Chemical sensitivities and the Gulf War: Department of Veterans Affairs Research Center in basic and clinical science studies of environmental hazards

Chemical sensitivity: pathophysiology or pathopsychology?

BACKGROUND

Escalating numbers of people throughout the world are presenting to primary care physicians, allergists, and immunologists with myriad clinical symptoms after low-level exposure to assorted everyday chemicals such as smoke, perfumes, air fresheners, paints, glues, and other products. This clinical state is referred to by various diagnostic labels, including multiple chemical sensitivity disorder, environmental intolerance, chemical sensitivity (CS), and sensitivity-related illness, and has been the subject of much controversy within the health care community.

OBJECTIVE

The goal of this study was to provide a brief overview of the etiology, pathogenesis, clinical presentation, and management of CS. An evaluation of the medical community's response to this emerging diagnosis was also explored.

METHODS

This review was prepared by assessing available medical and scientific literature from MEDLINE, as well as by reviewing numerous books, toxicology journals, conference proceedings, government publications, and environmental health periodicals. A primary observation, however, is that there is limited scientific literature available on the issue of CS. The format of a traditional integrated review was chosen because such reviews play a pivotal role in scientific research and professional practice in medical issues with limited primary study and uncharted clinical territory.

RESULTS

The sensitization state of CS seems to be initiated by a significant toxic exposure, occurring as a 1-time event, or on surpassing a threshold of toxicity after toxicant accrual from repeated lower-level exposures. Once sensitized through a toxicant-induced loss of tolerance, individuals exposed to inciting triggers such as minute amounts of diverse everyday chemicals may experience various clinical and immune sequelae, sometimes involving lymphocyte, antibody, or cytokine responses. Precautionary avoidance of inciting triggers will prevent symptoms, and desensitization immunotherapy or immune suppression may improve symptoms in some cases. Sustained resolution of the CS state occurs after successful elimination of the accrued body burden of toxicants through natural mechanisms of toxicant bioelimination and/or interventions of clinical detoxification. Despite extensive clinical evidence to support the veracity of this clinical state, many members of the medical community are reluctant to accept this condition as a pathophysiologic disorder.

CONCLUSIONS

The emerging problem of ubiquitous adverse toxicant exposures in modern society has resulted in escalating numbers of individuals developing a CS disorder. As usual in medical history, iconoclastic ideas and emerging evidence regarding novel disease mechanisms, such as the pathogenesis of CS, have been met with controversy, resistance, and sluggish knowledge translation.

A Disease Register for ME/CFS: Report of a Pilot Study

Background

The ME/CFS Disease Register is one of six subprojects within the National ME/CFS Observatory, a research programme funded by the Big Lottery Fund and sponsored by Action for ME. A pilot study in East Anglia, East Yorkshire, and London aimed to address the problem of identifying representative groups of subjects for research, in order to be able to draw conclusions applicable to the whole ME/CFS population.

While not aiming for comprehensive population coverage, this pilot register sought to recruit participants with ME/CFS in an unbiased way from a large population base. Those recruited are constituting a cohort for long-term follow-up to shed light on prognosis, and a sampling frame for other studies.

Findings

Patients with unidentified chronic fatigue were identified in GP databases using a READ-code based algorithm, and conformity to certain case definitions for ME/CFS determined. 29 practices, covering a population aged 18 to 64 of 143,153, participated.

510 patients with unexplained chronic fatigue were identified. 265 of these conformed to one or more case definitions. 216 were invited to join the register; 160 agreed. 96.9% of participants conformed to the CDC 1994 (Fukuda) definition; the Canadian definition defined more precisely a subset of these. The addition of an epidemiological case definition increased case ascertainment by approximately 4%. A small-scale study in a specialist referral service in East Anglia was also undertaken.

There was little difference in pattern of conformity to case definitions, age or sex among disease register participants compared with subjects in a parallel epidemiological study who declined to participate.

One-year follow-up of 50 subjects showed little change in pain or fatigue scores. There were some changes in conformity to case definitions.

Conclusions

Objective evaluation indicated that the aim of recruiting participants with ME/CFS to a Disease Register had been fulfilled, and confirmed the feasibility of our approach to case identification, data processing, transmission, storage, and analysis. Future developments should include expansion of the ME/CFS Register and its linkage to a tissue sample bank and post mortem tissue archive, to facilitate support for further research studies.

