Academic journal article Environmental Health Perspectives

Exposures to Particulate Matter and Polycyclic Aromatic Hydrocarbons and Oxidative Stress in Schoolchildren

Academic journal article Environmental Health Perspectives

Exposures to Particulate Matter and Polycyclic Aromatic Hydrocarbons and Oxidative Stress in Schoolchildren

Article excerpt

BACKGROUND: Air pollution is known to contribute to respiratory and cardiovascular mortality and morbidity. Oxidative stress has been suggested as one of the main mechanisms for these effects on health.

OBJECTIVE: The aim of this study was to analyze the effects of exposure to particulate matter (PM) with aerodynamic diameters [less than or equal to] 10 [micro]m ([PM.sub.10]) and [less than or equal to] 2.5 [micro]m ([PM.sub.2.5]) and polycyclic aromatic hydrocarbons (PAHs) on urinary malondialdehyde (MDA) levels in schoolchildren.

METHODS: The study population consisted of 120 schoolchildren. The survey and measurements were conducted in four cities--two in China (Ala Shan and Beijing) and two in Korea (Jeju and Seoul)--between 4 and 9 June 2007. We measured daily ambient levels of PM and their metal components at the selected schools during the study period. We also measured urinary 1-hydroxypyrene (1-OHP) and 2-naphthol, to assess PAH exposure, and MDA, to assess oxidative stress. Measurements were conducted once a day for 5 consecutive days. We constructed a linear mixed model after adjusting for individual variables to estimate the effects of PM and PAH on oxidative stress.

RESULTS: We found statistically significant increases in urinary MDA levels with ambient PM concentrations from the current day to the 2 previous days (p < 0.0001). Urinary 1-OHP level also showed a positive association with urinary MDA level, which was statistically significant with or without PM in the model (p < 0.05). Outdoor PM and urinary 1-OHP were synergistically associated with urinary MDA levels. Some metals bound to [PM.sub.10] (aluminum, iron, strontium, magnesium, silicon, arsenic, barium, zinc, copper, and cadmium) and [PM.sub.2.5] (magnesium, iron, strontium, arsenic, cadmium, zinc, aluminum, mercury, barium, and copper) also had significant associations with urinary MDA level.

CONCLUSION: Exposure to PM air pollution and PAHs was associated with oxidative stress in schoolchildren.

KEYWORDS: children, metal, oxidative stress, PAH, panel study, particulate matter. Environ Health Perspect 118:579-583 (2010). doi:10.1289/ehp.0901077 [Online 14 December 2009]

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Air pollution has been found to contribute to respiratory and cardiovascular morbidity and mortality, including asthma, myocardial infarction, stroke, and cancer (de Kok et al. 2006; Hong et al. 2002; Schwartz and Morris 1995). Although many epidemiologic studies have consistently shown the damaging health effects of air pollution, there are critical gaps in understanding the mechanism of such effects. Some animal studies have shown a pathogenetic linkage between exposure to air pollutants and health effects; however, evidence for human health is still limited (Moller et al. 2008).

Oxidative stress is known to be induced by air pollution in animal studies (Kodavanti et al. 2001), and epidemiologic studies conducted in urban areas have also demonstrated that oxidative stress was associated with environmental air pollutants in bus drivers (Rossner et al. 2008a). Oxidative stress is thought to be caused by redox-cycling organic chemicals and transition metals bound to the surface of particulate matter (PM) and produced by enzymatically catalyzed reactions in target cells. In general, PM with aerodynamic diameters [less than or equal to] 2.5 [micro]m ([PM.sub.2.5]) has been observed to be more toxic than PM with aerodynamic diameters [less than or equal to] 10 [micro]m ([PM.sub.10]) for the same unit increase in concentration, presumably with more chemicals bound to the particles (de Kok et al. 2006; Xia et al. 2006). Despite these findings, our understanding is still limited on whether PM air pollution causes oxidative stress in children.

Oxidative stress is defined as an impaired balance between free radical production and antioxidant capacity resulting in excess oxidative products (Hong et al. …

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