Applying Urinary Biomarkers of 11-dehydrothromboxane B2 and 8-isoprostane to Understand the Health Effects of PM2.5 and Ozone Exposure

Background: Using urine has many advantages over using other biological specimens for biomonitoring of exposure and health effects. Urinary 8-isoprostane can reflect lipid oxidation damage and 11-dehydrothromboxane B2 (11dhTxB2) can reflect platelet activation. Urinary 11dhTxB2 and urinary 8-isoprostane have rarely been applied to studies of air pollution exposure and its health effects. Lipid oxidation and platelet activation are the potential pathophysiological mechanisms by which air pollution exposure causes various respiratory and cardiovascular diseases. This study applies the two urinary biomarkers to assess the health effect of short term PM2.5 and ozone exposure.

Method: 89 healthy individuals (age>18years old) were recruited and divided into 2 groups. During the study, air purifiers were manipulated differently based on the group. Each participant's pollutant exposure was calculated using time-activity data and the concentration of pollutants. The urine samples were collected before and after each manipulation of air purifiers. The concentration of two urinary biomarkers were analyzed by HPLC coupled with mass spectrometers and normalized by urine specific gravity. The data of both biomarkers, exposures, and other information of the participants were analyzed using the R statistical software.

Results: 12-hour, 24-hour and 2-week ozone (O3) exposure showed significant correlations with the level of urinary 8-isoprostane. One IQR (5.69µg/m3) increase of 12-h ozone exposure was associated with an increase in 8-isoprostane level by 28.48% ( 95% Cl: 18.79%, 38.32%, p-value <0.01). One IQR (6.98 µg/m3) incremental change of 24-h O3 exposure was associated with a 27.54% ( 95% Cl: 15.66%, 39.62%, p-value <0.05) increase in 8-isoprostane level. One IQR (4.47 µg/m3) incremental change of 2-week ozone exposure was associated with a 55.28% ( 95% Cl: 38.95%,72.16%, p-value <0.05 ) increase in urinary concentration of 8-isoprostane. One IQR (4.47 µg/m3) incremental change of 2-week ozone exposure was associated with an increase in 11dhTxB2 level by 22.33% ( 95% Cl: 13.64%,31.18%, p-value <0.01 ). PM2.5 exposure showed no significant correlation with either biomarker.

Conclusion: Short-term ozone exposure was associated with lipid peroxidation and platelet thromboxane generation, reflected by increased concentrations of urinary 8-isoprostane and 11dhTxB2 associated with increasing exposure.