Hewer T, Rose E, Ghadirian P, Castegnaro M, Malaveille C, Bartsch H, Day N
Lancet. 1978 Sep 2;2(8088):494-6. doi: 10.1016/s0140-6736(78)92218-3.
Substances which are commonly sucked or chewed in two areas where the incidence of oesophageal cancer is high, the Transkei and north-east Iran, were tested in bacterial mutagenicity assays. Pyrolysed substances, opium dross in north-east Iran and tobacco pipe residues in the Transkei, displayed mutagenic activity in Salmonella typhimurium strains TA98 and TA100 in the presence of rat liver microsomes.