The use of town refuse ash in urban agriculture around Jos, Nigeria: health and environmental risks

• Published in: The Science of the total environment Vol. 354; no. 1; pp. 43 - 59
• Main Author: Pasquini, M.W.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 15.01.2006; Elsevier Science
• Subjects: Agriculture - methods; Agronomy. Soil science and plant productions; Air. Soil. Water. Waste. Feeding; Applied sciences; Biological and medical sciences; Cities; Crops, Agricultural - chemistry; Daucus carota - chemistry; Environment. Living conditions; Environmental Monitoring; Exact sciences and technology; Fertilizers; Food Chain; Food Contamination; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Global environmental pollution; Heavy metals; Incineration; Jos Plateau; Lactuca - chemistry; Medical sciences; Metals, Heavy - analysis; Nigeria; Other nutrients. Amendments. Solid and liquid wastes. Sludges and slurries; Pollution; Public health. Hygiene; Public health. Hygiene-occupational medicine; Risk Assessment; Soil Pollutants - analysis; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Town refuse ash; Vegetable crops; Nigeria; Africa; Nigeria, Plateau, Jos; Jos Plateau; Town refuse ash; Heavy metals; Vegetable crops; Fertilization; Pollutant behavior; Urban waste; Agricultural soil; Soil pollution; Heavy metal; Waste management; Trophic chain; Health and environment; Vegetable crop; Upgrading; Ash; Surface water; Health hazards; Waste reuse; Agriculture; Stream; Water pollution; Soil plant relation; Public health
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2004.12.025

This paper reports on a study that examines the health and environmental risks of using town refuse ash in urban vegetable production in Jos, Nigeria, in terms of heavy metal accumulation in the food chain. Soil and crop samples, collected from five study farms, and samples of the river water used for irrigation, were analysed for seven heavy metals Fe, Mn, Zn, Cu, Ni, Cd and Pb. On the basis of the field data the paper discusses: (1) the potential soil deficiencies and toxicities; (2) the probable links between soil heavy metal levels and fertilisation practices; (3) the heavy metal concentrations in crop tissue in relation to crop growth and human health. The findings suggest that soil concentrations of the seven metals fall within ‘typical’ soil levels, and that there should not be any problems of either toxicities or deficiencies for crop growth. There was evidence of slight accumulation of Zn, Cu and Cd on some of the farms with a history of town refuse ash use. However, in all farms lettuce crops contained very large concentrations of Fe, and Pb concentrations that were 20 to 40 times higher than the WHO/FAO maximum recommended level in leafy vegetables for human consumption. The Cd content of carrot tissue was 10 times higher than the WHO/FAO recommended limit. The relatively small number of soil and crop samples precluded any formal attempt at correlating the concentrations of heavy metals found in the vegetable crops with the farm levels. Nevertheless, the data suggested that these were not linked. The paper goes on to consider various potential sources of the metals found in the crops, including irrigation water, town refuse ash and air-borne dust, and discusses additional health and environmental risks pertaining to the use of town refuse ash. Undoubtedly, the heavy Pb and Cd contamination of certain crops indicates the urgent need for future studies to ascertain the precise source of these metals, and although the practice of using town refuse ash does not appear to have resulted in large-scale contamination of soil in the farming area, there are a number of unsafe practices associated with it that call for the identification of strategies for the safe utilisation of urban waste in Jos.