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PubMedDate not supplied

Multiple chemical sensitivity as a conditional response.

Pavlovian conditioning may contribute to some cases of multiple chemical sensitivity (MCS). On the basis of the conditioning analysis, environmental stimuli (especially olfactory cues) present at the time of a toxicant overdose become associated with the toxicant and elicit aversive conditional responses. Similar associations have been reported in patients receiving chemotherapy, and the literature on such 'pretreatment nausea' in cancer patients is relevant to understanding the role of conditioning in MCS. Evaluation of the contribution of conditioning to MCS has been complicated by confounding interpretations that emphasize conditional responses with interpretations which emphasize the psychiatric status of the patient. Appreciation of the contribution of Pavlovian conditioning to MCS will lead to a better understanding of this complex disorder.

Animals↗
PubMed1994

Multiple chemical sensitivity syndrome: a clinical perspective. II. Evaluation, diagnostic testing, treatment, and social considerations.

Multiple chemical sensitivity syndrome (MCS) does not appear to fit established principles of toxicology. Social, political, and economic forces are demanding that MCS be defined medically, even though scientific studies have failed as yet to identify pathogenic mechanisms for the condition or any objective diagnostic criteria. Consequently, a working definition of MCS can only rely on a person's subjective symptoms of distress and attribution to environmental exposures rather than currently measurable objective evidence of disease. Nevertheless, patients labeled with MCS are clearly distressed and many are functionally disabled. Without reconciling the different theories of etiology of MCS discussed in Part I of this report, and recognizing that the cause of the syndrome may be multifactorial, strategies are proposed for clinical evaluation and management of patients with MCS using a biopsychosocial model of illness. The social implications of this illness are also discussed.

Health Policy↗
PubMedDate not supplied

Rhinolaryngoscopic examination of patients with the multiple chemical sensitivity syndrome.

Ten patients who met the Cullen case definition for the multiple chemical sensitivity syndrome were evaluated; a history was taken, and physical examination and fiberoptic rhinolaryngoscopy were performed. All patients had an initial chemical exposure, which was followed by multiple physical and mental complaints in response to subsequent exposure to a variety of odorous organic chemicals. Rhinitis was a prominent complaint in nine patients, but one patient denied any nasal symptoms. Rhinolaryngoscopic findings were abnormal in all patients; edema, excessive mucus, a cobblestone appearance of the posterior pharynx and base of the tongue, and mucosal injection were observed frequently. A particularly striking finding was focal areas of blanched mucosa that surrounded a prominent vessel. These results suggest that nasal pathology may be a prominent feature of this disorder.

Adult↗
PubMed2006

Chemosensory function and psychological profile in patients with multiple chemical sensitivity: comparison with odor-sensitive and asymptomatic controls.

OBJECTIVE: We addressed the question if patients with multiple chemical sensitivity (MCS) differ from participants with self-reported odor sensitivity without MCS and asymptomatic controls in terms of chemosensory, cognitive, and clinical psychological endpoints. METHODS: In a clinical study 23 MCS patients, 21 participants with self-reported odor sensitivity, and 23 controls were investigated using electrophysiological and psychophysical olfactometric tests [chemosensory-event-related potentials (CSERP), olfactory thresholds, odor identification, trigeminal sensitivity]. The participants filled in a mood list, a list of complaints (BL), a Symptom Check List, a State-Trait Anxiety Inventory (STAI), and an MCS questionnaire. RESULTS: The olfactometric investigations revealed no significant differences between the groups. The MCS group reached significantly higher scores on negative mood states following odorant exposure, on health complaints, global indices, and the somatization subscale of the Symptom Check List, trait and state anxiety and symptoms, and triggering matters of the MCS questionnaire. CONCLUSIONS: Our findings reveal that neither olfactory functions, nor chemosensory or cognitive olfactory information processing are impaired in MCS patients. They rather support findings of altered psychological profile and moderate psychopathology.

Adult↗
PubMed1994

Multiple chemical sensitivity syndrome: a clinical perspective. I. Case definition, theories of pathogenesis, and research needs.

