Illness from low levels of environmental chemicals: relevance to Chronic Fatigue Syndrome (CFS)

Source – AJM 1998 Sep 28;105(3A):74S-82S

This article summarizes (1) epidemiologic and clinical data on
the symptoms of maladies in association with low-level
chemicals in the environment, i.e., environmental chemical
intolerance (CI), as it may relate to chronic fatigue syndrome
(CFS) and fibromyalgia; and (2) the olfactory-limbic neural
sensitization model for CI, a neurobehavioral synthesis of
basic and clinical research.

Severe CI is a characteristic of 20-47% of individuals with apparent
CFS and/or fibromyalgia, all patients with multiple chemical sensitivity
(MCS), and approximately 4- 6% of the general population. In the
general population, 15-30% report at least minor problems with CI.
The levels of chemicals reported to trigger CI would normally be
considered nontoxic or subtoxic. However, host factors–e.g.,
individual differences in susceptibility to neurohormonal
sensitization (amplification) of endogenous responses– may
contribute to generating a disabling intensity to the
resultant multisystem dysfunctions in CI. One site for this
amplification may be the limbic system of the brain, which
receives input from the olfactory pathways and sends efferents
to the hypothalamus and the mesolimbic dopaminergic [reward]
pathway. Chemical, biologic, and psychological stimuli can
initiate and elicit sensitization. In turn, subsequent
activation of the sensitized limbic and mesolimbic pathways
can then facilitate dysregulation of behavioral, autonomic,
endocrine, and immune system functions.

Research to date has demonstrated the initiation of neurobehavioral
sensitizationby volatile organic compounds and pesticides in animals,
as well as sensitizability of cardiovascular parameters,
beta-endorphin levels, resting EEG alpha- wave activity, and
divided-attention task performance in persons with CI. The
ability of multiple types of widely divergent stimuli to
initiate and elicit sensitization offers a new perspective on
the search for mechanisms of illness in CFS and fibromyalgia
with CI.

Bell IR, Baldwin CM, Schwartz GE

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