Commentary – The Toxic Legacies Within Us

We live in a soup of environmental pollution that has pervaded our tissues with a variety of toxic chemicals. Long-lasting lipophilic compounds have concentrated in our fat and heavy metals in our bones, and these chemicals have been locked away there for decades.

As we age, we metabolize fat and demineralize bone, and these reservoirs of past exposures are released back into tissues throughout our bodies, including the brain.  What are the impacts of these internal re-exposures late in life when imposed on the aging process? Neurotoxicity of early life exposures to heavy metals like lead and long-lasting lipophilic compounds such as PCBs entering the body have been widely studied, but the late life impacts of these chemicals exiting from internal stores has been relatively neglected.

The brain is not the only point of concern, other organs such as the kidneys should also be studied. Neurobehavioral problems such as cognitive deficits, sensory and motor impairment, as well as emotional dysfunction are not the only physiological processes of concern either. Increases in cancer, cardiovascular disease and diabetes should be evaluated too.

The toxic chemicals still within us can produce ongoing adverse health effects, but there are also continuing legacies of more mobile toxicants, like organophosphate pesticides.  The effects of these can be amplified due to aging-induced physiological decline and decreased resilience of older people. We can better respond and ameliorate the impacts of these toxic legacies by developing a clearer understanding of how our bodies are a part of the environment with reservoirs of toxicants and persisting toxic effects. Another benefit of considering our internal toxic legacies is the recognition not only of our role in contributing to the pollution, but also in any solutions. Hopefully, the neurotoxicity resulting from this internal toxic legacy within us does not compromise our brain function and impede our ability to adequately respond to the toxicity, or even to care about it in the first place.

By Edward D. Levin, Ph.D., Duke University