Browsing by Author "Simon, Fides"

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Heavy Metals Contamination in Agricultural Soil and Rice in Tanzania: A Review
(Science Publishing Group, 2016-02-17) Simon, Fides; Mtei, Kelvin; Kimanya, Martin
Heavy metals contamination in agricultural soil is a potential environmental threat to the safety of agricultural food crops such as rice which is consumed by majority of Tanzanians. The aim of this review is to put together available information on sources of heavy metals, their extent of contamination in agricultural soil and in rice, the risk of exposure through rice consumption as well as the relationship between heavy metals contamination in agricultural soils and in rice in Tanzania. There are several methods of determining the concentrations of heavy metals in soils and in rice. These include Inductively Coupled Plasma Mass Spectrometer (ICP – MS) and Energy Dispersive X – ray Fluorescence spectrometer (EDXRF). It has been mostly reported that the extent of heavy metals contamination in agricultural soils is influenced by their closeness to mining or industrial areas. The use of river waters in mining areas or wastewater from industries for irrigation has been associated to increasing levels of heavy metals in agricultural soils. The elevated level of heavy metals in agricultural soils leads to their accumulation in crops especially rice which upon consumption poses health effects to human and the ecosystem at large. This review suggests the need for determining the extent of heavy metals contamination in agricultural soils around potential areas such as mining and to link this with exposure assessment on heavy metals through rice consumption in Tanzania. This information is necessary to establish the extent at which rice consumers in Tanzania are at risk of heavy metals exposure.
Risk of heavy metals exposure through consumption of rice from Kahama and Geita districts
(2016-04) Simon, Fides
Heavy metals exposure is associated with various human health problems. This research aimed at determining the levels of heavy metals in paddy soils and in polished rice from villages around the artisanal gold mining areas in Kahama and Geita districts. It also intended to assess the risk of human exposures of heavy metals through rice consumption around the artisanal gold mining areas in Kahama and Geita districts, Tanzania. Twenty soil samples were collected from paddy fields and 20 polished rice samples grown from those fields were taken from the farmers. An additional 20 polished rice samples were collected from farmers in other villages from the same districts. Information about rice cultivation practices and rice consumption were collected from 40 farmers that were randomly selected, 20 from each of the two districts; Kahama and Geita districts, in which the mining areas are located. Chromium (Cr), copper (Cu), zinc (Zn), Mercury (Hg), cadmium (Cd), nickel (Ni), lead (Pb) and arsenic (As) were determined in the soil and rice samples using Energy Dispersive X–ray Florescence spectrometer. Heavy metals exposure through rice consumption, for each of the forty farmers, was determined using deterministic approach. In all the soil samples, concentrations of Cd and Cr were found to be above the maximum limits of 1 mg/kg and 100 mg/kg, respectively, as set by Tanzania Bureau of Standards (TBS). Concentrations of Pb and Cd in all the rice samples were above the maximum limits set by Codex Alimentarius Commission. Forty percent of the farmers consumed rice at least once daily with per capita consumption of 66.8 g per day for Geita district and 74.0 g per day for Kahama district. According to Joint FAO/WHO Expert Committee on Food Additives (JECFA), the estimated daily intake (EDI) for Cd was found to be above tolerable daily intake (TDI) for 95% of all population in both Kahama and Geita districts while the estimated daily intakes (EDIs) for As, Zn and Cu in both Kahama and Geita population were below the TDIs. The results also showed that sites which are closer to the mining activities had higher heavy metal concentration in both rice and soils compared to the sites further away from the mining activity.