Environmental toxins, the endocrine disrupting hypothesis in aging people
In the eponym Soap opera, House M.D. ordered his team to test their patient for heavy metal poisoning, organophosphate poisoning, biological toxins and to do an environmental scan of the patient's home.
Is there any scientific reality in this fiction? Are we exposed to environmental toxins in our everyday life? Why are aging people more at risk?
Exposure to environmental toxins is a lifetime issue and affects particularly older adults
Older adults' bodies contain a lifetime's worth of environmental contaminants, many of which can remain in their systems for decades. Elderly people are highly vulnerable to these toxins, because their brain has a reduced capacity to compensate for impairment, and because they have been longer exposed than younger adults. For example, elders were exposed to much higher lead concentrations given that gasoline contained lead (which is not the case anymore since 10-30 years). This is what we call, a cohort effect. In the Third National Health and Nutrition Examination Survey, blood lead measurements were obtained from 13 642 U.S. individuals of all ages. One of the most striking results was that older people (above 50 years of age) had the highest lead level in their blood sample. Regarding organic pollutants, although the production of polychlorinated biphenyls (PCBs) stopped in 1977, large numbers of electrical capacitors and transformers, still in use, contain PCBs. Leaks from capacitors and transformers and poor handling of wastes in production facilities have led to widespread dispersion of PCBs into the environment. PCBs persist in the environment and in the fatty tissues of humans. Many residents of our countries have detectable PCBs in their blood, particularly older Americans.
Is there a possible link between environmental toxin exposition and cognitive deficits?
History is often source of knowledge. In Taiwan, approximately 2 000 people were accidentally exposed to PCBs due to ingestion of contaminated cooking oil in 1979. Twenty-five years later, a study showed elderly women exposed to these PCB had attention and memory deficits. Numerous studies have documented this effect in people exposed through their job, for example in vineyard workers exposed to pesticides, in workers from ferroalloy plants or welders exposed to manganese. Even in the general population, associations have been found between exposure to toxins and measures of attention in several populations of older adults.
How environmental toxins may impair our brain?
The secret of environmental toxins is that they are able to imitate some messengers of our body: the hormones. That’s the reason why many people call them « endocrine disrupting chemicals ». For example, estrogen is the main female sex hormone and many environmental estrogens and anti-estrogens have been identified among pesticides (DDT, Dieldrin, Organophosphates), herbicides (Atrazine), heavy metals (lead, cadmium), industrial chemicals (PCBs, dioxins and furans) and plasticizers (Bisphenol A, surfactant). More recently, studies have shown that heavy metals may target the stress hormones. The role of the stress hormones in cognitive performance during human aging has been well documented by scientists and the stress system could be the key explaining how environmental toxins may impact our brain.
What is the good news?
The good news in this little story is that exposure to environmental toxins is a preventable factor. Based on scientific evidences, governments are working to ban the most dangerous toxins from our everyday life. For example, we have lead free gas today! Bisphenol A, which was banned in October 2008 by Canada, is also a good example of these kind of actions. Because many toxins are in products we buy, everyone can play a role in this prevention. Here are a couple of actions that you can take to reduce environmental toxins from your environment:
- Choose more carefully food with limited pesticides
- Opt for renovation materials that are less dangerous for the environment
- Use batteries without mercury