H2S as an indicator of water supply vulnerability and health risk in low-resource settings: a prospective cohort study - PubMed (original) (raw)

H2S as an indicator of water supply vulnerability and health risk in low-resource settings: a prospective cohort study

Ranjiv S Khush et al. Am J Trop Med Hyg. 2013 Aug.

Abstract

In this large-scale longitudinal study conducted in rural Southern India, we compared a presence/absence hydrogen sulfide (H2S) test with quantitative assays for total coliforms and Escherichia coli as measures of water quality, health risk, and water supply vulnerability to microbial contamination. None of the three indicators showed a significant association with child diarrhea. The presence of H2S in a water sample was associated with higher levels of total coliform species that may have included E. coli but that were not restricted to E. coli. In addition, we observed a strong relationship between the percent positive H2S test results and total coliform levels among water source samples (R(2) = 0.87). The consistent relationships between H2S and total coliform levels indicate that presence/absence of H2S tests provide a cost-effective option for assessing both the vulnerability of water supplies to microbial contamination and the results of water quality management and risk mitigation efforts.

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Figures

Figure 1.

Figure 1.

Village-level mean water quality indicators in village source and household samples. Total coliforms (top panel) and H2S (bottom panel). Arrows between points indicate the direction of change between household sample means and village sample means. N = 3,026 household samples; N = 695 village source samples.

Figure 2.

Figure 2.

Percent positive H2S tests by total coliform concentration for household and village source samples. Vertical lines are robust 95% confidence intervals. Asterisks (*) mark statistically different means between household and village source samples at the 95% confidence level. N = 3,026 household samples; N = 695 village source samples.

Figure 3.

Figure 3.

Relationship between the percentage of H2S positive tests and log10 total coliform concentration for village source samples (left) and household samples (right) using mean concentrations at the village level. N = 695 village source samples; N = 3,026 household samples. The fitted line in the village source samples is a weighted least squares fit with parameters H2S = −92.9 + 51.0 × log10TC, R2 = 0.87. The parameters fit including both village (left) and household samples (right) was similar: H2S = −90.2 + 51.3 × log10TC, R2 = 0.81, and the fit was not greatly improved using a logistic instead of linear model.

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