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From the National Institute of Health:

NTP 1998 Annual Plan -- Carcinogenesis

Chapter VIII CARCINOGENESIS:

Ethoxyquin:
Ethoxyquin is used as an antioxidant preservative in animal feed and dehydrated forage crops, as an antiscald agent in pears and apples, and as a color preservative in spices. Toxicity studies of ethoxyquin were conducted because of increased use and high levels of ethoxyquin (150 ppm) in animal feeds, and potential human exposure. Ethoxyquin is known to induce kidney damage in rats. Fourteen-day and 90-day dosed feed toxicity studies in rats and mice have been completed. (CONTACT PERSON: Dr. P. Chan, ETP, NIEHS)

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H&S:ETHOXYQUIN 91-53-2

*SAX TOXICITY EVALUATION: THR: Poison by intraperitoneal route. Moderately toxic by ingestion. Mutagenic data.

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From the FDA:

August 14, 1997 FDA REQUESTS THAT ETHOXYQUIN LEVELS BE REDUCED IN DOG FOODS

In letters dated July 31, 1997, to manufacturers of ethoxyquin and trade associations for the pet food industry, FDA's Center for Veterinary Medicine (CVM) requested that the maximum level for ethoxyquin in complete dog foods be voluntarily lowered to 75 parts per million (ppm). Under the current food additive regulations, ethoxyquin is allowed at levels up to 150 ppm in complete dog foods (Title 21, Part 573.380 of the Code of Federal Regulations). However, after recently completing a scientific review of a voluntarily-submitted study from the Monsanto company, CVM has reason to believe that the 150 ppm level may not provide an adequate margin of safety in lactating female dogs and possibly puppies.

The results from this study show that ethoxyquin levels above the current tolerance in dog foods produced no adverse reproductive effects. There was, however, an increase in a dark, reddish-brown pigment in the liver of female dogs immediately after completing a 6-week lactation. The liver pigment was identified as protoporphyrin IX, a normal intermediate in the synthesis of heme. This pigment was also associated with elevations in liver-related enzymes in the serum of a few animals. During lactation, the female dogs consumed two to three times more food as a percentage of body weight than they did at maintenance, and this increased food consumption likely contributed to the increased pigment deposition in the liver and in the elevated serum enzymes. The increased pigment deposition and serum enzymes in lactating female dogs may be reversible when food consumption returns to maintenance, but it still constitutes a finding that must be further investigated.

The Pet Food Institute has undertaken a study designed to show that ethoxyquin is an effective antioxidant at levels between 30 and 60 ppm in a complete dog food. FDA is closely monitoring the progress of this study. If new information becomes available that questions the safety of ethoxyquin at 75 ppm in dog food, or shows it to be an effective antioxidant at levels below 75 ppm, CVM will consider further action.

Further information on this subject is available from FDA/CVM's Division of Animal Feeds, 7500 Standish Place, HFV-220, Rockville, MD 20855 or by calling (301) 594-1724.

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