A Report on Multiple Chemical Sensitivity (MCS)

The Interagency Workgroup on
Multiple Chemical Sensitivity

August 24, 1998

Predecisional Draft

Table of Contents


The workgroup reviewed the scientific literature pertinent to multiple chemical sensitivity (MCS), considered recommendations from various expert panels on MCS, reviewed past and current federal actions, and developed technical and policy recommendations. The workgroup considers policy makers and researchers at agencies concerned with MCS issues to be the primary audience for this report.

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 signs of clinical manifestation. The workgroup knows of no reports in the literature 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.

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MCS ranges from published values of 0.2 percent in college students to 4.0 percent in elderly persons and an unpublished value of 6 percent among randomly selected California residents.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 health-care 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 health-care 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.

The workgroup concluded that the subject of MCS is unlikely to receive extensive research support as a single entity. Existing personnel and budgetary resources are constrained, and Federal agencies are attempting concurrently to evaluate a variety of syndromes that present with disabling symptoms but lack objective clinical or laboratory evidence of disease. Examples include chronic fatigue syndrome, fibromyalgia, 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. Persons involved in the strategic planning of 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.

In the context of an overall research strategy, a number of research areas pertinent to MCS were discussed by the workgroup. These areas are found in Section IX and are suggested for consideration for their relevance as part of any MCS strategic plan.

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 healthcare 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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