The mercuric content, pollution and contamination characteristics of water, sediments, edible muscles of a non-piscivorous fish (Oreochromis nilotica Linnaeus 1758 [Cichlidae]) and yams (Dioscorea alata) in mercury-based artisanal and small-scale gold mining (ASGM) impacted Namukombe stream and its propinquity, Busia gold district, Uganda were evaluated. Human health risk assessment from consumption of the fishes and yams as well as dermal contact with sediments from the stream were performed. Forty-eight (48) samples of water (12), sediments (12), fish (12), and yams (12) were taken at intervals of 0, 10, 20 and 30m from up, middle and down sluices of the stream and analyzed for total mercury (THg) using US EPA method 1631. Results showed that water in the stream is polluted with mercury (Hg) in the range of 0.00 to 1.21±0.070mg/L while sediments contain Hg up to 0.14±0.04ugg-1. THg content of the edible muscles of Oreochromis nilotica ranges from 0.00 to 0.11±0.010ugg-1 while yams contain 0.00 to 0.30±0.001ugg-1 of Hg. The estimated daily intakes (EDIs) ranged from 0.0049 to 0.0183ugg-1day-1 and 0.020 to 0.073ugg-1day-1 for fish consumed by adults and children respectively. The corresponding health risk indices (HRIs) ranged from 0.0123 to 0.04576 and 0.05 to 0.183. EDIs were from 0.0042 to 0.1279ugg-1day-1 and 0.013 to 0.394ugg-1day-1 for yams consumed by adults and children respectively. The HRIs recorded were from 0.011 to 0.320 and to 0.033 to 0.985. All the mean THg contents of the investigated matrices were within acceptable WHO/US EPA limits except for water samples. Consumption of yams grown at 0m up sluice of Namukombe stream may pose deleterious health risks as reflected by the HRI of 0.985 being very close to 1.0. From pollution and risk assessments, Hg usage should be delimited in Syanyonja ASGM areas; solutions to abolish mercury based ASGM in the area ought to be sought at its soonest to avert the accentuating health, economic and ecological disaster arising from the continual discharge of Hg into the surrounding areas. Other safe gold recovery methods such as use of borax should be encouraged. Waste management system for contaminated wastewater, used Hg bottles and tailings should be centralized to enable Hg waste management in ASGM areas in Syanyonja.

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.

Syanyonja village in the gold district of Busia, South East of the Republic of Uganda contain geologically epigenetic gold quartz vein deposits in carbonate-altered mafic metavolcanic rocks, deposited as quartz reefs in mineralized shear zones. In supracrustal rocks, alluvial gold is obtained from weathered auriferous quartz veins, which are of late orogenic granitic activity. The Syanyonja gold deposits have long been subjected to artisanal and small-scale gold mining (ASGM) by the locals for livelihood. This study determined the amount of mercury discharged with tailings into Namukombe stream, a major water body in Syanyonja village and investigated the impacts of ASGM on the mining population and the environment. Quantitation of mercury discharged with tailings was done by mass balance method. Field survey at the mining sites was done followed by administration of questionnaires to 50 stampeders in the village. The study indicates that about 8% of mercury mixed with auriferous materials are lost in tailings, accounting for an annual mercury release of about 1.757 kg into the environment. Socio-demographic results indicate that the majority of the mining population (64%) are male and ASGM have left health and environmental footprints, which directly or indirectly affects the population. The most common health problems among miners are malaria (36%) and abdominal pain (20%). The standard of living of the miners are evidently low, and most mines are characterized by school dropouts, prostitutes and thieves. Mining sites have deplorably poor hygiene, with evident burning of amalgams to recover gold. ASGM have been accompanied by wanton mowing down of vegetation, land degradation as well as mercuric pollution of water, air, land and aquatic ecosystems. It is suggested that the Ugandan government should re-enforce committees to follow up on ASGM activities, train artisans on sustainable gold mining using borax, magnets, sluice boxes as well as take up farming actively as an alternative.

The mercuric content, pollution and contamination characteristics of water, sediments, edible muscles of a non-piscivorous fish (Oreochromis nilotica Linnaeus 1758 [Cichlidae]) and yams (Dioscorea alata) in mercury-based artisanal and small-scale gold mining (ASGM) impacted Namukombe stream and its propinquity, Busia gold district, Uganda were evaluated. Human health risk assessment from consumption of the fishes and yams as well as dermal contact with sediments from the stream were performed. Forty-eight (48) samples of water (12), sediments (12), fish (12), and yams (12) were taken at intervals of 0, 10, 20 and 30m from up, middle and down sluices of the stream and analyzed for total mercury (THg) using US EPA method 1631. Results showed that water in the stream is polluted with mercury (Hg) in the range of 0.00 to 1.21±0.070mg/L while sediments contain Hg up to 0.14±0.04ugg-1. THg content of the edible muscles of Oreochromis nilotica ranges from 0.00 to 0.11±0.010ugg-1 while yams contain 0.00 to 0.30±0.001ugg-1 of Hg. The estimated daily intakes (EDIs) ranged from 0.0049 to 0.0183ugg-1day-1 and 0.020 to 0.073ugg-1day-1 for fish consumed by adults and children respectively. The corresponding health risk indices (HRIs) ranged from 0.0123 to 0.04576 and 0.05 to 0.183. EDIs were from 0.0042 to 0.1279ugg-1day-1 and 0.013 to 0.394ugg-1day-1 for yams consumed by adults and children respectively. The HRIs recorded were from 0.011 to 0.320 and to 0.033 to 0.985. All the mean THg contents of the investigated matrices were within acceptable WHO/US EPA limits except for water samples. Consumption of yams grown at 0m up sluice of Namukombe stream may pose deleterious health risks as reflected by the HRI of 0.985 being very close to 1.0. From pollution and risk assessments, Hg usage should be delimited in Syanyonja ASGM areas; solutions to abolish mercury based ASGM in the area ought to be sought at its soonest to avert the accentuating health, economic and ecological disaster arising from the continual discharge of Hg into the surrounding areas. Other safe gold recovery methods such as use of borax should be encouraged. Waste management system for contaminated wastewater, used Hg bottles and tailings should be centralized to enable Hg waste management in ASGM areas in Syanyonja.

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