Toxicity of waterproofing spray is influenced by the mist particle size

In a previous study, we showed that waterproofing sprays that are toxic generate mists with smaller particles than do nontoxic products. In this study, we made 4 waterproofing sprays (A, B, C and D) with identical ingredients but with different mist particle sizes and compared the pathological changes produced in the lungs of mice. The mist particle diameters were 32.8 +/- 3.2, 62.0 +/- 3.8, 89.1 +/- 4.1 and 143.2 +/- 5.0 microns for sprays A, B, C and D, respectively. Pathological lung changes were evaluated by a 6-criteria grading system (thickening of the alveolar septum, cellular infiltrations in the alveolar septum, alteration of the bronchial mucous membrane, hyperemia of the alveolar wall, transudative hemorrhage, and alveolar collapse). Sprays A and B caused significantly greater scores as compared to the control group for all the criteria except mucosal changes, whereas the changes from sprays C and D were slight and the differences in scores were not significant. These results suggest that toxicity of waterproofing spray is influenced by the mist particle size generated and may help manufacture safer waterproofing spray products.