This cross-sectional survey measured iron and manganese in 85 working tubewells in Jashore district that had previously been marked safe for arsenic. Most wells exceeded the Bangladesh drinking-water limits for both metals, and the authors used United States Environmental Protection Agency hazard-quotient arithmetic to screen adult and child intake from drinking water. The paper is direct drinking-water occurrence evidence for iron, with a modeled rather than measured health dimension.
Key numbers
- Tubewell iron ranged from 0.02 to 6.2 mg/L, median 0.69 mg/L, interquartile range 0.27 to 2.47 mg/L, n = 85 (Results, p. 4; Fig. 2).
- Mean iron was 1.4 mg/L, which the authors describe as 4.6 times the iron limit (Results, p. 4).
- Category counts: 23 wells (27%) below 0.3 mg/L (mean 0.14 mg/L); 38 wells (45%) from 0.3 to 2.0 mg/L (mean 0.75 mg/L); 24 wells (28%) above 2.0 mg/L (mean 3.72 mg/L, maximum 6.20 mg/L) (Table 1, p. 3).
- About 73% of wells exceeded the iron limit for Bangladesh drinking water (Abstract; Results, p. 4).
- Reference values used by the paper: WHO aesthetic value 0.3 mg/L for iron; Bangladesh standard 0.3 to 1.0 mg/L for iron; a 2.0 mg/L “JECFA” cut-off derived by allocating 10% of a provisional maximum tolerable daily intake of 0.8 mg/kg body weight to drinking water (60 kg, 2 L/day); oral reference dose 0.7 mg/kg/day attributed to a 2006 US EPA provisional value (pp. 1 to 3).
- Exposure assumptions: 3.53 L/day and 50 kg for adults, 1.0 L/day and 15 kg for children (Methods, p. 4).
- Iron hazard quotient for adults: 0.004 to 1.446, median 0.161; above 1 in about 8% of wells (n = 7). Children: 0.002 to 0.590, median 0.066, none above 1 (Results, p. 6; Fig. 6).
- Iron plus manganese hazard index above 1 at 33 wells (about 39%) for adults and at three wells for children (p. 7; Fig. 7).
- Detection range of the iron method: 0.02 to 3.0 mg/L (Methods, p. 2).
Methods (brief)
One heavily used public tubewell per union (85 of 93 unions; eight waterlogged unions excluded) was pumped for 5 to 8 minutes, sampled into acidified polyethylene bottles, filtered (1.0 µm glass microfiber) and analyzed for iron by the FerroVer colorimetric method on a spectrophotometer, with blank and replicate samples. Spatial maps used inverse distance weighting. Arsenic was not re-measured.
Evidence fitness
Supports statements about total (filtered) iron concentrations in rural Bangladeshi drinking-water wells, their spatial spread, and how often they exceed the cited water values. The hazard quotients are screening arithmetic resting on assumed intake and body weight and on a reference dose the paper attributes to another document; they are not measured health outcomes. The authors themselves state that the elevated levels could represent a potential risk that cannot be established with certainty, in part because bioavailability was not measured.
Limitations
Dry-season sampling only, one well per union, no temporal replication, and a colorimetric method whose stated range tops out near the higher values reported. Filtration before analysis means particulate iron was excluded. The text gives two different arsenic cut-offs for the “safe” well marking (0.05 mg/L in Methods and 0.005 mg/L in Limitations). The paper also labels the “high” spatial class as “>0.2 mg/L” in one sentence, which conflicts with the 2.0 mg/L class boundary used elsewhere.
Related evidence
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