This study determined the concentrations of lead and cadmium in edible parts of
Colocasia esculenta, Amaranthus spp.and Ipomoea batata cultivated on farms in
industrially polluted sections of Nyabugogo Marsh in Kigali, Rwanda. The
concentrations in all three crops exceeded European Union (EU) standards for metal
concentration in food crops. C. esculenta roots (Taro) contained the highest
concentration of lead (1.02 mg kg-1) and cadmium (0.56 mg kg-1), approximately ten
and six times over the EU limits, respectively. Even though I. batata (sweet potato)
contained the lowest concentrations of lead (0.75 mg kg-1), this is almost eight times
the upper limit. The highest bioaccumulation factors (the ratio of plant metal
concentration to that of the soil in which it is found growing) for both metals were
observed in amaranth plants. The concentrations of lead and cadmium in the farm
soils were all acceptable based on EU standards (300mg kg-1 for lead and 3mg kg-1 respectively.
The average daily consumption by an adult in the community living around the Marsh
and where some of the produce is sold is 50g of amaranth, 120g of taro and 180g of
sweet potato. Based on the metal concentration and these rates of consumption, the
daily dietary intake of lead by an adult in the community from amaranth, taro and
sweet potato is 1 x 10-4, 3 x 10-4 and 4 x 10-4 mg kg-1 respectively. The daily intake of
cadmium is 4 x 10-4, 1.7 x 10-4 and 1.2 x 10-4 mg kg-1 for amaranth, taro and sweet
potato respectively. These metal intakes are well within the recommendations set
forth by the World Health Organisation.
The community also has access to multiple sources of dietary and non dietary zinc
such as beans, milk and rain water collected from zinc coated roofing sheets, which
serves to ameliorate the effects of cadmium. It is however worth noting that survey
data may have yielded overestimates of these zinc sources, due to the conditions
under which the surveys were conducted i.e. in the hearing of neighbors due to the
cramped nature of housing, which may have prompted respondents to inflate
consumption quantities of expensive food items.
The calculated maximum recommended quantities for daily intake of the crops are
very large and are unlikely to be consumed by the population i.e. >2kg of amaranth,
>2 kg of taro and 3 kg of sweet potato per day for an adult. Additionally, because this is a poor community, access to such quantities of food on a daily basis is not likely.
The community is therefore not exposed to health risks from consuming metal
contaminated crops, largely because of the small quantities consumed. The local
population is therefore at no immediate risk to exceeding metal consumption limits by
consuming vegetables grown in the Nyabugogo Marsh, but the threats will likely
increase if the pollution of the Marsh is not addressed.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/10269 |
| Date | 07 July 2011 |
| Creators | Etale, Anita |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf, application/pdf |
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