Multiple Chemical Sensitivity A 1999 Consensus ABSTRACT.
Consensus criteria for the definition of multiple chemical
sensitivity (MCS) were first identified in a 1989
multidisciplinary survey of 89 clinicians and researchers with
extensive experience in, but widely differing views of, MCS. A
decade later, their top 5 consensus criteria (i.e., defining
MCS as [1] a chronic condition
[2] with symptoms that recur reproducibly
[3] in response to low levels of exposure
[4] to multiple unrelated chemicals and
[5] improve or resolve when incitants are removed) are still
unrefuted in published literature.
Along with a 6th criterion that we now propose adding (i.e.,
requiring that symptoms occur in multiple organ systems),
these criteria are all commonly encompassed by research
definitions of MCS.
Nonetheless, their standardized use in clinical settings is
still lacking, long overdue, and greatly needed—especially in
light of government studies in the United States, United
Kingdom, and Canada that revealed 2–4 times as many cases of
chemical sensitivity among Gulf War veterans than undeployed
controls. In addition, state health department surveys of
civilians in New Mexico and California showed that 2–6%,
respectively, already had been diagnosed with MCS and that 16%
of the civilians reported an “unusual sensitivity” to common
everyday chemicals.
Given this high prevalence, as well as the 1994 consensus of
the American Lung Association, American Medical Association,
U.S. Environmental Protection Agency, and the U.S. Consumer
Product Safety Commission that “complaints [of MCS] should not
be dismissed as psychogenic, and a thorough workup is
essential,” we recommend that MCS be formally diagnosed—in
addition to any other disorders that may be present—in all
cases in which the 6 aforementioned consensus criteria are met
and no single other organic disorder (e.g., mastocytosis) can
account for all the signs and symptoms associated with
chemical exposure. The millions of civilians and tens of
thousands of Gulf War veterans who suffer from chemical
sensitivity should not be kept waiting any longer for a
standardized diagnosis while medical research continues to
investigate the etiology of their signs and symptoms.
AS RESEARCHERS AND CLINICIANS with experience in the study,
evaluation, diagnosis, and/or care of adults and children with
chemical sensitivity disorders, we support the stated goal of
the National Institutes of Health 1999 Atlanta Conference on
the Health Impact of Chemical Exposures During the Gulf War
“to fully characterize the nature of multiple chemical
exposures within the Gulf War veteran population and to relate
this characterization to what is known about Multiple Chemical
Sensitivity (MCS) and related conditions and disorders within
civilian populations.”(1) Based on research conducted by state
and federal government agencies, we already know that MCS is
one of the most commonly diagnosed chronic disorders in
civilians and the most common—but still largely
undiagnosed—disorder of any kind in Gulf War veterans of the
United States.
In statewide telephone surveys of randomly selected adults,
conducted by health departments in California in 1995 and 1996
and New Mexico in 1997, investigators found that 6% of adults
in California(2) and 2% of adults in New Mexico(3) indicated
that they had already been diagnosed with MCS or Environmental
Illness, whereas 16% in both states said they were “unusually
sensitive to everyday chemicals.” When randomly selected
adults in other states were asked if they were “especially
sensitive” (instead of “unusually” sensitive), one-third
consistently maintained that they were.(4–6)
Among Gulf War era veterans, data from the largest random
survey presented by the U.S. Department of Veterans’ Affairs
(VA) in 1998 (based on questionnaires completed by 11 216
deployed to the Gulf and 9 761 nondeployed) show that 5%
reported chemical sensitivity among the nondeployed personnel
and 15% reported the same among the deployed.(7) Other VA
researchers report much higher rates—but the same 3-fold
difference—in a smaller random sample of VA hospital
outpatients: 86% of ill veterans deployed to the Gulf
complained of chemical sensitivity, compared with 30% of
undeployed ill veterans.(8) In the only study in which MCS was
