Abstract
Recently, health damage to children exposed to synthetic polyurethane (PU) running tracks has aroused social panic in China. Some possible toxic volatiles may be responsible for these damages. However, the exact cause remains unclear. We have detected a low concentration of sulfur dioxide (SO2; 1.80-3.30 mg/m3) on the surface of the PU running track. Surprisingly, we found that SO2 was generated from the PU running track, and even such a low concentration of SO2 could induce severe lung inflammation with hemorrhage, inflammatory cell infiltration, and inflammatory factor secretion in mice after 2-week exposure. Prolonged exposure (5 weeks) to the SO2 caused chronic pulmonary inflammation and pulmonary fibrosis in the mice. Peripheral hemogram results showed that platelet concentration increased significantly in the SO2 group compared to that in the control group, and the proportion of blood neutrophils and monocytes among total leukocytes was more imbalanced in the SO2 group (16.6%) than in the control group (8.0%). Further histopathology results of sternal marrow demonstrated that hematopoietic hyperplasia was severely suppressed with increased reticular stroma and adipocytes under SO2 exposure. These data indicate that a low concentration of SO2 generated spontaneously from PU running track outdoors as a secondary product is still harmful to health, as it impairs the respiratory system, hematopoiesis, and immunologic function. This indicates that the low-concentration SO2 could be a major cause of diseases induced by air pollution, such as chronic obstructive pulmonary disease.