Investigation of water consumption patterns among Irish adults for waterborne quantitative microbial risk assessment (QMRA)

Microbial and chemical contamination of drinking water supplies can cause human health problems. Microbial pathogens are of primary concern and quantitative microbial risk assessment (QMRA) is employed to assess and manage the risks they pose. Estimates of drinking water consumption, or distributions, are required to assess levels of waterborne pathogen exposure. To establish distributions for the Irish population, water consumption data were collected from 549 rural survey respondents. A further 110 participants completed a five-day water consumption diary. Average daily consumption of tap-water among the primarily rural-dwelling questionnaire respondents was 940 ml day−1 (SD 670 ml day−1) and 1,186 ml day−1 (SD 701 ml day−1) among the principally urban-dwelling diary respondents. Both mean figures are significantly less than the 2,000 ml day−1 default figure currently used for QRMA; therefore its use may lead to overestimation of the waterborne health burden. As the observed daily consumption difference between rural and urban residents is statistically significant, use of separate consumption distributions for QMRA is advocated. Although males reported higher daily tap-water consumption rates than females, these differences were insignificant, so separate consumption distributions are not considered necessary. A log-normal distribution provides the most adequate fit for daily tap-water intake (ml day−1) within both datasets.