Sensitivity-related illness: the escalating pandemic of allergy, food intolerance and chemical sensitivity

The prevalence of allergic-related diseases, food intolerance, and chemical sensitivities in both the pediatric and adult population has increased dramatically over the last two decades, with escalating rates of associated morbidity. Conditions of acquired allergy, food intolerance and chemical hypersensitivity are frequently the direct sequelae of a toxicant induced loss of tolerance (TILT) in response to a significant initiating toxic exposure. Following the primary toxicant insult, the individuals become sensitive to low levels of diverse and unrelated triggers in their environment such as commonly encountered chemical, inhalant or food antigens. Among sensitized individuals, exposure to assorted inciting stimuli may precipitate diverse clinical and/or immune sequelae as may be evidenced by clinical symptoms as well as varied lymphocyte, antibody, or cytokine responses in some cases. Recently recognized as a mechanism of disease development, TILT and resultant sensitivity-related illness (SRI) may involve various organ systems and evoke wide-ranging physical or neuropsychological manifestations. With escalating rates of toxicant exposure and bioaccumulation in the population-at-large, an increasing proportion of contemporary illness is the direct result of TILT and ensuing SRI. Avoidance of triggers will preclude symptoms, and desensitization immunotherapy or immune suppression may ameliorate symptomatology in some cases. Resolution of SRI generally occurs on a gradual basis following the elimination of bioaccumulated toxicity and avoidance of further initiating adverse environmental exposures. As has usually been the case throughout medical history whenever new evidence regarding disease mechanisms emerges, resistance to the translation of knowledge abounds.

Chronic illness as a result of low-level exposure to synthetic pyrethroid insecticides: a review of the debate

Synthetic pyrethroid insecticides are widely used in public health and agriculture throughout the world and generally considered to be the safest class of insecticides available. In contrast to this belief stands a recent debate in Germany, around possible chronic effects of exposure to low levels of pyrethroid residues, particularly in the household. The debate is reviewed with a view to its potential implications on the use of synthetic pyrethroids on insecticide-treated nets (ITNs) for malaria control. Media coverage, rather than conclusive evidence from carefully planned scientific investigations, seems the underlying factor in the debate. However, chronic effects can presently not be excluded with certainty, as relevant toxicological data do not exist in the open scientific literature. Properly designed neuro-behavioural studies on groups with long-term exposure to low doses of synthetic pyrethroids should be conducted. This will require establishment of a working definition of "case" and "exposure". Meanwhile pyrethroids should continue to be used for public health interventions that contribute substantially to morbidity and mortality reduction, such as ITNs for malaria control.

Multiple chemical sensitivity and idiopathic environmental intolerance (part two)

Multiple chemical sensitivity/idiopathic environmental intolerance (MCS/IEI) is a commonly used diagnostic term for a group of symptoms without apparent organic basis. The symptoms are characteristic of dysfunction in multiple organ systems. They wax and wane fluctuate according to exposure to low levels of chemical agents in the patient's environment, and sometimes begin after a distinct environmental change or injury such an industrial accident or chemical introduced after remodeling. Although traditional medical organizations have not agreed on a definition for this syndrome, it is being increasingly recognized and makes up an increasing percentage of the caseload at occupational/environmental medical clinics.Part two of this review article discusses diagnosis, clinical examination, long-term follow up of MCS/IEI, and the role of physicians, research on odor and treatment, diseases with similar symptoms, and further research regarding MCS/IEI patients.

JP-8 jet fuel-induced DNA damage in H4IIE rat hepatoma cells

We investigated the genotoxicity of middle distillate jet fuel, Jet Propulsion 8 (JP-8), on H4IIE rat hepatoma cells in vitro. DNA damage was evaluated using the comet (single cell gel electrophoresis) assay. Cells were exposed for 4h to JP-8 (solubilized in ethanol (EtOH) at 0.1% (v/v)) to concentrations ranging from 1 to 20microg/ml. Exposure to JP-8 resulted in an overall increase in mean comet tail moments ranging from 0.74+/-0.065 (0.1% EtOH control) to 3.13+/-0.018,4.36+/-0.32,5.40+/-0.29,7.70+/-0.52 and 11.23+/-0.77 for JP-8 concentrations 3, 5, 10, 15 and 20microg/ml, respectively. Addition of DNA repair inhibitors hydroxyurea (HU) and cytosine arabinoside (Ara-C) to cell culture with JP-8 resulted in accumulation of DNA damage strand breaks and increase in comet tail length. Inclusion of 4mM HU and 40microM Ara-C with 3, 5, 10 and 20microg/ml JP-8 concentrations resulted in increased mean tail moments to 5.94+/-0.43,10.12+/-0.72,17.03+/-0.96,and29.25+/-1.55. JP-8, in the concentrations used in this study, did not result in cytotoxicity or significant apoptosis, as measured using the terminal deoxynucleotidyl transferase (TDT)-mediated dUTP-X nick end labeling (TUNEL) assay. These results demonstrate that relevant exposures to JP-8 result in DNA damage to H4IIE cells, and suggest that DNA repair is involved in mitigating these effects.

