IX. Findings and
The public's concern about chemical exposures has
historical origins. Many substances that brought great benefits were later found to have
long-term risks. Substances such as lead and asbestos were widely used, and their hazards
were only slowly identified. The first recognition of concerns usually occurred in highly
exposed populations—frequently in occupational settings—among those with readily definable clinical illnesses. For
example, the carcinogenic properties of benzene were first identified by the
disproportionate occurrence of acute leukemia among persons in certain occupations.
Populations with particular susceptibilities, especially children, have also served to
alert public health officials to the dangers of certain chemical exposures. The hazards
associated with exposure to leaded paint were first dramatized by clear signs of poisoning
in young children who had high levels of exposure because they had eaten paint chips. Now,
after decades of use and widespread environmental contamination, the effects of low doses
of lead on children are widely recognized. The health of the public as a whole depends on
the vigilant monitoring of such emerging diseases and disabilities, regardless of the
extent to which medical science is able to explain their origin.
It is appropriate for public health leadership to work to mitigate illness in persons
with disorders that are not yet fully explainable. In so doing, it must be recognized that
chemical agents found to be noxious by a significant portion of the population may, and
often do, present public health hazards that lead to health concerns such as MCS.
Because of the concern for the health and well-being of persons with symptoms of MCS
and because MCS presents challenging policy issues, several Federal agencies formed a
workgroup in 1995 to review the key scientific literature pertinent to MCS, consider the
recommendations from various expert panels on MCS, review past federal actions, and
develop technical and policy recommendations.
It is currently unknown whether MCS is a distinct disease entity and what role, if any,
the biochemical mechanisms of specific chemicals have in the onset of this condition. The
workgroup finds that MCS is currently a symptom-based diagnosis without supportive
laboratory tests or agreed-upon clinical manifestations. This dependence on symptom-based
diagnosis has resulted in the absence of a uniformly agreed-upon case definition. The
workgroup could locate no previously published reports of definite end-organ damage
attributable to MCS. However, scientific knowledge changes over time as additional
findings are reported; it is therefore important not to lose sight of lessons from the
past in which suspected health effects of environmental exposures were verified at a later
date through scientific research. A summary of specific findings follows.
- No single accepted case definition of MCS has been established; proposed definitions all
differ in key criteria, and some definitions suggest a broad spectrum of possible
symptoms. The validated epidemiologic data required to clarify the natural history,
etiology, and diagnosis of MCS are not available.
- Several limitations are found in the design of many published MCS studies. Outcome
measures in some studies may be influenced by bias in subject selection, lack of
investigator blinding during patient assessment, and inconsistent quality assurance of
laboratory determinations. Certain outcome measures (e.g., functional imaging techniques)
are investigative research tools and need validation by additional studies.
- The workgroup finds that there are few data on the prevalence of MCS. Only three studies
have reported the prevalence of self-reported physician-diagnosed MCS. The prevalence of
self-reported physician-diagnosed MCS ranges from published values of 0.2 percent in
college students to 4.0 percent in elderly persons and an unpublished value of 6 percent
among randomly selected California residents.
- The amount of ongoing MCS-specific research conducted or otherwise supported by the
Federal Government is confined to a limited effort by the National Institutes of Health,
National Institute of Environmental Health Sciences (NIEHS). Other than the workgroup on
MCS, there appears to be no other Federal Government group convened expressly to examine
MCS as a medical entity of relevance to occupational and environmental health. Although
there is ancillary research at NIEHS, the Department of Veterans Affairs (DVA), and the
U.S. Environmental Protection Agency (EPA) concerning the potential relevance of advancing
the scientific database on MCS, no federal effort formulates and oversees a collaborative
MCS research plan.
- The major recommendations from several expert workshops held since 1990 are still
appropriate. These recommendations, if addressed, should advance the public health
response to the public's concerns about MCS.
- Information on the fiscal cost of MCS to society is scarce. The fiscal outlay required
for or involved in medical diagnosis and treatment of MCS needs additional study.
- Only limited efforts are being made within federal health and environmental agencies to
communicate to healthcare providers what is known and not known about MCS; these efforts
are primarily being made by the Agency for Toxic Substances and Disease Registry (ATSDR).
This lack of education for healthcare providers is accompanied by increasing public
concern about MCS.
- Numerous therapies aimed at treating MCS have been identified in the literature;
however, no widely accepted protocols are proven to be effective in addressing MCS
symptomatology. Therapeutic interventions that claim to effectively address or minimize
these impacts need objective study and validation.
- While study and validation of therapeutic interventions continue, the goal of patient
care should be to promote health without causing harm.
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MCS as a Public Health
The workgroup was aware of the many demands placed on
Federal agencies to protect the environment and the public's health. The pressure of
constrained budgets and tight personnel ceilings makes it essential that agencies
carefully weigh and prioritize research and protective actions directed toward an imposing
list of environmental problems.
The workgroup feels compelled, therefore, to comment on MCS in the context of its
priority as a national environmental health problem. Three primary circumstances usually
characterize an environmental health issue as being of high priority. First, compelling
findings from epidemiologic investigations or surveillance systems can portend
consequential health problems in human populations. An example is the identification of
the nature and extent of lead toxicity in young children through careful epidemiologic
investigations. Second, a priority environmental health problem can be identified through
clinical reports verified by the medical community. For example, clinical reports of
pesticide poisonings helped shape the understanding that contact with certain pesticides
can place pesticide applicators at risk. Third, compelling findings from basic biomedical
research may identify mechanisms of action that can translate into human health
implications. An example is the basic research on the effects of endocrine disruptors and
the implications for human reproductive and developmental health. The workgroup commends
these criteria for use in developing a strategic plan for MCS.
