Bandara et al. 2010 — Dietary cadmium and endemic chronic renal failure in Sri Lanka
An endemic form of chronic renal failure (CRF) emerged in 2002 in the North Central Province of Sri Lanka, concentrated among lowland rice farmers. This study identifies elevated dietary cadmium from triple superphosphate (TSP) fertilizer as the source, with cadmium contamination accumulating through irrigation water, soils, and staple foods including rice, fish, and pulses. The authors estimate dietary cadmium intake between 15–28 µg/kg body weight per week, far exceeding WHO guidelines, and link this exposure pattern directly to the CRF epidemic affecting rural farming communities.
Key numbers
Dietary cadmium intake (PTWI equivalents):
- Estimated weekly intake: 15–28 µg/kg body weight per week (vs WHO PTWI: 0.007 µg/kg bw)
- Infants fed breast milk from exposed mothers: 48.72 µg/kg bw per week
- Ages 4–5 with typical meals: 20.701 µg/kg bw per week
- Adults with typical meals: 5.988–6.319 µg/kg bw per week
Urinary cadmium (biomarker):
- Stage 5 CRF patients (Anuradhapura): 7.58 ± 6.18 µg Cd/g creatinine
- Stage 5 CRF patients (Polonnaruwa): 5.65 ± 5.46 µg Cd/g creatinine
- Asymptomatic persons: 11.6 µg/g creatinine (abstract)
Cadmium in food items (µg/kg ww basis, from Table 3):
- Rice: range 1.7–92.5 µg/kg, mean 23.356 ± 22.877 µg/kg
- Pulses (Vigna radiata): range 2.1–99.2 µg/kg, mean 31.774 ± 28.047 µg/kg
- Tilapia fish: range 0.5–90.7 µg/kg, mean 21.763 µg/kg
- Lula fish (Channa striata): range 1.2–114.4 µg/kg, mean 20.243 ± 71.548 µg/kg
- Lotus rhizomes: range 2.3–271.3 µg/kg, mean 46.407 µg/kg
- Foliar vegetables: range 1.6–96.5 µg/kg, mean 23.795 ± 29.415 µg/kg
- Breast milk: range 0.52–75.32 µg/l, mean 18.235 ± 20.74 µg/l
- Cow milk: range 0.12–84.48 µg/l, mean 14.01 ± 20.90 µg/l
- Buffalo milk: range 57.1–82.28 µg/l, mean 69.63 ± 14.15 µg/l
Cadmium in drinking water and reservoirs (from Tables 1–2):
- Dissolved cadmium in reservoir waters: 0.03–0.06 mg/l (10–20× WHO MCL of 0.003 mg/l)
- Irrigation/reservoir water from homes: 0.08–29.14 µg/l, geometric mean 3.174 µg/l
- Shallow wells: 0.205–187 µg/l, geometric mean 6.931 µg/l
- Agro wells: 2.72–38.8 µg/l, geometric mean 11.18 µg/l
- Pipe-borne water: 0.88–10.38 µg/l, geometric mean 2.274 µg/l
- Tube wells: 1.7–33.66 µg/l, geometric mean 3.852 µg/l
Cadmium source — TSP fertilizer and soils:
- TSP fertilizer cadmium content: 23.5–71.7 mg/kg (mean 47 mg/kg)
- Soil cadmium (Anuradhapura district): uncultivated 0.02 ± 0.01 mg/kg vs cultivated 0.11 ± 0.19 mg/kg
- Soil cadmium (Polonnaruwa district): uncultivated 0.005 ± 0.004 mg/kg vs cultivated 0.016 ± 0.005 mg/kg
- Reservoir sediment cadmium: 1.8–2.4 mg/kg dry weight
- Cadmium transfer from Upper Mahaweli diversion: 72.13 kg/day
Fertilizer use and cumulative cadmium input:
- 1970: 32,000 metric tons fertilizer used
- 1975: 74,000 metric tons (>2.3× increase)
- Estimated total cadmium input to rice-cascade environment since 1973: up to 68.9 metric tons
Methods
Analyzed cadmium in food, water, soil, and urine from CRF-affected and non-affected populations in Sri Lanka’s North Central Province. Food items (rice, pulses, fish, vegetables, lotus rhizomes, milk) collected from CRF patients’ homes (n=30 samples per site for some analyses). Drinking water and irrigation water samples (n=50) analyzed from households of confirmed CRF patients across Anuradhapura, Madawachchiya, Polonnaruwa, and Medirigiriya. Soil samples from cultivated and uncultivated land. Cadmium determined by graphite furnace atomic absorption spectrometry (GF-AAS); detection limit 0.015 µg/l. Dietary intake calculated by food frequency and typical meal composition. Urinary cadmium used as biomarker of long-term exposure.
Implications
This is a landmark epidemiological study establishing elevated dietary cadmium as the source of an endemic chronic renal failure epidemic in Sri Lanka. The data are directly relevant to HMT&C limits for cadmium in rice, infant formula (via breast milk), and other staple foods consumed in South Asia. The study demonstrates that cumulative cadmium exposure from agricultural fertilizer can produce population-level renal disease at dietary intakes far below current international regulatory thresholds. The evidence base supports precautionary cadmium limits in rice-consuming populations and strengthens the rationale for tighter HMT&C certification standards in infant formulas and weaning foods to protect vulnerable age groups already exposed through breast milk.
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