Azodicarbonamide (ADC) has long been used by commercial bakers to strengthen dough, but has been poorly tested. A 1999 review published by several United Nations agencies concluded that "There are no adequate data relating to carcinogenic, reproductive, or developmental effects, hence it is not possible to evaluate the risk to human health for these endpoints."

Most of the concern about ADC relates to two suspicious chemicals that form when bread is baked. The first chemical is semicarbazide (SEM), which caused cancers of the lung and blood vessels in mice. It did not cause cancer in rats. In 1976 the International Agency for Research on Cancer considered SEM to be a carcinogen in mice, but in 1987 concluded that the animal data were "limited" and that SEM was "not classifiable" as to its carcinogenicity to humans.

A second breakdown product, urethane, is a recognized carcinogen. ADC used at its maximum allowable level (45 ppm in bread) leads to levels of urethane in bread that pose a small risk to humans. Toasting that bread increases the amount of urethane. However, when used at 20 ppm, which may be the amount used by some commercial bakeries, a 1997 FDA study found "only a slight increase" in urethane. (Some urethane forms in bread not made with azodicarbonamide.)

Considering that many breads don't contain azodicarbonamide and that its use slightly increases exposure to a carcinogen, this is hardly a chemical that we need in our food supply. It appears that the Delaney amendment, which bars the use of additives that cause cancer in humans or animals, would require FDA to bar its use. At the very least, FDA should reduce the amount allowed to be used.