Dr. Nicholas Ashford, my co-author of the book Chemical Exposures: Low Levels and High Stakes, presented a thought-provoking analogy about how the same chemical exposure can affect people differently. His comments came at a National Academy of Sciences workshop in April 2012. I presented at the same workshop on TILT, or Toxicant-induced Loss of Tolerance; the QEESI, or Quick Environmental Exposure and Sensitivity Inventory; and the need for EMUs, or environmental medical units.

Here are Dr. Ashford’s remarks:

“Let me ask you to do a thought experiment. Suppose there were 10 Apple computers lined up along that front table and I were to open the motherboards of all those computers. Now suppose I were to take 10 pairs of those little Scottie magnets that your kids play with and I threw a pair of magnets into the motherboards of all 10 computers and then closed the computers and asked the first computer to add 2 and 2 and it gives me ‘minus 5.’ Then I asked the second computer how much is 2 and 2 and it says, ‘Well over 3.’ The third one just whirs. The fourth one doesn’t do anything, and so on, for each computer, down the line.

“Now if we had computer epidemiologists they would look at these 10 computers and they’d say they are all sick and each appears to have a different disease, i.e., each gives a different wrong answer to the question how much is 2 plus 2. If the epidemiologists didn’t see me throw the Scottie magnets into the computer, they would say these are unrelated diseases. Not only that, but the incidence of the malfunction — each rendition of a wrong, but different answer to the question how much is 2 plus 2 — would not be significant enough to say there was any disease in the population at all because not enough of the computers gave the same wrong answer. That’s what we’ve got with brain-mediated, brain-damage disease and I would argue that one of the bases for Toxicant-induced Loss of Tolerance is brain-mediated damage.

“When you throw a neurotoxic chemical into the brain, and you know a lot of them get into the brain, including the limbic system, which is where the immune system, the nervous system, and endocrine system converge, they may make the brain misbehave in a number of different ways. One of the ways in which it may misbehave may be endocrine disruption. Another way that it may misbehave is attention deficit hyperactivity disorder (ADHD). A third way in which it may misbehave is that autism can develop.

“Now I said it was a thought experiment, but probably the organ we know the least about and which is computer central to our entire existence is our brain. Toxicant-induced Loss of Tolerance can manifest in a number of seemingly unrelated ways, unexplained by classical toxicology that assumes a one-hit or single insult resulting in a single kind of pathology.”

I presented April 18 at the National Academy of Sciences Workshop “Biological Factors that Underlie Individual Susceptibility to Environmental Stressors and Their Implications for Decision-Making.”

The proceedings are available by recorded webcast so you can view and listen to the speakers. View the webcast at:

http://www.tvworldwide.com/events/nrc/120418/
(Supply your email adress to log in.)

The title of my presentation was “Human Variability in Chemical Susceptibility (Intolerance/Sensitivity): Research Findings to Date and Their Implications for Future Study Design.” I’ve posted my presentation for your review.

I was asked to describe our findings from the QEESI, the Quick Environmental Exposure and Sensitivity Inventory, and to discuss the use of EMUs, environmentally-controlled medical units, for research. Here is a synopsis:

“The QEESI is a validated research tool widely used to identify and characterize chemically intolerant individuals and groups. Results from these studies provide evidence for broad endogenous variability in susceptibility and point to the complex nature of susceptibility in humans, with susceptible persons generally reporting adverse responses to chemically diverse substances, including foods and drugs. Future investigations to assess human variability that is ‘endogenous or biological’ will benefit from the use of EMUs. Such studies will enable us to correlate symptoms and clinical measures (such as pulmonary function and EEG measures) with changes in the ‘-omics’ in real time at key points, i.e., when subjects enter the EMU, once they have achieved a clean baseline, and pre- and post- low level challenges.”

The QEESI is available free for download.

Details about the workshop are at:
http://nas-sites.org/emergingscience/workshops/individual-variability/