Associations between oxidative stress levels and total duration of engagement in jobs with exposure to fly ash among workers at municipal solid waste incinerators

The fly ash from municipal solid waste incinerators (MSWIs) is known to contain heavy metals, polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polyaromatic hydrocarbons (PAHs), and other organic materials. Heavy metals, PCDDs, PCDFs and PAHs reportedly cause oxidative stress in vitro and in vivo. In this study, we have measured the blood and urinary levels of several oxidative stress markers in MSWI workers and discuss herein whether the duration of engagement in jobs with exposure to MSWI fly ash is associated with these levels. The subjects were 81 male workers (mean age 42.7 years) from four MSWIs in the same city. Job history was determined from each subject and jobs were categorized according to the possibility of exposure to fly ash. The subjects were classified into four groups: long duration of engagement in jobs with exposure to fly ash, short duration of engagement in jobs with exposure to fly ash, engagement in jobs with limited exposure to fly ash and control. Blood and urine specimens were obtained from the subjects in the morning before breakfast. The levels of 8-hydroxy-2'-deoxy-guanosine (8-OH-dG) in the urine and leukocytes were measured as markers of oxidative DNA damage. Blood malondialdehyde and lipid peroxide levels and the level of total urinary biopyrrins were also measured as markers of systemic oxidative stress. The mean levels of all markers were compared among the four groups. There was a significant trend showing that the level of urinary 8-OH-dG rose with increased duration of engagement in jobs with exposure to MSWI fly ash (P < 0.05). Considering this result, we speculate that certain chemicals in fly ash might have induced oxidative stress in the study subjects.