Emily,
Thanks for your comments. Could you explain more what you mean by "environment or genes can impact health without the presence of the other"? I'm confused because all living beings have genes and all living occurs within an environmental context. Do you mean that environmental factors influence some outcomes in a similar way regardless of any genetic variation of the organism? And some genetic factors influence outcomes in a similar way regardless of any environmental context? That is no doubt true, although it is often surprising how environmental modifications can essentially eliminate adverse consequences of pretty serious genetic diseases, e..g, PKU, a genetic disease for which dietary modification dramatically reduces consequences.