PULLMAN, Wash. — In the United States about 10 million people are afflicted by severe multiple chemical sensitivity. Many MCS sufferers give up air travel, some must find new work places or move out of their homes to avoid exposure to certain chemicals. For them, grocery shopping in the detergent aisle or attending events where someone may wear perfume is risky. MCS symptoms, which may last for hours or days, include pain–severe headaches and pain in joints and muscles–fatigue, dizziness and an impaired ability to think clearly.

The onset of this chronic condition can usually be traced back to an exposure to certain chemicals. But why the initial exposure results in an often life-long, incurable condition has been a mystery. In an article published in the September 2002 issue of the prestigious publication of the Federation of American Societies of Experimental Biology, “The FASEB Journal,” Washington State University biochemist Martin Pall suggests that a vicious chemical cycle may be to blame.

Pall’s new theory is a fusion of two previous theories about MCS. One of these, proposed by Pall earlier, states that MCS is produced by excessive levels of two chemicals in the body–nitric oxide and its oxidant product – peroxynitrite. He suggested certain mechanisms act to keep levels of the two compounds elevated, thus producing chronic changes. The second theory was proposed by Iris Bell, M.D, Ph.D. of the University of Arizona. She proposed that the central mechanism in MCS is neural sensitization in the brain.

“What my article reports,” said Pall, “is that if you assume both previous theories are correct, you come up with a fusion that explains all the most puzzling features of MCS. It explains why MCS is induced by a previous chemical exposure and why MCS sufferers show such a high level of sensitivity to a wide range of organic chemicals.”

Pall cites many studies that suggest that the initial chemical exposure creates a hypersensitivity in the neurons in the brain, which react by creating the two chemicals that cause further hypersensitivity. “Ordinarily, these activities are highly regulated, acting only on specific synapses in the brain where they are involved in learning and memory. The MCS response is produced,” said Pall, “when chemical exposure produces excessive responses over large regions of the brain. In this way, normal and important mechanisms may act to generate this chronic illness. Thus, not only is the brain constantly inundated by chemicals to which it is normally somewhat sensitive, but the brain of a person suffering from MCS becomes abnormally sensitive to the chemicals–from 100 to 1,000 times more sensitive than in an unaffected person.” Two other mechanisms contribute to the sensitivity to by allowing the offending chemicals to accumulate to higher levels in the brains of MCS people.

MCS has overlaps with other medical conditions of uncertain mechanism including chronic fatigue syndrome, fibromyalgia posttraumatic stress disorder, and Gulf War syndrome. Pall has proposed similar mechanisms for all of these conditions. “The notion that a biochemical vicious cycle may underlie all four is very exciting and, if correct, suggests that this is a major new paradigm of human disease.”

Interrupting this cycle may be the key to effective MCS treatment, said Pall.

Pall’s article is available on the Web at www.fasebj.org/cgi/content-nw/full/16/11/1407/T1. Access to this site is free to members of the Federation of American Societies of Experimental Biology, others must pay a $7 access fee.

Dr. Gunnar Heuser, neurotoxicologist and clinical professor at UCLA, who has published on brain changes in Chronic Fatigue Syndrome, stated “I consider Dr. Pall’s research a significant contribution to the science of clinical toxicology and multiple chemical sensitivity.”

Dr. Grace Ziem, Maryland physician who practices occupational and environmental medicine and specializes in chemically-induced illness, said “I feel that Dr. Pall has done the most important biochemical research and documentation toward understanding the mechanism of neural sensitization underlying toxic injury to the brain and this research has important implications for treatment.”