Multiple chemical sensitivity syndrome (MCS) does not appear to fit established principles of toxicology. Yet social, political, and economic forces are demanding that MCS be defined medically, even though to date scientific studies have not identified pathogenic mechanisms for the condition or any objective diagnostic criteria. Consequently, a working definition of MCS can rely only on an individual's subjective symptoms of distress and attribution to environmental exposures rather than currently measurable objective evidence of disease. Nevertheless, patients labeled with MCS are clearly distressed and many are functionally disabled. In this review, four theories of causation are explored: (1) MCS is a purely biologic/physical or psychophysiologic reaction to low-level chemical exposures. (2) MCS symptoms may be elicited by low-level environmental chemical exposures, but the sensitivity is initiated by psychologic stress. (3) MCS is a misdiagnosis and chemical exposure is not the cause. The symptoms may be due to misdiagnosed physical or psychologic illness. (4) MCS is an illness belief system manifest by culturally shaped illness behavior. Areas for further research regarding the etiologies of MCS are suggested. Recognizing that the cause of the syndrome may be multifactorial, strategies are proposed for clinical evaluation and management in Part II of this manuscript using a biopsychosocial model of illness.

Humans↗
PubMed1997

Panic response to sodium lactate infusion in patients with multiple chemical sensitivity syndrome.

BACKGROUND: Many patients who are first seen with what has been called multiple chemical sensitivity syndrome (MCS) experience symptoms suggestive of panic disorder including chest tightness, shortness of breath, palpitations, paresthesias, light-headedness, and mental confusion. Although such patients are often convinced that these symptoms reflect toxic effects of environmental "chemicals," direct evidence of this is lacking. To the contrary, a previous study has shown that some of these individuals exhibit hyperventilation responses on exposure to non-noxious stimuli, and it has been suggested that the resulting hypocarbia accounts for their symptoms. We postulated that some patients with self-identified MCS had an underlying condition similar to panic disorder and would therefore demonstrate similar responses to provocative challenges, such as sodium lactate infusion. METHODS: Patients referred to an allergy and clinical immunology service for evaluation of "chemical sensitivity" were investigated to rule out underlying medical conditions, including asthma, as a cause of their symptoms and were enrolled for study after giving informed consent. After a standardized psychiatric assessment was performed, patients underwent single-blind intravenous infusions of normal saline solution (placebo) and sodium lactate (which reproduces symptoms in individuals with underlying panic disorder). All patients were referred for independent psychiatric assessment. RESULTS: The standardized psychiatric assessment identified four of five patients as meeting DSM III-R diagnostic criteria for panic disorder along with other depressive and/or anxiety-related disorders. All five patients with self-identified chemical sensitivity exhibited a positive symptomatic response to sodium lactate compared with placebo infusion. Independent psychiatric assessment confirmed the diagnosis of panic disorder on the basis of DSM III-R criteria in each of the five patients. CONCLUSION: These results suggest that MCS may have a neurobiologic basis similar, if not identical, to that of panic disorder. We speculate that treatments with demonstrated efficacy in panic disorder may also be of benefit in MCS, and conversely, treatments that reinforce anticipatory anxiety and avoidance behavior in patients with MCS may be detrimental.

Adult↗
PubMed2003

[Multiple chemical sensitivity. Is the patient suffering as a result of environmental pollutants or psychological problems?].

Multiple chemical sensitivity (MCS) poses a medical challenge. Proposed etiologies are as numerous as they are contradictory, direct and indirect costs are high, and patient suffering considerable. In the absence of objective diagnostic criteria, estimation of its prevalence is difficult. Nevertheless, establishment of the diagnosis is frequently strikingly uncritical. We support an holistic approach that gives consideration both to psychological and physical aspects, as well as taking account of the high level of comorbidity, and we warn against "over-diagnosis". Therapeutical approaches should consider carefully the risk of avoidance and social withdrawal.

Air Pollutants↗
PubMed1996

Proposed animal neurosensitization model for multiple chemical sensitivity in studies with formalin.

