Americans have twice as much bisphenol-A (BPA) in their systems as Canadians, for reasons that are unclear, according to a new study. The study, published in the Canadian Medical Association Journal, said that the number of subjects in both countries with detectible BPA levels were similar, at more than 90%, but that the concentrations in the systems of the Americans was twice that of the Canadian subjects. BPA, a chemical used extensively in the linings of food and beverage cans, is controversial due to studies claiming that it mimics the effects of estrogen in the human body. The researcher who headed the study, Laura Vandenberg of Tufts University, said she didn’t have a firm explanation for the disparity between the U.S. and Canada, except that the U.S. has plants that produce BPA and Canada has none, leading to speculation of possible absorption through environmental contamination. Vandenberg also questioned the action of Health Canada in declaring BPA a “toxic substance” but failing to follow through with any recommendations for restricting its use.