The study I am aware of shows that the hypervariable regions are effected by chemicals such as acetaldehyde but the differences in mutations rates compared with the control segments is not statistically significant - the researchers have stated that this may be the result of the technique they use.Kind RegardsNeil McGregorBDS, MDSc, PhDPhone: 61 3 95721570Email 1: neil.mcgregor1@bigpond.comEmail 2