A potentially promising line of animal research relevant to multiple chemical sensitivity (MCS) is that of sensitization in the central nervous system (CNS), particularly limbic pathways in the brain. Sensitization is the progressive and enduring enhancement in behavioral and neurochemical responses that occurs after repeated exposure to psychostimulants or environmental stressors. Since the onset and progression of sensitization has many parallels with that of MCS, it has been proposed that MCS may be initiated through a mechanism similar to the sensitization of CNS components occurring in the rodent. To test this hypothesis, female Sprague-Dawley rats were exposed to formalin vapors (FORM, 11 ppm) or water vapor (control) 1 h/day for 7 days. The next day, a saline injection was given followed by a cocaine injection (15 mg/kg, i.p.) 24 h later, and locomotor activity was monitored. Animals pretreated with repeated FORM inhalation demonstrated a significantly enhanced locomotor response to cocaine compared to controls, an indicator that specific limbic pathways may have been sensitized. At 4 weeks of withdrawal from FORM exposure, a subset of animals remained sensitized to a cocaine challenge. No differences were found between groups after a saline injection. In a second experiment, animals were screened prior to FORM or water exposure for their response to a novel situation, a measure believed to reflect an animal's general responsiveness to stimuli. Rats were divided into high responders (HR) or low responders (LR), based on their locomotion in a novel cage. Results from three behavioral tests demonstrated that HR and LR were differentially affected by exposure to FORM. In a passive avoidance test, HR and LR appeared to be different in their distribution of responses, while HR and LR responses in the FORM group were nearly identical. On the elevated plus maze test of anxiety, HR spent more time on the open arms than LR in both treatment groups, with significant differences between HR and LR in the FORM, but not water, treated group. On a hot plate test to measure nociceptive levels, no differences occurred between HR and LR in the control group, whereas nociception of LR tended toward an increase compared to HR in the FORM-exposed group. Results from the second experiment suggest that the effects of FORM exposure may be obscured by examining behavior in a heterogeneous population (HR and LR). This approach using animal models may help define neural substrates that mediate the amplification of responses of a subpopulation of individuals to chemicals in the environment.

Animals↗
PubMed1999

Links between multiple chemical sensitivity and asthma in a rat model of cholinergic hypersensitivity: a brief review.

Individuals with multiple chemical sensitivity (MCS) also commonly report symptoms of asthma, but, as far as we have been able to determine, no one has yet suggested that an abnormal cholinergic system may provide the link between asthma and MCS. The present brief review provides evidence for such a link by summarizing recent findings in a genetic animal model of cholinergic hyperresponsiveness. The Flinders Sensitive Line (FSL) rats were developed by selective breeding for increased responses to an anticholinesterase agent similar to commonly used organophosphate pesticides. Relative to their control line, the Flinders Resistant Line (FRL) rats, the FSL rats are more sensitive to drugs that stimulate acetylcholine receptors, alcohol, diazepam, and drugs that have a selective effect on dopamine or serotonin receptors. These findings raise the possibility that the FSL rats may resemble individuals with MCS. Hyperresponsiveness of the airways is a hallmark of asthma. The procedure known as whole-body plethysmography, where breathing can be monitored in freely moving animals, was employed to study the FSL and FRL rats. The FSL rats exhibited a greater index of bronchoconstriction than the FRL rats in response to both a cholinergic agonist and an allergen challenge. Thus, the FSL rats are more sensitive both to a variety of drugs unrelated to the cholinergic system and to cholinergic- and allergen-induced bronchoconstriction. An abnormal cholinergic system may therefore contribute to both MCS and asthma.

Animals↗
PubMed2003

Breathing and heart rate during experimental solvent exposure of young adults with self-reported multiple chemical sensitivity (sMCS).

This paper deals with the assumption that young adults with self-reported multiple chemical sensitivity (sMCS) show a heightened sensitivity of autonomic functions during experimental solvent exposure. Male sMCS-subjects were selected (out of n=274) on the base of a German questionnaire on chemical and environmental sensitivity (CGES). Two independent experiments were carried out, each with 12 sMCS-subjects and 12 age-matched control-subjects. In experiment I two concentrations of the solvents ethyl benzene (10 and 98 ppm) and 2-butanone (10 and 189 ppm) were used. Experiment II investigated 2-propanol (35 and 190 ppm) and 1-octanol (0.1 and 6.4 ppm). The low concentrations correspond nearly to the olfactory thresholds while the high concentrations correspond to the German occupational threshold limit values (MAC). The exposure duration under each condition was 4h. The sequence of the four exposure conditions was random including intervals of at least 2 days without exposure. During the exposure physiological changes of breathing rate and heart rate were recorded. Two 30 min intervals with a sedentary position of the subjects at the beginning and end of exposure were chosen for analyses. Neither in experiment I nor in experiment II significant specific reactions to the type or level of the exposures were found. The autonomic functions in both experiments revealed alterations within the exposure sessions. The heart rate in experiment II and the breathing rate in both experiments decreased significantly during the analyzed 30 min intervals. Furthermore, in both experiments the heart rates decreased significantly from beginning to end of exposure. Only in experiment I the mean breathing rate of sMCS-subjects was generally higher compared to the control-subjects. Regarding the assumption of a heightened sensitivity of sMCS-subjects the two experiments yielded controversial results. Thus, the hypothesis of stronger responses of autonomic functions of sMCS-subjects provoked by various exposure scenarios remains open.

