The committee examined several cross-sectional morbidity studies of hazardous-waste sites, in which significant differences in symptoms were found between an exposed and a control population. None of these studies found differences in reproductive outcome or cancer mortality, but several documented significant self-reported symptoms including headache, irritability, and fatigue. These reports contain considerable discussion of how differences in symptom perception and recall can be avoided, but neither factor can be avoided altogether. The authors of these reports drew somewhat different conclusions from these studies, based on the degree to which they believed recall bias accounted for differences in reported symptoms. Recall bias is difficult to rule out if a community is episodically exposed to a noxious agent with a powerful odor or in other incidents of acute exposure.

Although it might be concluded that recall bias explains the symptom differences in all of the studies of self-reported symptoms, it is plausible that the symptoms complained of are more sensitive indicators of significant exposure than are more severe outcomes. The fact that disparate populations in different countries experience similar symptoms indicates that a common set of exposures may be involved. Our belief that a constellation of symptoms may be associated with airborne exposures to emissions from hazardous-waste sites relies on a number of recent studies on the sick building syndrome and other studies of neurologic symptoms in solvent-exposed workers, which have found similar effects in exposed persons in different countries. The syndrome has been firmly established for several reasons. First, a remarkable concordance has been found in the kinds of complaints made by workers in different locations and in different countries: Headaches, fatigue, inability to concentrate, and mild inflammation of the eyes and pharynx were the most common complaints. 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 “ humidifier fever” infection.

The sick building syndrome contains important lessons for hazardous-waste-site epidemiology. In many cases involving hazardous-waste sites the complaints are subjective and similar to those associated with the sick building syndrome. Furthermore, many of the volatile organic compounds found in modern sealed buildings, including formaldehyde, toluene, and trichloroethylene, also are common constituents of waste dumps.

Recent controlled exposure work from Denmark noted in Chapter 4 can play an important role in clarifying the specificity of reported



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