OCCURRENCE OF ETHYL CARBAMATE (URETHANE) IN UNITED-STATES AND CANADIAN BREADS - MEASUREMENTS BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

In a survey of U.S. and Canadian breads, urethane, a chemical shown to be carcinogenic in animals, was detected at low levels in 22 batches of commercial breads and rolls that were sampled immediately after bak ing. The mean level of urethane was 2.06 +/- 0.2 ppb for measurements on composite samples of 12 loaves prepared using established procedure s for trace nutrient analysis. The mean value of urethane was less tha n one third the 7-ppb value used by others to estimate probable nonalc ohol human dietary exposure to urethane. Based on the newly determined mean level for urethane and bread consumption data, the per capita di etary intake per year in the United States is 47 +/- 4 mug for untoast ed bread. Chemically specific gas-chromatographic detectors employing either high-resolution mass spectrometry or methane chemical-ionizatio n mass spectrometry were used for all measurements, yielding a quantif ication precision of +/- 0.2 ppb at the l-ppb level. The average recov ery of urethane from white bread was 110% in the 3-7 ppb range.