Jet fuel, insect repellent and BPA and phthalates - chemical components of food containers and tooth fillings - have also been shown to induce a variety of heritable disorders in fourth-generation descendants, such as pubertal abnormalities and obesity. Though the chemical doses in these studies are much larger than one would typically receive from a contaminated environment, in the case of BPA, blood levels similar to those measured in pregnant American women induced changes in descendants out to the fifth generation which included spending less time exploring their environment.
And evidence on the effects of human exposure are not lacking. In 1976 an explosion at a chemical plant in Italy exposed residents to high concentrations of the industrial byproduct dioxin. In 2010 researchers reported that the exposure led to decreased fertility, a tendency to be overweight as well as thyroid abnormalities in subsequent generations. Thus, although shifts in lifestyle and food availability no doubt account for much of the increase in obesity, diabetes and other diseases of plenty over the past 50 years, it is conceivable that ancestral exposures to toxic chemicals have increased our susceptibility to such diseases.
Epigenetic effects play a crucial role in aging and cancer as well. And it is worth noting that epigenetic changes appear to occur 1,000 times more frequently than the classic mode of inheritance driven by mutations in DNA.
We can't always control our exposure to environmental pollutants present in air and water, but eating organic, shunning animal products (which concentrate chemicals in fat) and avoiding plastic containers are useful measures for minimizing contact with culprits.
Eating healthy and exercising could swing the epigenetic shift in your favor. If you increase your metabolic rate naturally by upping your lean body mass through plant foods and regular workouts, perhaps these habits will induce epigenetic changes for a fast metabolism that you then pass down to your child of the future. A trait we'd all like to be born with.
So remember, you are not just living cleanly for yourself. You are what you eat, but your kids and grandkids could be as well.