This is a survey for persistent, bioaccumulative, and toxic (PBT) pollutants in the U.S. milk supply. The EPA Environmental Radiation Ambient Monitoring System (ERAMS) was used to collect two sets of milk samples, one set in July 2000 and the second in January 2001. ERAMS has about 50 milk sampling stations located within the major population centers of 41 U.S. states, Panama, and Puerto Rico. It is estimated that the ERAMS milk samples represent roughly 20% of the U.S. milk supply. A portion of the samples will be used to create composites, which will be analyzed for approximately 30 PBTs. In addition, each individual milk sample will be analyzed for five PBT chemicals determined to be of the most concern. As an adjunct to this project, a separate document is being developed which provides environmental summaries on selected PBT's, including: chemical and physical properties; production, use, and disposal information; U.S. and international regulatory status; environmental fate and transport; monitored environmental media levels; and human toxicity and exposure information.

Cow's milk was selected for this survey for several reasons. About half of the animal fat ingested by Americans is from some form of dairy product, and EPA estimates that, for dioxins, one-third of an adult's total daily intake comes from dairy products. Children are estimated to have higher percentages. Like dioxin, the other PBT pollutants are likely to be widely dispersed in the environment, bioaccumulated through the food chain and ultimately result in low level contamination in most animal fats. Since milk fat may be one of the highest dietary sources of exposure to PBTs, it is important to understand their levels in this food. A second reason to study milk is that it offers the opportunity to examine geographic variability. Other animal fats are nationally distributed and difficult to trace back to a specific region. Milk, however, is produced and distributed on a regional scale. Understanding regional variability may offer clues to sources which release these compounds and processes by which they enter our food supply.