Occupational exposure to heavy metals (Cd, Co, Zn) associated with DNA oxidative stress: a cross-sectional study among urban green space workers; Tehran, Iran

Abstract

heavy metals impact the urban population, the environment, and workers exposed to these pollutants. Green space workers during the day shift and peak city traffic hours have constant exposure to air pollutants. This study aimed to determine the concentration of heavy metals including, Cd, Co, and Zn in urine and breathing air samples among green space workers of Tehran Municipality and investigate the associations between heavy metal exposure and DNA oxidative stress. In addition, a comparative analysis was conducted between green space workers and office employees (as the control group). NIOSH-7300 and NIOSH-8310 were used to collect and prepare air and urine samples. The final sample concentration was measured by ICP-OES. Furthermore, two 96-test ZellBio GmbH kits assessed urinary 8-OHDG, a biomarker of DNA oxidative stress. The mean concentration of urinary and air heavy metals and urinary 8-OHDG exhibited a statistically significant increase in the exposed group compared to the control group (except for Cd in the air). Moreover, the Pearson correlation coefficient (R) between urinary heavy metals and 8-OHDG values in the exposed group revealed that there are significant relations between urinary Cd, Co, and Zn with 8-OHDG: R = 0.734, R = 0.836, and R = 0.584 respectively (P˂0.001). No correlations were observed between heavy metals and 8-OHDG in the control group. Findings revealed that cobalt and cadmium exhibit the most significant influence on changes in oxidative stress, as indicated by the dependent variable 8-OHDG. This study showed a strong association between exposure to heavy metals and 8-OHDG levels in workers with low airborne metal exposure, however, future studies should also recognize the indisputable role of heavy metals in oxidative stress and examine other factors like diet, lifestyle, habits (smoking and exercising), and other pollutants in affected workers' environment.