Multiple chemical sensitivity triggers

What has become an even greater concern in recent years is the phenomenon known as multiple chemical sensitivity disorder triggered by exposures to many chemicals in the environment. Synthetic chemicals are all around us. They are in the products we use, in the clothes we wear, in the food we eat, in the air we breathe at work. Because chemicals are everywhere in the environment, it is not possible to escape exposure. For this reason many people have become sensitized to the chemicals around them. In fact, it is estimated that 15% of the population has become sensitized to common household and commercial products. For some people the sensitization is not too serious a problem. They may have what appears to be a minor allergy to one or more chemicals. Other people are much more seriously affected. They may feel tired all the time, and suffer from mental confusion, breathing problems, sore muscles, and a weakened immune system. Such people suffer from a condition known as Multiple Chemical Sensitivity (MCS). 

Multiple chemical sensitivity (MCS) or multiple chemical intolerance (MCI) is a term used to describe a variety of symptoms associated, in some cases, with exposure to indoor air contaminants. Individuals with this syndrome seem to respond to very low levels of chemicals, and the condition can involve various organ systems. It appears to be induced by a wide variety of agents, but once induced it can be triggered by low-concentration exposures to numerous other chemicals. Indoor air pollutants not only appear to set off symptoms in the chemically intolerant, but several studies suggest that some pollutants or pollutant mixtures may also initiate the condition. This phenomenon has been described in... 

In many cases, multiple chemical sensitivity symptoms result from classical conditioning. An initial exposure causes emotional reactions during or after the exposure odor acts as a future trigger or conditioned stimulus for symptoms. Symptoms result from autonomic hyperactivity from fear of exposure (Amundsen et al. 1996 Bolla-Wilson et al. 1988 Schottenfeld 1987 Shusterman and Dager 1991). 

Since a majority of toxic chemicals trigger multiple adverse effects, it is important to understand the spectrum of effects. Such data on chemical(s) help to evaluate the chemical safety and/or health risks posed to humans. Simultaneous exposure to multiple chemicals makes the problem more complex. All these aspects suggest a plethora of toxic effects of chemical combinations. Further, as seen in the acute toxicity profile of pesticides on bird species, the genetic diversity of animal species and humans underlines the role of individual sensitivities on the induction of toxic effects of chemicals. 

The olfactory epithelium is composed of basal, neuronal (olfactory), and susten-tacular (support) cells (Figure 27.3). The portion of each olfactory cell that responds to the olfactory chemical stimuli is the cilia. The odorant substance first diffuses into the mucus that covers the cilia and then binds to specific receptor proteins in the membrane of each cilium. Next, receptor activation by the odorant activates a multiple molecules of the G-protein complex in the olfactory epithelial cell. This, in turn, activates adenylyl cyclase inside the olfactory cell membrane, which, in turn, causes formation of a greater multitude of cAMP molecules. Finally, the cAMP molecules trigger the opening of yet an even greater multitude of sodium ion channels. This amplification mechanism accounts for the exquisite sensitivity of the olfactory neurons to extremely small amounts of odorant. The olfactory epithelium is an important target of certain inhaled toxicants. Certain metals, solvents, proteins, and viruses are transported to the brain via transport from the olfactory epithelium to the olfactory tract and exert neurotoxicity. 

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