Cu content of all the samples in three tested areas below the safe limit. As shown in Fig 2 reasonably high Cu content was observed in Turkey berry, Spade leaf, Chinese spinach, and Jewels of opar at Puhudivula and Ungas Wewa. However, the safe limit set for Cu (40 mg/kg) is well above the observed values (One-Way ANOVA, p<0.05). Hence, harm caused to Human beings due to Cu is negligible.
Cr content of Jewels of opar, Spade leaf, and Turkey berry in all three tested areas and Chinese spinach in Unagas Wewa exceed the safe limit for Cr (Fig 3). Cr content of Chinese spinach in Mahadiwul Wewa and Puhudivula and that of Mango in Mahadiwul Wewa and Unagas Wewa were closer to the safe limit. Cr content of Papaya in all three sites was also closer to the safe limit (One-Way ANOVA, p<0.05). However, literature evidence reports that elevated Cr levels in food cause no considerable damage to Kidney (
Wilbur et al., 2012).
The highest level of Pb content which exceeds the safe limit was observed in Jewel opar at Mahadiwul Wewa. Apart from that Pb content in Chinese spinach of all 3 sites was higher and very close to the safe limit. Spade leaf of Mahadiwul Wewa and Puhudivula and Jewel of opar at Puhudivula also showed elevated Pb content, nearly closer to the safe limit. However, Pb content of turkey berries in Puhudivula is somewhat lower than the Pb content of turkey berries in Mahadivul Wewa and Uangas Wewa (Fig 4). Pb content of Papaya and Mango in all three sites was also not considerably higher (One-Way ANOVA, p<0.05).
As indicated in Fig 5 Chinese spinach, Jewels of Opar, Spade leaf, and Turkey berry samples in three tested areas were heavily contaminated with Cd exceeding the safe limit set by WHO. Cd content of papaya and mango was below the safe limit (One-Way ANOVA, p<0.05). Mango is a bigger tree with many branches. Absorbed Pb could be distributed all over the tree. Mango fruit is a very small part when compared with the size of the tree. Hence, a small portion of absorbed Pb would be seen in the fruit. Papaya is also a somewhat bigger plant concerning the other plants selected in the study. Papaya fruit is also smaller than the tree. Hence only a portion of absorbed Pb could be seen in the fruit.
All these findings revealed that tender leafy vegetables that grow as small plants were heavily contaminated with tested heavy metals Pb, Cr, and Cd. Turkey berry, a fruity vegetable of the small shrub-like plant also been contaminated to a considerable level. Of these contaminants, Cr cause no considerable damage to Kidney (
Wilbur et al., 2012).
Mahadiwul Wewa, Puhudiwula, and Unagas Wewa selected in the present study were located, within a 100 m area of three reservoirs, which are used for farming.
Bandara et al. (2008) also claimed elevated Cd and Pb levels in the soil at a 50 m area of another two reservoirs in Medawachchiya. In agreement with Bandara’s work, in the present study higher-level Cd and Pb, which exceed WHO limit, were detected in leafy and fruity vegetables grown within a 100 m area of above three reservoirs located in CKDu-prone Medawachchiya. As reported in
Bandara et al. (2009) average Cd level in cultivated vs. uncultivated soils in Medawachchiya, has been recorded as 0.02±0.01 vs. 0.11±0.19 mg/kg. As indicated by them Cd pollution has occurred through contaminated phosphate fertilizers and pesticides used in agriculture. Cd level of Triple superphosphate (TSP) fertilizer has been reported as 23.5-71.7mg /kg.
Chandrajith et al. (2009) also reported that the application of fertilizer in the long run led to a significant level of accumulation of Cd and Pb in agricultural soil in NCP. Compared with other heavy metals, Cd tends to be more mobile in the soil, can easily enter from soil to plant, and accumulate in cultivated crops and vegetables (
Curtis and Smith, 2002).
Bandara et al. (2009) also revealed that most human exposure to Cd occurs due to high levels of dietary Cd which comes through agriculture. Provisional tolerable weekly intake for Cd at all ages for rice, pulses, fish, breast milk, and cow’s milk has exceeded the safe level recommended by
Codex (2009).
Acien et al. (2009) also revealed that renal dysfunction can often be caused due to chronic exposure to Cd. Renal tubular damage caused due to Cd is known to be irreversible. Chronic exposure to Pb is reported to cause hematological, cardiovascular, neurological and progressive tubulointerstitial nephropathy that leads to kidney failure (
Acien et al., 2009).
Based on the survey we conducted, 19, 13 and 7 CKDu patients were recorded at Mahadiwul Wewa, Puhudivula and Unagas Wewa respectively. Of all the patients, 12 had both diabetes and hypertension. Ten had diabetes. Seven had hypertension. Others had no diabetes or hypertension. Supporting the above evidence
Young et al. (2015) also suggested that Cd is a possible contributor to the prevalence of CKD and exerts a detrimental effect on the kidneys in diabetic or hypertensive patients (
Young et al., 2015). Even at low Cd levels, chronic Cd exposure can lead to renal damage, particularly in patients who suffer from diabetes or hypertension (
Akesson et al., 2005). This risk may contribute to a synergic effect in the development and progression of CKD. Consequently, diabetic or hypertensive subjects become more susceptible to the diseased condition.
Bandara et al. (2008) also noted high levels of Cd pollution in water, freshwater fish, their staple diet rice and other food items such as milk and vegetables. Further, they pointed out that the existence of a high level of fluoride in ground water which is used as drinking water increases Cd absorption through the gastrointestinal tract as fluoride compounds. Apart from that, Cd absorption through the human gastrointestinal tract has been reported to increase, in the subject with low proteins and iron status (
Bandar et al. 2008). Pre-school children (1-4 years) in the NCP are under-nourished and underweight with a Z score of 0.208 (
Rathnayake and Weerahewa, 2005). Those children at a very young age are also highly vulnerable to the current crisis in the NCP.
As pointed out by
Bandara et al. (2008), if the situation doesn’t reverse human dietary Cd exposure continuously to increase, the diseased condition will be more prevalent in the next few decades, especially in high-risk groups with diabetes, hypertension, and those undernourished in protein and iron.
