Biomonitoring of Occupational Exposure to Total Arsenic and Total Mercury in Urine of Goldmine Workers in Southwestern Ghana

Abstract

Biomonitoring of total arsenic and total mercury in the urine of goldmine workers in south-western Ghana due to occupational exposure was conducted to determine whether occupational exposure substantially contributes to their overall exposure to arsenic and mercury. The urine was collected after 2-day abstinence from sea foods by the workers and from those with no dental amalgam fillings. Total arsenic and total mercury were simultaneously determined by instrumental neutron activation analysis (INAA). After 1-hour irradiation of the urine in Ghana's miniature neutron source reactor (GHARR-1) to induce ⁷⁶As and ¹⁹⁷Hg radionuclides through nuclear reactions ⁷⁵As(n, γ)⁷⁶As, and ¹⁹⁶Hg(n, γ)¹⁹⁷Hg, the γ-radiation intensity of the induced ⁷⁶As and ¹⁹⁷Hg radionuclides were measured by γ-spectrometry. The validity of the INAA technique for As and Hg determination was checked by analyses of NIST SRM 3103a (As standard solution) and NIST SRM 3133 (Hg standard solution), respectively. The mean mass fractions of arsenic in the urine are 6.76 µg/L ± 1.43, 7.78 µg/L ± 1.33, 8.03 µg/L ± 1.75, 10.44 µg/L ± 1.88, and 14.75 µg/L ± 1.62 for workers in offices 10 km from the mine, 2 km from the mine, 0.5 km from the mine, casual mine workers, and gold ore processing workers, respectively. The levels of arsenic in the urine are all within the 5 to 40 µg As L^-1 day^-1 normal range for excretion of arsenic. The observed mass fraction of As was higher in high exposure workers. The mean mass fraction of Hg in the urine are 0.36 µg/L ± 0.11, 0.47 µg/L ± 0.12, 0.51 µg/L ± 0.16, 0.57 µg/L ± 0.14, and 0.56 µg/L ± 0.21 for workers in offices 10 km from the mine, 2 km from the mine, 0.5 km from the mine, casual mine workers, and gold ore processing workers, respectively. The high Hg exposed workers engage in small scale gold mining using mercury. The exposure of the different categories of workers to both total arsenic and total mercury are safe.