used in cleaning products and in pulp and paper, textiles, coatings and other industrial processes.
 |