specifically assessed among veterans selected randomly from
the VA Registry, investigators found 36% of 1 004 met common
research criteria for MCS.(9) Among randomly selected
Department of Defense (DOD) personnel who remain on active
duty, two larger studies by the Centers for Disease Control
found slightly lower—but still significant—2.1- and 2.5-fold
increases in the prevalence of self-reported chemical
sensitivity among those deployed to the Gulf, compared with
those who were not deployed. In the “Iowa” study, in which the
prevalence rates for deployed and nondeployed individuals were
5.4% and 2.6%, respectively, investigators used a detailed
questionnaire to assess “probable MCS.”(10) In the
“Pennsylvania” study,(11) in which prevalence rates were 5%
versus 2%, respectively, only one “yes/no” question was asked
about chemical sensitivity. Canadian Gulf War veterans
reported only approximately one-half the prevalence of MCS
(2.4%), but nevertheless this was 4 times more than their
controls.(12) Even in the United Kingdom where MCS is little
known, Gulf War veterans report being diagnosed with MCS at
2.5 times the rate of military controls.(13)
Clearly, there is a significant need for a standardized
clinical definition of MCS and a comprehensive clinical
protocol that VA, DOD, and other physicians can use to
evaluate it. We recommend to our colleagues and the sponsors
of the Atlanta Conference—the Department of Health and Human
Services’ Office of Public Health and Science, the Centers for
Disease Control and Prevention, the National Institutes of
Health, and the Agency for Toxic Substances and Disease
Registry—that MCS be formally defined for clinical purposes by
the top 5 “consensus criteria” identified in a 1989 survey of
89 clinicians and researchers who had extensive experience in
MCS but who also held widely divergent views about its
etiology.(14) Included were 36 specialists in allergy, 23 in
occupational medicine, 20 in “clinical ecology,” and 10 in
internal medicine and otolaryngology. We would add only that
symptoms associated with chemical exposures must involve
multiple organ systems, thus distinguishing MCS from specific
single-organ system disorders (e.g., asthma, migraine) that
also may meet the first 5 criteria.
Consensus Criteria for MCS The following consensus criteria
for the diagnosis of MCS were gleaned from the study by
Nethercott et al.(14) (funded in part by grants from US NIOSH
and US NIEHS):
“The symptoms are reproducible with [repeated chemical]
exposure.” “The condition is chronic.” “Low levels of exposure
[lower than previously or commonly tolerated] result in
manifestations of the syndrome.” “The symptoms improve or
resolve when the incitants are removed.” “Responses occur to
multiple chemically unrelated substances.” [Added in 1999]:
Symptoms involve multiple organ systems.
Given the only other explicit consensus ever published on
MCS—the 1994 statement of the American Lung Association,
American Medical Association, U.S. Environmental Protection
Agency, and U.S. Consumer Product Safety Commission, that
“complaints [of MCS] should not be dismissed as psychogenic,
and a thorough workup is essential” (ALA 1994)—we recommend
that MCS be diagnosed whenever all 6 of the consensus criteria
are met, along with any other disorders that also may be
present, such as asthma, allergy, migraine, chronic fatigue
syndrome (CFS), and fibromyalgia (FM). MCS should be excluded
only if a single other multi-organ disorder can account for
both the entire spectrum of signs and symptoms and their
association with chemical exposures, such as mastocytosis or
porphyria, but not CFS or FM, which are not so associated.
To assist physicians who are unfamiliar with the evaluation of
MCS, we recommend that clinical protocols include validated
questionnaires for screening and characterizing chemical
sensitivity,(15,16) a list of overlapping disorders to
consider in the differential diagnosis of MCS, and a list of
signs and test abnormalities associated with MCS in the
peer-reviewed literature (summarized by Ashford and Miller(17)
and Donnay(18)). Although no single test is yet considered
diagnostic of MCS, those suggested by signs, symptoms, or
history may be helpful in treating and tracking the disorder.
