Occupational exposure to dust bound heavy metals and its association with urinary and oxidative stress biomarkers among coal mine workers in Pakistan

Abstract

Coal production is increased tremendously to meet energy requirements. However coal mining activities are becoming serious health concern as these are responsible for the release of various toxic metals enhancing the exposed workers’ vulnerability towards various health implications. There are hardly any studies which have investigated the role of metal exposure causing oxidative stress in coal mine workers. The study aimed to investigate the metal concentration in different particle sizes of dust and its association with urinary metal levels and antioxidant activity as a biomarker of exposure to mining activities. 120 samples of blood and urine were collected from the workers of coal mines of two provinces (Punjab and Balochistan) of Pakistan comprising extractors (n=65), loaders (n=21), managers (n=24). From the same mines 14 dust samples were collected which were later fractionated into three particle sizes (<75um, 75-106um, 106-150um) . Metal analysis was performed by Atomic Absorption Spectroscopy and antioxidant enzymes via UV Spectrophotometer. Among toxic metals Pb (125.5 ± 10.82 mg/kg) and Ni (84.28 ± 7.60 mg/kg) were present in elevated amounts in dust in <75um particle sizes and were also highly enriched in this size fraction with Df of 2.40 and 1.52 respectively. However in case of metal nutrients Mn had increased levels (284.92 ± 17.21 mg/kg). On the contrary macronutrients, like Mg, Na, K had low concentrations in dust but were highly enriched in smallest particle size with Df of 3.88, 2.75, 2.47. The level of urinary metals, high in exposed subjects were Pb (45.07 ± 22.50 ug/g) and Ni (34.60 ± 3.04 ug/g). Among macro and micronutrients Na, K and Zn were observed to have elevated leves of (462.27 ± 15.54 mg/l), (144.47 ± 71.16 mg/l) and (325.71 ± 208.01 ug/g). Except Ca, Fe, and K all other metals had high levels in exposed group as compared to controls and among exposed subjects, extractors had highest mean values for most of the metals. Significantly increased blood MDA levels (84.05 ± 9.96 nm/dl) and reduced SOD (271.54 ±34.18 nm/min/ml) and CAT (135.26 ± 14.44 um/min/ml) activities were observed in exposed workers indicating oxidative stress. The study depicts a strong association ,firstly between metal levels in mine dust and urine of occupationally exposed workers and then between urinary metals levels and antioxidant activities which can cause severe health implications.