Adult↗
PubMedDate not supplied

Multiple chemical sensitivity: discriminant validity of case definitions.

In this study, the authors used the University of Toronto's Health Survey self-administered questionnaire to determine discriminant validity of multiple chemical sensitivity definitions. The authors distributed a total of 4,126 questionnaires to adults who attended general, allergy, occupational, and environmental health practices. The authors then matched responses to features selected from existing case definitions posited by Thomson et al.; the National Research Council; Cullen; Ashford and Miller; Randolph; Nethercott et al.; and the 1999 Consensus (references 4-7, 2, 9, and 10, respectively, herein). The overall response rate was 61.7%. The prevalence of reported symptoms was lowest in general practices, was intermediate in occupational health and allergy practices, and was highest in environmental health practices. Features from the definitions presented by Nethercott et al. and the 1999 Consensus (references 9 and 10, respectively, herein) correctly identified more than 80% of environmental health practice patients and more than 70% of general practice patients. Combinations of 4 symptoms (i.e., having a stronger sense of smell than others, feeling dull/groggy, feeling "spacey," and having difficulty concentrating) also discriminated successfully. In summary, features from 2 of 7 case definitions assessed by the University of Toronto Health Survey achieved good discrimination and identified patients with an increased likelihood of multiple chemical sensitivity.

Adolescent↗
PubMedDate not supplied

A nine-year follow-up of people diagnosed with multiple chemical sensitivities.

The authors assessed self-reported health status and clinical symptoms in people reporting multiple chemical sensitivities (MCS) at a 9-year follow-up interview using structured and semistructured instruments and self-report questionnaires. Of the original sample, 18 people (69%) consented to an interview. By use of the best estimate diagnostic method, 15 subjects (83%) met DSM-IV criteria for a lifetime mood disorder, 10 (56%) for a lifetime anxiety disorder, and 10 (56%) for a lifetime somatoform disorder. None of the subjects met the criteria for a substance use disorder (current or lifetime). The Illness Behavior Questionnaire and the Symptom Check-list-90-Revised results showed little change from 1988 and remained significantly different from the control group on many subscales. The authors conclude that the subjects remain strongly committed to the diagnosis of MCS, and although improved since their original interview, many remain symptomatic and continue to report ongoing lifestyle changes.

Adult↗
PubMedDate not supplied

Development of multiple chemical sensitivities in laborers after acute gasoline fume exposure in an underground tunneling operation.

In this article, investigators report on the presence and nature of chemical sensitivities and other indices of illness in a cohort of workers excavating a new subway tunnel located under a former gasoline station. The workers were exposed to gasoline fumes for up to approximately 2 mo when they inadvertently dug into soil contaminated by gasoline. The cohort was unique in several ways: (a) contact with gasoline was made by the workers at a time when no one had complained of multiple chemical sensitivities syndrome; (b) all were males of low socioeconomic status; (c) the exposure was well documented; (d) the cohort could be considered "naive" because, at the time of the study, the men were not members of support groups and were not being seen by clinical ecologists, and they were not labeled, either by self or others, as having multiple chemical sensitivities syndrome or any related diagnosis; and (e) at the time of interview, all workers we contacted appeared to be either gainfully employed or laid off temporarily and seeking gainful employment. We explored the health status of the workers at two different times: (1) soon after the tunnel was closed as a result of high, measured benzene-exposure levels and (2) 10-13 mo after the tunnel was closed. The workers were chronically overexposed to gasoline fumes, after which approximately one-fourth (26.7%) of our random sample of relatively naive, low-socioeconomic-status male laborers-although neither disabled nor generally litigious-reported the new onset of chemical hypersensitivities and other characteristics that fit conservative criteria for multiple chemical sensitivities syndrome.

Adult↗
PubMed1998

Integrated defense system overlaps as a disease model: with examples for multiple chemical sensitivity.

