title: Quantifying tap-to-household water quality deterioration in urban communities in Vellore, India: The impact of spatial assumptions.
abstract: Municipal water sources in India have been found to be highly contaminated, with further water quality deterioration occurring during household storage. Quantifying water quality deterioration requires knowledge about the exact source tap and length of water storage at the household, which is not usually known. This study presents a methodology to link source and household stored water, and explores the effects of spatial assumptions on the association between tap-to-household water quality deterioration and enteric infections in two semi-urban slums of Vellore, India. To determine a possible water source for each household sample, we paired household and tap samples collected on the same day using three spatial approaches implemented in GIS: minimum Euclidean distance; minimum network distance; and inverse network-distance weighted average. Logistic and Poisson regression models were used to determine associations between water quality deterioration and household-level characteristics, and between diarrheal cases and water quality deterioration. On average, 60% of households had higher fecal coliform concentrations in household samples than at source taps. Only the weighted average approach detected a higher risk of water quality deterioration for households that do not purify water and that have animals in the home (RR=1.50 [1.03, 2.18], p=0.033); and showed that households with water quality deterioration were more likely to report diarrheal cases (OR=3.08 [1.21, 8.18], p=0.02). Studies to assess contamination between source and household are rare due to methodological challenges and high costs associated with collecting paired samples. Our study demonstrated it is possible to derive useful spatial links between samples post hoc; and that the pairing approach affects the conclusions related to associations between enteric infections and water quality deterioration.
authors: Department of Civil & Environmental Engineering, Tufts University, Medford, MA, USA.
authors: Tania M
authors: TM
authors: Alarcon Falconi
authors: Department of Civil & Environmental Engineering, Tufts University, Medford, MA, USA.
authors: Alexandra V
authors: AV
authors: Kulinkina
authors: Department of Community Health, Christian Medical College, Vellore, Tamil Nadu, India.
authors: Venkata Raghava
authors: VR
authors: Mohan
authors: Division of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India.
authors: Mark R
authors: MR
authors: Francis
authors: Division of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India.
authors: Deepthi
authors: D
authors: Kattula
authors: Division of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India.
authors: Rajiv
authors: R
authors: Sarkar
authors: Division of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India; Department of Geographic Medicine, Tufts Medical Center, Boston, MA, USA.
authors: Honorine
authors: H
authors: Ward
authors: Division of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India.
authors: Gagandeep
authors: G
authors: Kang
authors: Department of Community Health, Christian Medical College, Vellore, Tamil Nadu, India.
authors: Vinohar
authors: V
authors: Balraj
authors: Department of Civil & Environmental Engineering, Tufts University, Medford, MA, USA; Division of Gastrointestinal Sciences, Christian Medical College, Vellore, Tamil Nadu, India; Friedman School of Nutrition Science & Policy, Tufts University, Boston, MA, USA. Electronic address: elena.naumova@tufts.edu.
authors: Elena N
authors: EN
authors: Naumova
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D002648:Child; D002675:Child, Preschool; D002947:Cities / Q000453:epidemiology; D003967:Diarrhea / Q000453:epidemiology*; D060766:Drinking Water / Q000032:analysis*; D004755:Enterobacteriaceae / Q000302:isolation & purification; D004784:Environmental Monitoring / Q000706:statistics & numerical data; D005191:Family Characteristics; D005243:Feces; D006798:Housing; D006801:Humans; D007194:India / Q000453:epidemiology; D008875:Middle Aged; D016017:Odds Ratio; D012306:Risk; D000068916:Spatial Regression; D014873:Water Pollutants / Q000032:analysis; D060753:Water Quality; D055815:Young Adult
chemical_list: D060766:Drinking Water; D014873:Water Pollutants
keywords: GIS; Household water storage; Spatial modeling; Spatial uncertainty; Water quality; Waterborne diseases