Allergological and toxicological aspects in a multiple chemical sensitivity cohort

Background. Multiple chemical sensitivity (MCS) is a chronic condition characterized by an exaggerated response to toxicants. We ascertained the prevalence of allergy to metals and toxicological aspects in MCS patients. Methods. We conducted a retrospective review of medical records of 41 patients with MCS. We performed patch testing (n = 21) for dental series and did lymphocyte transformation test (n = 18) for metals. We measured mercury in samples of blood (n = 19), urine (n = 19), saliva (n = 20), and scalp hair (n = 17) to investigate the association between mercury levels and cases of MCS. Results. The prevalence of metal immune hypersensitivity in a subset of 26 patients was 92.3 percent. Elevations of mercury occurred in 81.2 percent (26 of 32). The mean (±SD) in blood concentrations of mercury was 7.6 ± 13.6 μg/L; mean in urine was 1.9 ± 2.5 μg/L; mean in scalp hair was 2.2 ± 2.5 μg/g; mean in saliva was 38.1 ± 52.1 μg/L. Subgroup analyses showed that elevation of mercury levels in biological matrices were associated with mercury amalgams in patients with MCS (22 patients), compared with controls (8 patients) (odds ratio 11 : 95 percent confidence interval 1.5 to 81.6; P = 0.023). Conclusions. Our data show an increased prevalence of metal allergy and elevation of mercury levels in bioindicators among patients with MCS.

A Note on Age-Related Biomarkers

Forty-eight randomly selected age-related human biological functions were analyzed in order to establish whether or not their (linear) regressions were modified by age-related standard errors. Possible reasons for this are advanced. Statistically significant multiple regressions were obtained in 25%, and 21% of the functions yielded statistically significant changes in the correlations between data and age when partial correlation coefficients were calculated. The conclusion is that age-related data need to be subjected to the above tests in order to minimize confounding factors.

Mechanisms of multiple chemical sensitivity

Sensitivity to chemicals is a toxicological concept, contained in the dose-response relationship. Sensitivity also includes the concept of hypersensitivity, although controversy surrounds the nature of effects from very low exposures. The term multiple chemical sensitivity has been used to describe individuals with a debilitating, multi-organ sensitivity following chemical exposures. Many aspects of this condition extend the nature of sensitivity to low levels of exposure to chemicals, and is a designation with medical, immunological, neuropsychological and toxicological perspectives. The basis of MCS is still to be identified, although a large number of hypersensitivity, immunological, psychological, neurological and toxicological mechanisms have been suggested, including: allergy; autosuggestion; cacosomia; conditioned response; immunological; impairment of biochemical pathways involved in energy production; impairment of neurochemical pathways; illness belief system; limbic kindling; olfactory threshold sensitivity; panic disorder; psychosomatic condition; malingering; neurogenic inflammation; overload of biotransformation pathways (also linked with free radical production); psychological or psychiatric illness; airway reactivity; sensitisation of the neurological system; time dependent sensitisation, toxicant induced loss of tolerance. Most of these theories tend to break down into concepts involving: (1) disruption in immunological/allergy processes; (2) alteration in nervous system function; (3) changes in biochemical or biotransformation capacity; (4) changes in psychological/neurobehavioural function. Research into the possible mechanisms of MCS is far from complete. However, a number of promising avenues of investigation indicate that the possibility of alteration of the sensitivity of nervous system cells (neurogenic inflammation, limbic kindling, cacosomia, neurogenic switching) are a possible mechanism for MCS.

Epidemiology of sick building syndrome and its associated risk factors in Singapore

OBJECTIVES

To investigate the occurrence of sick building syndrome in a tropical city, and its relation to indoor air quality and other factors.

METHODS

2856 office workers in 56 randomly selected public and private sector buildings were surveyed. The study consisted of a self administered questionnaire assessing symptoms and perception of the physical and psychosocial environment, inspection of the building plans and premises, and measurement of temperature, relative humidity, respirable particles, chemicals, bioaerosols, and other variables.

RESULTS

Symptoms typical of the sick building syndrome were reported in 19.6% of the respondents. Multivariate modelling substantiated contributions associated with low thermal comfort, high work related stress, too much noise, a history of allergy or other medical conditions, poor lighting, young employees, and female sex. Measurements of indoor air quality or ventilation were not found to be reliable predictors of the symptoms.

CONCLUSION

The survey confirmed the presence of sick building syndrome and its risk factors in the tropics. A biopsychosocial approach to the problem involving symptomatic treatment, environmental control, good ergonomic design, and stress management is recommended.

Applied epidemiology and environmental health: emerging controversies

This review article assesses the state of the science in environmental epidemiology, not by summarizing current scientific findings but rather by examining conceptual controversies in the study of how environmental factors influence human health. This approach seems necessary because environmental epidemiology presently stands at a crossroads-in fact, at a number of overlapping crossroads. The field teems with epistemologic debates concerning appropriate paradigms for framing research questions, interpreting data, and applying research findings to policy. The present review focuses on emerging controversies related to three questions: What is considered "environmental"? What counts as credible research in environmental epidemiology? And what does "applied epidemiology" mean in the context of environmental health? The goal is to organize the presently fragmented critical literature on these issues and to promote productive dialogue by identifying central themes in current conceptual debates.