Figure 2. Historical levels of total tobacco-specific nitrosamines (TSNAs) (ppm) in American and Swedish moist snuff products, 1981–2002. Sources: Hoffmann and Adams, 1981; Österdahl and Slorach, 1984; Hoffmann et al., 1984, 1986, 1988, 1991, 1995; Brunnemann et al., 1985, 1987, 2002; Chamberlain et al., 1988; Djordjevic et al., 1989, 1993.