Denatonium saccharide is the most bitter substances known, judged to be 5 times more bitter than denatonium benzoate. Detectable at as little as a few parts per billion, this compound will make a product so bitter that children and pets will not be able to swallow it. Denatonium saccharide makes sweet but highly toxic products such as antifreeze and detergents taste foul. Research shows that people can detect denatonium saccharide in water at 50 parts per billion. Denatonium saccharide is bitter at 1 to 10 ppm, at 30 to 100 ppm virtually any product becomes impossible to masticate. Denatonium saccharide is also stable and inert. In addition, so little is needed that the properties of the product remain unchanged.

The EPA has determined that denatonium saccharide is generally safe. Here is EPA’s 2014 interim decision:

Epa denatonium saccharide interim decision

Denatonium saccharide is a bittering agent in squirrel, vole, dog, and cat repellents used on outdoor surfaces and structures such as trees, fences, poles, decks, planters, siding, garbage cans, furniture, seeds, and bulbs.

EPA conducted a qualitative human health risk assessment and did not identify any risks of concern. The ecological risk assessment identified potential risks for birds and listed mammals. However, due to the number of conservative assumptions included in the assessment, there are no labeling changes at this time. The risk assessment for denatonium saccharide did not come to a conclusion of “no effect” to listed species. Therefore, consultation with the U.S. Fish and Wildlife Service (USFWS) on the potential risk of denatonium saccharide to listed species will be necessary.

Denatonium saccharide has not been evaluated under the EDSP. Therefore, the Agency’s final registration review decision is dependent upon the result of Section 7 Endangered Species consultation with the USFWS and the evaluation of potential endocrine disruptor risk.