New research shows that lead exposure might play a role in the mental decline of aging adults—even if that exposure took place years earlier. Researchers at Johns Hopkins University found past lead exposure can make an aging person’s brain operate as if it is five years older than its true age.

Scientists are discovering that exposure to a variety of pollutants may have a delayed effect on the body. The researchers say that earlier exposure to mercury and pesticides may have some of the same effects as lead. And past research has shown that exposure to pesticides may raise the risk of developing Parkinson’s disease more than a decade later.

Experts say that one of the biggest lead dangers may be your home; though lead-based paints have been barred in the U.S. since the late 1970s, many older homes still contain it. For more information on the harmful effects of lead—and how to rid it from your home—read “Choose Unleaded,” (Real Health, winter 2007).