The central nervous, immune, and endocrine systems communicate through multiple common messengers. Over evolutionary time, what may be termed integrated defense system(s) (IDS) have developed to coordinate these communications for specific contexts; these include the stress response, acute-phase response, nonspecific immune response, immune response to antigen, kindling, tolerance, time-dependent sensitization, neurogenic switching, and traumatic dissociation (TD). These IDSs are described and their overlap is examined. Three models of disease production are generated: damage, in which IDSs function incorrectly; inadequate/inappropriate, in which IDS response is outstripped by a changing context; and evolving/learning, in which the IDS learned response to a context is deemed pathologic. Mechanisms of multiple chemical sensitivity (MCS) are developed from several IDS disease models. Model 1A is pesticide damage to the central nervous system, overlapping with body chemical burdens, TD, and chronic zinc deficiency; model 1B is benzene disruption of interleukin-1, overlapping with childhood developmental windows and hapten-antigenic spreading; and model 1C is autoimmunity to immunoglobulin-G (IgG), overlapping with spreading to other IgG-inducers, sudden spreading of inciters, and food-contaminating chemicals. Model 2A is chemical and stress overload, including comparison with the susceptibility/sensitization/triggering/spreading model; model 2B is genetic mercury allergy, overlapping with: heavy metals/zinc displacement and childhood/gestational mercury exposures; and model 3 is MCS as evolution and learning. Remarks are offered on current MCS research. Problems with clinical measurement are suggested on the basis of IDS models. Large-sample patient self-report epidemiology is described as an alternative or addition to clinical biomarker and animal testing.

Acute-Phase Reaction↗
PubMed2001

Repeated formaldehyde effects in an animal model for multiple chemical sensitivity.

Chemical intolerance is a phenomenon observed in multiple chemical sensitivity (MCS) syndrome, an ill-defined disorder in humans attributed to exposure to volatile organic compounds. Amplification of symptoms in individuals with MCS resembles the phenomenon of psychostimulant- and stress-induced sensitization in rodents. We have recently tested in rats the hypothesis that repeated chemical exposure produces sensitization of central nervous system (CNS) circuitry. A rat model of MCS in our laboratory has employed several endpoints of CNS function after repeated formaldehyde (Form) exposure (1 h/day x 5 days/week x 4 weeks). Repeated Form exposure produced behavioral sensitization to later cocaine injection, suggesting altered dopaminergic sensitivity in mesolimbic pathways. Rats given repeated Form also demonstrated increased fear conditioning to odor paired with footshock, implicating amplification of neural circuitry guiding fear responding to a conditioned odor cue. Recent studies examining the effects of repeated Form on locomotor activity during each daily exposure showed a decrease in rearing activity after 12-15 days of Form exposure compared to air-exposed controls. EEG recordings taken 1 week after withdrawal from daily Form revealed altered sleep architecture. Some of the differences in sleep disappeared after subsequent brief (15 min) challenge with Form the next day. Overall, the findings indicate that repeated low-level chemical exposure produces behavioral changes that may be akin to those observed in individuals with MCS, such as greater sensitivity to chemicals manifest as increased anxiety upon chemical exposure and altered sleep and/or fatigue. Study of the underlying CNS changes will provide a basis for mechanistically based animal models for MCS.

Animals↗
PubMed2006

Multiple chemical sensitivities: A systematic review of provocation studies.

A systematic review of provocation studies of persons reporting multiple chemical sensitivities (MCS) was conducted from databases searched from inception to May 2006. Thirty-seven studies were identified, testing 784 persons reporting MCS, 547 control subjects, and 180 individuals of whom a subset were chemically sensitive. Blinding was inadequate in most studies. In 21 studies odors of chemicals were probably apparent; 19 of these reported positive responses to provocations among chemically sensitive individuals, and 1 study demonstrated that negative expectations were significantly associated with increased symptom reporting after provocations. Seven studies used chemicals at or below odor thresholds, and 6 failed to show consistent responses among sensitive individuals after active provocation. Six studies used forced-choice discrimination and demonstrated that chemically sensitive individuals were not better at detecting odor thresholds than nonsensitive participants. Three studies tested individuals by using nose clips/face masks and confirmed response, possibly mediated through eye exposure. Three studies used olfactory masking agents to conceal stimuli, and none of these found associations between provocations and response. We conclude that persons with MCS do react to chemical challenges; however, these responses occur when they can discern differences between active and sham substances, suggesting that the mechanism of action is not specific to the chemical itself and might be related to expectations and prior beliefs.

Databases as Topic↗
PubMed2004

Prevalence of multiple chemical sensitivities: a population-based study in the southeastern United States.

We examined the prevalence of multiple chemical sensitivities (MCS), a hypersensitivity to common chemical substances. We used a randomly selected sample of 1582 respondents from the Atlanta, Ga, standard metropolitan statistical area. We found that 12.6% of our sample reported the hypersensitivity and that, while the hypersensitivity is more common in women, it is experienced by both men and women of a variety of ages and educational levels. Our prevalence for MCS is similar to that (15.9%) found by the California Department of Health Services in California and suggests that the national prevalence may be similar.

Adolescent↗