tions and in different countries: Headaches, fatigue, inability to concentrate, and mild inflammation of the eyes and pharynx were the most common complaints (Mendell and Smith, 1990). The complaints were generally more common in air-conditioned buildings, and they could not be attributed to fungi (such as Aspergillus) known to be responsible for the infection “humidifier fever.” Work from Denmark (Molhave, 1985; Kjaergaard et al., 1989) has not only identified a group of volatile organic compounds most commonly present when complaints are recorded, but has shown that controlled exposures to these compounds (and not to others) elicit the same symptoms in groups of subjects who might or might not have reported adverse symptoms previously. The recent controlled-exposure study of n-decane (common in building materials) from the Aarhus group (Kjaergaard et al., 1989) provides an excellent example of how subjective symptoms, such as eye irritation, can be objectively studied. Effects on humans were demonstrated at 1/500th of the exposure level that produced effects on rats. In the study, 63 healthy subjects randomly selected from the regular Danish population were exposed to n-decane in concentrations of 10, 35, or 100 microliters/liter in a controlled double-blind study. Subjects were exposed for 6 hours per exposure day for a total of 4 exposure days. Dose-dependent changes in irritation of mucous membranes (measured by decreased tear film stability and an increase in conjunctival polymorphs), as well as subjective observations of increased sensation of odor intensity and perception of reduced air quality, were documented.

Diary data also can be used to compare complaints of symptoms that arise from working in new office buildings (Mendell and Smith, 1990). Reports of similar symptoms (fatigue, headache, and inability to concentrate) by populations in North American and European cities lends credibility to the phenomenon being reported.

Although the unravelling of the genesis of this syndrome is not yet complete, it contains important lessons for studies of hazardous-waste-site epidemiology. In many cases involving hazardous-waste sites, the complaints are subjective and similar to those of the sick building syndrome. In addition, objective markers of exposure have not been identified. Furthermore, many of the volatile compounds found in sealed modern buildings, including formaldehyde, toluene, and trichlorethylene, also are common constituents of waste dumps.

It has recently been suggested that exposure to low levels of formaldehyde is followed by changes in cells that indicate that the immune system has been affected (Thrasher et al., 1987). Although the precise significance of such changes is unclear, the possibility must

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