Alar in Fruit: Limited Regulatory Action in the Face of Uncertain Risks

Abstract

1, 1-Dimethylhydrazine (UDMH) is a breakdown product of daminozide (tradename “Alar”), a plant growth regulator which was used on fruit, most notably apples. The carcinogenic activity of UDMH was first reported in 1967 when lung tumors were noted in UDMH-exposed mice, and then was confirmed in the early 1970s when both lung tumors and hemangiosarcomas were observed in mice. These early findings were again confirmed; hemangiosarcomas in hamsters and lung adenomas in rats were also observed. Because the early studies did not follow good laboratory practice procedures instituted in 1979, the early results were discounted, particularly for quantitative risk estimation, and regulation of daminozide as a carcinogen delayed. In 1987, the EPA published a cancer potency value for UDMH derived from the early mouse study. Using this potency estimate, the Natural Resources Defense Council (NRDC) predicted that average risks to preschoolers from daminozide use approached 1/1000, and widely publicized this finding as unacceptable. As a consequence, apples were soon removed from the luncheon menus of elementary schools and the public voiced general skepticism about the safety of the food supply. In response, EPA, various state agencies and other groups developed their own risk estimates. We discuss the EPA and NRDC assessments and the basis for the differences in their risk estimates, including assumptions concerning risks from early-in-life exposure, the fraction of UDMH derived from daminozide, appropriate subpopulations, representative parameters of the potency distribution, and corrections for bioassay length. It is demonstrated that some plausible estimates of risk, derived from conservative, reasonable assumptions, exceed those developed by EPA and NRDC.