The workgroup concludes that the subject of MCS is unlikely to receive extensive
research support as a single entity. Personnel and budgetary resources are constrained,
and Federal agencies are attempting concurrently to evaluate a variety of syndromes that
can have disabling symptoms but lack objective clinical or laboratory evidence of disease.
Examples include CFS, fibromyalgia, and Persian Gulf War-related illnesses, and diseases
diagnosed as chronic subclinical infections.
The workgroup identified the need for an overall strategic plan for these syndromes,
including MCS, because of scientific uncertainties and unclear public health relevance
that attend each syndrome. The strategic plan should articulate the goals and objectives
of the research effort, offer guidance on the priorities and sequence for studies, present
the critical elements of study design, and reflect on appropriate resource levels. Those
involved in the strategic planning process for research should have a broad range of
knowledge and experience and represent a variety of scientific disciplines. Public input
should be a vital component of this process.
The workgroup determined that the strategic plan should consider the following
recommendations with regard to MCS research:
Research Recommendations for Consideration
- Comprehensive biomedical and clinical research is necessary for a consensus case
definition of MCS that can be used in epidemiologic studies and clinical evaluations. This
research needs to include the study of individual MCS patients under controlled
conditions. The workgroup encourages a directed effort in this area, recognizing that this
issue is a matter of policy as well as an issue of research.
- Data on the prevalence of MCS and disability related to MCS remain a key requisite for a
more informed prioritization of MCS-directed resources. The workgroup emphasizes the need
for data from representative populations selected by valid epidemiologic methods.
- Data on the role of psychosocial factors in MCS need to be gathered. The tools used to
obtain this information should be standardized and validated through the use of reference
populations, including those with well-established illnesses (e.g., allergies, asthma,
porphyria, and pesticide-related illnesses) known or reported to be associated with
susceptibility to chemical exposures. Carefully designed studies should be planned to
evaluate both the primary and secondary psychological factors in MCS.
- A targeted effort in basic research is needed to explore pathophysiologic mechanisms
that might be associated with MCS. The development and refinement of animal models that
could help identify biomarkers of susceptibility in humans is particularly important.
- MCS-related research on biomarkers should be directed as quickly as possible toward
validation studies in humans. The populations chosen for such studies should have defined
health endpoints, including MCS and other conditions (e.g., asthma and autoimmune
disorders) in which chemical exposures are suspected contributors.
- Well-coordinated, multicenter studies are encouraged to detect or exclude the subtle
effects that may be associated with low exposures and idiosyncratic reactions. Blinded
assessment, testable hypotheses, and objective outcome measures are essential to control
for experimenter bias. Federal support for MCS-related clinical research will require
stringent quality assurance of all tests under study and ongoing review of results by an
independent board, such as those established for therapeutic trials.
- Until a consensus case definition is developed, the case definition of MCS used in
research studies should be fully operational that is, it must be described in
sufficient detail to be reproducible by other investigators seeking to conform or extend
- Consideration should be given to conducting a project that collects data on MCS-relevant
health costs from sources such as states' workers compensation databases, private
insurance records, and federal and state health-care programs.
- A process of obtaining direct public input on the research and policy agenda for MCS and
enabling public participation in MCS decision making should be established. The workgroup
supports the framework for stakeholder involvement developed by the
Presidential/Congressional Commission on Risk Assessment and Risk Management (1997). The
framework encourages appropriate and feasible stakeholder involvement during all stages of
the risk management process. The framework would equally apply to stakeholder involvement
in MCS decision making.
- Because there are no widely accepted protocols that have proven to be effective in
treating MCS, the therapeutic interventions claimed to be effective need objective study
- A cross-agency evaluation of federal granting mechanisms should be conducted to ensure
that research review systems are appropriate to support basic and applied research on MCS.
Policy Recommendations for Consideration
The scientific literature is currently inadequate to enable
determination of the associations between human exposure(s) to chemicals in the
environment and the development or exacerbation of MCS. Targeted research would reduce
this uncertainty. Increased scientific knowledge about MCS and the role of environmental
chemicals will inevitably be put into the context of benefits and risk.
Virtually all chemicals in use convey both benefits and risks. Every technology, no
matter how beneficial, can exert a negative impact on some sector(s) of society. Many
chemicals have well-established toxicologic and allergenic properties; undoubtedly, others
will be found to have adverse effects in the future. Public health leaders and other risk
managers have an obligation to ensure that the benefits of technologies justify the risks.
The public health vision is health for the entire population. The reality of
public health will always involve balancing maximum benefit and minimum harm to the
public's health and well-being. Risk managers faced with decisions regarding MCS are
offered the following policy recommendations by the workgroup:
- Because of the public health issues and challenges presented by MCS, it is recommended
that phased efforts be initiated to conduct the targeted research described in the
previous section. A phased approach would make the greatest use of available resources,
and at the same time, answer key questions such as prevalence and basic mechanisms of
action that would guide follow-up research.
- There is a need to better inform the healthcare community about MCS. Health agencies
should consider a focused, limited effort in clinician education and awareness.
- Persons should not be offered ineffective, costly, or potentially dangerous treatments.
Appropriate care for well-characterized medical and psychological illnesses should not be
withheld or delayed. The ramifications of recommending functional changes in workplace or
home settings should be considered carefully. Persons identified as having MCS also need
education about what is known and not known about MCS.
- There is need for a continuing effort in interagency coordination, whether through the
workgroup or a successor group.
- An overall strategic plan for MCS and related syndromes is needed. The strategic plan
should articulate the research effort and offer guidance on communication and education of
health care providers and persons experiencing symptoms of MCS.
- The Environmental Health Policy Committee of the Department of Health and Human Services
appears to be an appropriate body for overseeing the development of an improved science
database on MCS and attendant public health responses.
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