Trends in the levels of N-nitrosodimethylamine in Canadian and imported beers

N-Nitrosodimethylamine (NDMA) is a potent animal carcinogen that has been detected in trace levels in beers. Studies carried out by the Canadian Health Protection Branch suggest that as a result of improvement in the malt-drying techniques, NDMA levels in both Canadian and imported beers have decreased significantly over the past 10-15 years. Of 162 Canadian beers analyzed during 1982-1989, the average NDMA level was found to be 0.098 ppb (range, <0.1-0.6 ppb) as compared to average levels of 1.4 and 0.7 ppb detected in two earlier (1978 and 1980, respectively) surveys. In the two latest surveys of imported beers carried out during 1991-1992 and 1994, the respective averages were 0.71 ppb (n = 106 ; range, <0.1-9.1 ppb) and 0.15 ppb (n = 36 ; range, <0.1-3.2 ppb). The current daily intake of NDMA through beer by an average Canadian is about one-fifteenth of that estimated in 1978-1980.