Serum neopterin and somatization in women with chemical intolerance, depressives, and normals

The symptom of intolerance to low levels of environmental chemicals (CI, chemical intolerance) is a feature of several controversial polysymptomatic conditions that overlap symptomatically with depression and somatization, i.e., chronic fatigue syndrome, fibromyalgia, multiple chemical sensitivity, and Persian Gulf syndrome. These syndromes can involve many somatic symptoms consistent with possible inflammation. Immunological or neurogenic triggering might account for such inflammation. Serum neopterin, which has an inverse relationship with l-tryptophan availability, may offer a marker of inflammation and macrophage/monocyte activation. This study compared middle-aged women with CI (who had high levels of affective distress; n = 14), depressives without CI (n = 10), and normals (n = 11). Groups did not differ in 4 p.m. resting levels of serum neopterin. However, the CI alone had strong positive correlations between neopterin and all of the scales measuring somatization. These preliminary findings suggest the need for additional research on biological correlates of 'unexplained' multiple somatic symptoms in subtypes of apparent somatizing disorders.

Are we on the threshold of a new theory of disease? Toxicant-induced loss of tolerance and its relationship to addiction and abdiction

'Toxicant-induced loss of tolerance' (or TILT) describes a two-step disease process in which (1) certain chemical exposures, e.g., indoor air contaminants, chemical spills, or pesticide applications, cause certain susceptible persons to lose their prior natural tolerance for common chemicals, foods, and drugs (initiation); (2) subsequently, previously tolerated exposures trigger symptoms. Responses may manifest as addictive or abdictive (avoidant) behaviors. In some affected individuals, overlapping responses to common chemical, food, and drug exposures, as well as habituation to recurrent exposures, may hide (mask) responses to particular triggers. Accumulating evidence suggests that this disease process might underlie a broad array of medical illnesses including chronic fatigue, fibromyalgia, migraine headaches, depression, asthma, the unexplained illnesses of Gulf War veterans, multiple chemical sensitivity, and attention deficit disorder.

Patterns of waking EEG spectral power in chemically intolerant individuals during repeated chemical exposures

Previous studies indicate that low level chemical intolerance (CI) is a symptom of several different controversial conditions with neuropsychiatric features, e.g., chronic fatigue syndrome, fibromyalgia, multiple chemical sensitivity, and "Persian Gulf Syndrome". Prior studies suggest that limbic and/or mesolimbic sensitization may contribute to development of CI. The purpose of this report was to document the waking electroencephalographic (EEG) patterns of individuals with CI during chemical exposures presented over repeated sessions. Three groups of adult subjects who were recruited from the community participated in the study: self-reported CI who had made associated lifestyle changes due to their intolerance (CI/ LSC), self-reported CI who had not made such changes (CI), and normal controls without self-reported CI. Subjects underwent two sessions involving one-minute EEG recordings during exposures to low level chemical odors (a probe for limbic activation). The CI, but not the CI/ LSC, subjects had increased absolute delta power after the chemical exposures during the second, but not the first, session. The findings support the neural sensitization hypothesis for intolerance to low levels of environmental chemicals in vulnerable individuals. As in human studies of stimulant drug sensitization, those with the strongest past history with sensitizing agents may not show-term sensitization to low level exposures in the laboratory.

Does examination of urinary sediment identify individuals with Gulf War syndrome? A pilot study

BACKGROUND

Many veterans who were involved in the Persian Gulf theater of operations have had a variety of unexplained physical complaints, collectively called the Gulf War syndrome or similar names. There has been much debate on the issue and numerous publications, both in the medical and the lay press. A method for examining urinary sediment that was developed in an effort to identify nonculturable bacteria has been used in Gulf War veterans and was the basis for intensive antimicrobial therapy in many of them.

METHODS

We evaluated eight Gulf War veterans with complaints compatible with Gulf War syndrome. Subjects were from various parts of the United States. A detailed history and physical examination were performed. Urine was obtained before and after prostatic massage (men) or before and after pelvic examinations (women) and was tested by a previously described microscopic method as well as by culture and conventional Gram stain. Age- and sex-matched healthy control subjects were tested similarly and concurrently.

RESULTS

Two female Gulf War veterans had findings of Candida albicans and Klebsiella pneumoniae by conventional culture. The same organism types were seen both by the special method and by conventional Gram stain. All other subjects and controls were completely indistinguishable.

CONCLUSION

Examining the urinary sediment by this elaborate method does not differentiate persons with Gulf War syndrome from normal, healthy control subjects who were never in the Persian Gulf area.