A Report on Multiple Chemical Sensitivity (MCS)

The Interagency Workgroup on
Multiple Chemical Sensitivity

August 24, 1998

Predecisional Draft


MCS as a Public Health Priority

Table of Contents

IX. Findings and Recommendations


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.

Summary Findings

  • 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.

Top of Page.

MCS as a Public Health Priority

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 published findings.
  • 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 and validation.
  • 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.

Top of Page.

Return to Table of Contents

Return to Committee Reports Page