Background and purpose: We assessed the signs and symptoms, pulmonary function changes and residual chemical body burden of school children in the vicinity of an accidental exposure to volatile xylene and methylene diphenyl diisocyanate (MDI).
Methods: After the exposure episode, children with significant symptoms after MDI exposure (e.g., dizziness, nausea, sore throat, and breathing difficulties) were sent to nearby emergency medical units for evaluation and admission if necessary. Clinical work-up included pulmonary function tests and measurement of residual MDI in the body by high-performance liquid chromatography analysis of urine.
Results: 203 students appeared to develop symptoms associated with contaminant exposure, and 173 affected students were sent to nearby emergency units. In the subsequent surveillance, 22 of 203 affected students (10.8%) revealed a positive history of asthma, which was strongly correlated with the incidence of dyspnea arising from the incident. For children with no previous history of asthma, 60.8% (110 of 181) complained of dyspnea during the episode, and 16.2% required inhaled bronchodilator therapy at the emergency medical units for relief of wheezing symptoms. In a simulation, we found the raw material used for tract surfacing, primarily MDI dissolved in xylene, to be present at a concentration (870 ppm w/w) more than 8000-fold the level defined as safe for a working environment.
Conclusions: We have detected a direct cause-effect relationship between the accidental spillage of MDI and the appearance of an acute asthma-like syndrome among previously unexposed school children.