METHODOLOGICAL ISSUES IN HUMAN EXPOSURE STUDIES OF LOW-LEVEL SOLVENT MIXTURES

Assessment of sensory irritant and neurobehavioural effects of exposure to complex solvent mixtures poses a variety of methodological challenges, particularly at the low levels typically found in new buildings. Healthy young adult males were exposed to a 25mg/m3 mixture of 22 volatile organic compounds (VOCs) representative of the highest concentration found in new homes. This concentration is equivalent to about 7ppm toluene. This mixture produced no consistent effects on performance of an extensive neurobehavioural battery, but did elicit classical "sick building syndrome" (SBS) symptoms of eye and throat irritation, headache and fatigue. Failure to find functional deficits could be due to several factors: (1) The neurobehavioural tests may not have been sensitive (or difficult) enough to detect effects; (2) healthy young adult males are probably the least likely subset of the general population to show performance decrements. Further study is needed to determine which subsets are most vulnerable to low-level solvent exposure; (3) finally, low-level VOC mixtures may not be neurotoxic. Other physiological endpoints (e.g. inflammatory response and pulmonary function), need to be explored.