Pollution of River Mahaweli and farmlands under irrigation by cadmium from agricultural inputs leading to a chronic renal failure epidemic among farmers in NCP, Sri Lanka

Abstract

Chronic renal failure (CRF) associated with elevated dietary cadmium (Cd) among farming communities in the irrigated agricultural area under the River Mahaweli diversion scheme has reached a significantly higher level of 9,000 patients. Cadmium, derived from contaminated phosphate fertilizer, in irrigation water finds its way into reservoirs, and finally to food, causing chronic renal failure among consumers. Water samples of River Mahaweli and its tributaries in the upper catchment were analyzed to assess the total cadmium contamination of river water and the possible source of cadmium. Except a single tributary (Ulapane Stream, 3.9 μg Cd/l), all other tested tributaries carried more than 5 μg Cd/l, the maximum concentration level accepted to be safe in drinking water. Seven medium-sized streams carrying surface runoff from tea estates had 5.1-10 μg Cd/l. Twenty larger tributaries (Oya), where the catchment is under vegetable and home garden cultivation, carried 10.1-15 μg Cd/l. Nine other major tributaries had extremely high levels of Cd, reaching 20 μg Cd/l. Using geographic information system (GIS), the area in the catchment of each tributary was studied. The specific cropping system in each watershed was determined. The total cadmium loading from each crop area was estimated using the rates and types of phosphate fertilizer used by the respective farmers and the amount of cadmium contained in each type of fertilizer used. Eppawala rock phosphate (ERP), which is mostly used in tea estates, caused least pollution. The amount of cadmium in tributaries had a significant positive correlation with the cadmium loading of the cropping system. Dimbula Tea Estate Stream had the lowest Cd loading (495.9 g/ha/year), compared with vegetable-growing areas in Uma Oya catchment with 50,852.5 g Cd/ha/year. Kendall's τ rank correlation value of total Cd loading from the catchment by phosphate fertilizer used in all crops in the catchment to the Cd content in the tributaries was +0.48. This indicated a major contribution by the cropping system in the upper catchment area of River Mahaweli to the eventual Cd pollution of river water. Low soil pH (4.5-5.2), higher organic matter content (2-3%), and 18-20 cmol/kg cation exchange capacity (CEC) in upcountry soil have a cumulative effect in the easy release of Cd from soil with the heavy surface runoff in the upcountry wet zone. In view of the existing water conveyance system from upcountry to reservoirs in North Central Province (NCP) through diversion of River Mahaweli, in addition to their own nonpoint pollution by triple superphosphate fertilizer (TSP), this demands a change in overall upper catchment management to minimize Cd pollution through agriculture inputs to prevent CRF due to elevated dietary cadmium among NCP farmers.

Escalating chronic kidney diseases of multi-factorial origin in Sri Lanka: causes, solutions, and recommendations

“…Some researchers have suggested an association between the prevalence of CKD-mfo and the cascade irrigation systems [2], particularly the diverted water from the Mahaweli River [37] in Sri Lanka. However, other scientists have disputed this and failed to confirm these findings [2,3].…”

“…Since the initiation of this programme, which included newer fast-flowing hydraulic technologies, from an environmental point of view, things have worsened [37,102,104,105]. It is plausible that this acceleration of irrigation project and human settlements have contributed to the current CKD-mfo epidemic [37], but there is no direct evidence. Nevertheless, this project negatively affected the fauna, flora, and human health in the region; the areas where water is now supplied by the diverted Mahaweli River water.…”

Water quality of Nilwala River, Sri Lanka in relation to land use practices

“…Similarly, excess fertilizer which is contaminating the river from upstream land use practices such as agricultural activities may have also contributed to this situation. Several researchers have reported the impact of agriculture on the quality of irrigation and potable water in Sri Lanka (Amarasekara 1992; Bandara et al 2008;Bandara et al 2011). Application of excessive quantities of nitrates and phosphates are associated with eutrophication of reservoirs and heavy nitrate levels in reservoirs and ground water in Sri Lanka (Weeraratne and Wimalawansa 2015).…”

Oxidative Stress and Cardiovascular Dysfunction Associated with Cadmium Exposure: Beneficial Effects of Curcumin and Tetrahydrocurcumin

“…Osteoporosis and nephropathy caused by Cd exposure were found in populations living in polluted areas of southeast China (Jin et al 2004). A high prevalence of renal failure was also detected among the farmers in the agricultural area under irrigation in the North Central Province, Sri Lanka (Bandara et al 2011). Chronic Cd toxicity is a significant health concern among workers engaged in zinc smelting, battery production and silver jewellery industries, particularly in developing countries.…”