The presentation of MCS may vary greatly among cases and over
time. Some individuals are totally disabled by severe symptoms
suffered on a daily basis, for example, whereas others are
disabled only minimally by mild symptoms suffered
occasionally. We, therefore, recommend that any clinical
diagnosis of MCS be characterized and followed over time using
quantitative and/or qualitative indices of life impact or
disability (e.g., minimal, partial, total); symptom severity
(e.g., mild, moderate, severe); symptom frequency (e.g.,
daily, weekly, monthly); and sensory involvement
(identification of which sensory pathways—olfactory,
trigeminal, gustatory, auditory, visual and/or touch,
including perception of vibration, pain and heat or cold—show
altered (+/–) sensitivity and/or tolerance for normal levels
of stimuli, either chronically or in response to particular
chemical exposures).
For research purposes that require greater homogeneity, we
encourage investigators to refine the consensus criteria for
MCS with whatever additional inclusion or exclusion criteria
they believe are needed to test their hypotheses. The indices
and domains that are used to characterize and select both
cases and controls in MCS research should be fully reported so
that results from different studies can be compared and their
broader applicability assessed.
Given the significant overlap in clinic populations of MCS
with both CFS and FM, as well as the need to better understand
the relationships between these disorders,(19–21) we recommend
that all “solicitations” and “requests for applications”
issued by federal agencies for human research into any one of
CFS, FM, or MCS direct investigators to screen for all three
(regardless of their selection criteria, which need not be
affected) and to report their results in these terms. There is
a precedent for this: the National Institute of Arthritis and
Musculoskeletal Disorders routinely requires that in studies
of fibromyalgia investigators must screen for and report any
overlap with temporo-mandibular joint disorder. CFS, FM, and
MCS research could all benefit from greater collaboration, and
so we welcome the Congressional initiative of Senator Tom
Harkin to earmark $3 million of the DOD’s 1999 Gulf War
illnesses research budget for multidisciplinary studies of
CFS, FM, and MCS together (solicitation 074&&&-9902-0005
issued 2/12/99) to better understand both their overlaps and
differences. We recommend that such three-way studies be
solicited by all federal agencies funding CFS, FM or MCS
research.
References
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Chemical Exposures and Veterans with Gulf War Illnesses.
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Signatories to the
1999 Consensus on Multiple Chemical Sensitivity
Liliane Bartha, M.D.
William Baumzweiger, M.D.
David S. Buscher, M.D.
Thomas Callender, M.D., M.P.H.
Kristina A. Dahl, M.D.
Ann Davidoff, Ph.D.
Albert Donnay, M.H.S.
Stephen B. Edelson, M.D., F.A.A.F.P., F.A.A.E.M.
Barry D. Elson, M.D.
Erica Elliott, M.D.
Donna P. Flayhan, Ph.D.
Gunnar Heuser, M.D., Ph.D., F.A.C.P.
Penelope M. Keyl, M.Sc., Ph.D.
Kaye H. Kilburn, M.D.
Pamela Gibson, Ph.D.
Leonard A. Jason, Ph.D.
Jozef Krop, M.D.
Roger D. Mazlen, M.D.
Ruth G. McGill, M.D.
James McTamney, Ph.D.
William J. Meggs, M.D., Ph.D., F.A.C.E.P.
William Morton, M.D., Dr.P.H.
Meryl Nass, M.D.
L. Christine Oliver, M.D., M.P.H., F.A.C.P.M.
Dilkhush D. Panjwani, M.D., D.P.M., F.R.C.P.C.
Lawrence A. Plumlee, M.D.
Doris Rapp, M.D., F.A.A.A., F.A.A.P., F.A.A.E.M.
Myra B. Shayevitz, M.D., F.C.C.P., F.A.C.P.
Janette Sherman, M.D.
Raymond M. Singer, Ph.D., A.B.P.N.
Anne Solomon, Ph.D., M.A.
Aristo Vodjani, Ph.D.
Joyce M. Woods, Ph.D., R.N.
Grace Ziem, M.D., Dr.P.H., M.P.H.
This article was published in the May/June 1999 issue of
Archives of Environmental Health, Vol. 54, No. 3, pp. 147–149.
Heldref Publications, Helen Dwight Reid Educational Foundation
http://www.heldref.org. The publisher grants permission for
the free reprinting and distribution of this statement.
