A survey of industry indicated thiodipropionic acid and dilauryl thiodipropionate were not added to processed foods in 1970. There might be some quantity of these compounds in antioxidant formulations in use today that the Select Committee has not been able to identify. If so, it is most likely to be small. In any case, it may be advisable that this value be ascertained. These substances are of limited value as antioxidants in food systems but may be of greater importance in food packaging films. If thiodipropionic acid and dilauryl thiodipropionate are added to food, present limitations require that the total content of antioxidants may not exceed 0.02 percent of fat or oil content, including essential (volatile) oil content of the food. When used in food packaging, the resulting level of addition to the packaged food must be less than 0.005 percent.
Thiodipropionic acid and dilauryl thiodipropionate are of low acute toxicity when orally administered to experimental animals. Doses of 100 mg per kg administered to rats were absorbed and largely excreted in the urine within a few days as thiodipropionic acid or an acid labile-conjugate. Apparently less than 10 percent is otherwise metabolized, and in the case of the ester, evidence of some incorporation into fat depots was detected. No studies of the disposition of these compounds in humans or subhuman primates are available for review. Test of the teratogenic and mutagenic effects of both compounds did not suggest cause for concern. The only reports of feeding studies are unpublished and of limited thoroughness. The unpublished feeding studies on thiodipropionic acid in rats and guinea pigs presented no adverse effects as measured by growth rate or mortality. However, in unpublished long term studies, the investigators noted increased mortality in groups of rats fed dilauryl thiodipropionate as 0.5 and 3 percent of the diet and as a mixture with thiodipropionic acid as 1.1 percent of the diet. It would seem advisable to conduct adequate long term feeding studies on thiodipropionic acid and dilauryl thiodipropionate should it be ascertained that significant amounts are currently being used.
In light of these considerations, the Select Commitee concludes that: There is no evidence in the available information on thiodipropionic acid and dilauryl thiodipropionate that demonstrates, or suggests reasonable grounds to suspect, a hazard to the public when they are used at levels that are now current and in the manner now practiced. However, it is not possible to determine, without additional data, whether a significant increase in consumption would constitute a dietary hazard. There is no evidence in the available information on thiodipropionic acid and dilauryl thiodipropionate that demonstrates or suggests reasonable grounds to suspect a hazard to the public when they are used as ingredients in food packaging materials at levels that are now current or that might reasonably be expected in the future.