Mercuric pollution of surface water, superficial sediments, Nile tilapia (Oreochromis nilotica Linnaeus 1758 [Cichlidae]) and yams (Dioscorea alata) in auriferous areas of Namukombe stream, Syanyonja, Busia, Uganda

Abstract

The mercury content and the contamination characteristics of water, sediments, edible muscles of a non-piscivorous fish (Oreochromis nilotica Linnaeus 1758 [Cichlidae]) and yams (Dioscorea alata) from Namukombe stream in Busia gold district of Uganda were evaluated. Human health risk assessment from consumption of contaminated fish and yams as well as contact with contaminated sediments from the stream were performed. Forty-eight (48) samples of water (n = 12), sediments (n = 12), fish (n = 12) and yams (n = 12) were taken at intervals of 10 m from three gold recovery sites located at up, middle and down sluices of the stream and analyzed for total mercury (THg) using US EPA method 1631. Results (presented as means ± standard deviations) showed that water in the stream is polluted with mercury in the range of < detection limit to 1.21 ± 0.040 mg/L while sediments contain mean THg from < detection limit to 0.14 ± 0.040 ugg−1. Mean THg content of the edible muscles of O. nilotica ranged from < detection limit to 0.11 ± 0.014 ugg−1while D. alata contained from < detection limit to 0.30 ± 0.173 ugg−1mean THg. The estimated daily intake ranged from 0.0049 ugg−1day−1 to 0.0183 ugg−1day−1 and 0.0200 ugg−1day−1 to 0.0730 ugg−1day−1 for fish consumed by adults and children respectively. The corresponding health risk indices ranged from 0.0123 to 0.0458 and 0.0500 to 0.1830. Estimated daily intake was from 0.0042 ugg−1day−1 to 0.1279 ugg−1day−1 and 0.0130 ugg−1day−1 to 0.3940 ugg−1day−1 for D. alata consumed by adults and children respectively. The health risk indices recorded were from 0.011 to 0.320 and 0.033 to 0.985 for adults and children respectively. The mean THg content of the sediments, edible muscles of O. nilotica and D. alata were within acceptable WHO/US EPA limits. About 91.7% of the water samples had mean THg above US EPA maximum permissible limit for mercury in drinking water. Consumption of D. alata grown within 5 m radius up sluice of Namukombe stream may pose deleterious health risks as reflected by the health risk index of 0.985 being very close to one. From the pollution and risk assessments, mercury use should be delimited in Syanyonja artisanal gold mining areas. A solution to abolish mercury-based gold mining in the area needs to be sought as soon as possible to avert the accentuating health, economic and ecological disaster arising from the continuous discharge of mercury into the surrounding areas. Other mercury-free gold recovering methods such as use of borax, sluice boxes and direct panning should be encouraged. Waste management system for contaminated wastewater, used mercury bottles and tailings should be centralized.

Heavy metals in soils and edible tissues of Lepidium meyenii (maca) and health risk assessment in areas influenced by mining activity in the Central region of Peru

“…The higher EDI, HQ and HI values for children than adults is due to the differences in the ingestion rates of food contaminated with heavy metals, body weights as well as the exposure times [ [101] , [102] , [103] ]. Overall, no potential health risk for both children and adults was found.…”

Effects of alkali treatment on the mechanical and thermal properties of sisal/cattail polyester commingled composites

“…Paired t test was performed to identify any significant differences between groups. All analyses were performed at a 95% confidence interval (with differences in mean values accepted as being significant at p < 0.05) using Sigma Plot statistical software (v14.0, Systat Software Inc., San Jose, CA, USA) (Omara et al, 2019).…”

“…Equipment such as pH meter and analytical balance were calibrated prior to use. All samples were analyzed at least in triplicate to obtain a relative uncertainty of less than 5% (Omara et al, 2019).…”

Health Risks from Intake and Contact with Toxic Metal-Contaminated Water from Pager River, Uganda

“…For human health risks associated with PTEs, the assessment is performed by taking into consideration the potential cancer and non-cancer health effects in adults (“as the general population”) and children (“as a sensitive group”). For non-carcinogenic health risks, the average daily doses are computed to cater for the direct intake of water (DIT water ) and dermal contact (DC water ) (Equations (1) and (2)) [ 43 , 44 ]. where PTEC = PTE ’s concentration in water (mg/L); W IG (water intake rate; L/day) = 1.8 and 21 for children and adults; E FQ = exposure frequency (365 days/year); E DT = exposure time, equal to the average lifetime (58.65 years) for Ugandans [ 44 , 45 ]; W B = average body weight (=15 kg for children and 60 kg for adults); T AE = average exposure time, expressed as E FQ × E DT [ 46 ]; SAF is the exposed dermal surface area = 2800 and 24,350 cm 2 for children and adults [ 43 ]; DAFC is the dermal absorption factor = 0.01 for carcinogenic metals [ 47 ]; and SADF is the skin adherence factor = 0.2 and 0.7 mg/cm 2 /day for children and adults [ 48 ].…”

“…To assess non-carcinogenic health risks, the target hazard quotient (THQ) is calculated (Equations (3) and (4)). In consequence, THQ ≤ 1 shows unlikely occurrence of adverse health effects in an exposed individual and vice versa [ 44 , 48 ]. Because such effects are augmentative for PTEs, the cumulative health risks per exposure pathway (total THQ DIT water and total THQ DC water ) may be calculated (Equations (5) and (6)) [ 30 ].…”