Abstract
BackgroundQuantitative Microbial Risk Assessment (QMRA), a modelling approach, is used to assess health risks. Inputs into the QMRA process include data that characterise the intensity, frequency and duration of exposure to risk(s). Data gaps for water exposure assessment include the duration and frequency of urban non-potable (non-drinking) water use. The primary objective of this study was to compare household water usage results obtained using two data collection tools, a computer assisted telephone interview (CATI) and a 7-day water activity diary, in order to assess the effect of different methodological survey approaches on derived exposure estimates. Costs and logistical aspects of each data collection tool were also examined.MethodsA total of 232 households in an Australian dual reticulation scheme (where households are supplied with two grades of water through separate pipe networks) were surveyed about their water usage using both a CATI and a 7-day diary. Householders were questioned about their use of recycled water for toilet flushing, garden watering and other outdoor activities. Householders were also questioned about their water use in the laundry. Agreement between reported CATI and diary water usage responses was assessed.ResultsResults of this study showed that the level of agreement between CATI and diary responses was greater for more frequent water-related activities except toilet flushing and for those activities where standard durations or settings were employed. In addition, this study showed that the unit cost of diary administration was greater than for the CATI, excluding consideration of the initial selection and recruitment steps.ConclusionThis study showed that it is possible to successfully 'remotely' coordinate diary completion providing that adequate instructions are given and that diary recording forms are well designed. In addition, good diary return rates can be achieved using a monetary incentive and the diary format allows for collective recording, rather than an individual's estimation, of household water usage. Accordingly, there is merit in further exploring the use of diaries for collection of water usage information either in combination with a mail out for recruitment, or potentially in the future with Internet-based recruitment (as household Internet uptake increases).
Highlights
Quantitative Microbial Risk Assessment (QMRA), a modelling approach, is used to assess health risks
The objective of this study was to compare household water usage results obtained using two data collection tools, a computer assisted telephone interview (CATI) and a 7-day water activity diary, in order to assess the effect of different methodological survey approaches on results
Timing of the CATI and diaries Administration of CATIs and diaries with the exception of two CATI and seven diaries was compacted into two overlapping periods each of seven weeks duration
Summary
Quantitative Microbial Risk Assessment (QMRA), a modelling approach, is used to assess health risks. Good quality contemporaneous data about the duration and frequency of water-using activities ( in circumstances where water restrictions may be implemented due to water shortages, as is currently the case in many parts of Australia) combined with information about the total volume per exposure event are needed to obtain the total volume exposure per person per annum. This information, in combination with the number of residual micro-organisms present in the source water and the dose response of micro-organism(s), can be used to obtain an estimate of the annual probability of infection associated with micro-organism(s) of concern for designated waterusing scenarios. Knowing the exposure volume per person per annum for a particular water-using scenario (e.g. toilet flushing) and water type, it is possible to determine the minimum level of water treatment necessary to achieve a predetermined health target and/or to determine whether substitution of one water type with another will lead to an unacceptable increase in the magnitude of risk
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