Differential oxidative stress response in young children and the elderly following exposure to PM2.5

Objectives  The mechanism of the adverse health effects of ambient particulate matter on humans has not been well-investigated despite many epidemiologic association studies. Measurement of personal exposure to particulate pollutants and relevant biological effect markers are necessary in order to investigate the mechanism of adverse health effects, particularly in fragile populations considered to be more susceptible to the effects of pollutants. Methods  We measured personal exposure to PM_2.5 and examined oxidative stress using urinary malondialdehyde three times in 51 preschoolers and 38 elderly subjects. A linear mixed-effects model was used to estimate PM_2.5 effects on urinary MDA levels. Results  Average personal exposure of the children and elderly to PM_2.5 was 80.5 ± 29.9 and 20.7 ± 12.7 μg/m³, respectively. Mean urinary MDA level in the children and the elderly was 3.6 ± 1.9 and 4.0 ± 1.6 μmol/g creatinine. For elderly subjects the PM_2.5 level was significantly associated with urinary MDA after adjusting for age, sex, BMI, passive smoking, day-care facility site, alcohol consumption, cigarette smoking, and medical history (heart disease, hypertension and bronchial asthma). However, there was no significant relationship for children. Conclusions  The elderly were more susceptible than young children to oxidative stress as a result of ambient exposure to PM_2.5. Identification of oxidative stress induced by PM_2.5 explains the mechanism of adverse health effects such as cardiovascular or respiratory diseases, particularly in the elderly.