There are also researchers who say that mild smokers (one to five cigarettes per day) who also carry the CYP1A1 Val allele have increased risk of breast cancer. This shows the interaction between genetic inheritance and the environment.
也有研究者指出，輕微抽煙者（每日 1 ∼ 5 根）若帶有名為「CYP1A1 Val」的對偶基因，會增加罹患乳癌的危險性，可見基因與環境的交互影響。