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A survey of tap water consumption patterns amongst under 16s - WT1255

1. Background

The setting of standards and guideline values for drinking water rests on knowledge of the quantities of tap-water that people actually drink. Information on intakes is equally important when making risk assessments.

Surveys of tap water consumption have been conducted in 19781, 19952 and most recently in 20083. This most recent study, the national of tap water consumption survey for England and Wales, provides robust data on the consumption patterns of tap water amongst the adult population (defined as 16 and over). The report covers different types of drinks (eg tea, coffee, water, squash) and quantified the variations in average consumption between genders, weights, age-bands, socio-economic groups and regions. Habits of water usage were also studied. However the survey excluded consumption by under 16 year olds.

The 1995 survey included about 201 children from a total sample size of 1031 individuals. The 2008 sample was larger, approx 1500 individuals in each seasonal wave but did not include any children under 16. The 1978 survey was larger again including 3,564 individuals of which 842 were under 15 year of age and 962 were under 18. The 1995 survey gave average intakes for the age groups 0-5 and 6 - 15. It did not give any indication of the variation in consumption within these group, though the distribution of consumption within the whole sample size was reported. The 1978 study reported average intakes and 10 and 90 percentiles for each gender and each of three age groups 1- 4, 5-11 and 12-17. Again the distribution across the sample as a whole was reported.

For certain parameters, especially lead, children are a particularly sensitive group of the population, therefore it is important to have accurate tap water intake estimates for children. The total or average volume drunk may not be the most useful measure when estimating the lead intake. This is because the concentration of lead within a sample of water is dependent on many factors, two of the most important are whether the plumbing is made of lead and how long the water has been standing in the pipes before the drink was drawn. So a more useful measure may be how much first draw water from properties with lead pipes is consumed.

The 2008 and 1995 surveys only looked at the issue of first draw of water in a relatively simple way by asking whether drawing water for a drink was the first use of the day. Less than a third of household 1995 and a quarter in 2008 described drawing water for drinks as the first use of the day.

The 1978 study provides more detailed data assigning water to three categories: first draw; random; or flushed. Only 4% of the water consumed was described as first draw, 12% as flushed and 82% as random. An earlier study4 as part of the British Regional Heart Study gave a similar result, it indicated only 6% of the volume consumed could be described as first draw, though there were differences in the volumes described as flushed (37%) and random (57%)

In order to conduct a microbiological risk assessment it is also important to understand how much of the volume consumed was “un-boiled”. This is because the boiled component will not provide a microbiological risk.

The 2008 survey looked for the first time at consumption using sports bottles, it may be that this consumption route is particularly important for children.

2. Purpose

The purpose of this research project is to provide accurate estimate of tap water and total liquid intake by children under 16 years of age, including the distribution of the volume drunk.
The objectives are to:

• provide a robust estimate of the average total daily tap water consumption by children in England and Wales and the proportion of total daily liquid consumption that this represents, and to detect whether there has been a change in average consumption of tap-water based drinks since previous surveys that included children. Details of sample sizes of previous surveys are given above. Tenderers are required to indicate the level of robustness that would be achieved by a range of different sample sizes, with different costings, and power analyses (estimated 95% confidence intervals at least)

• describe the distribution of intakes across the sample and provide estimates of intakes for extreme consumers (for example 95 percentile intakes) Tenderers are required to indicate the level of robustness of these extreme intakes that would be achieved by a range of different sample sizes, with different costings, and power analyses (estimated 95% confidence intervals at least)

• provide robust estimates of intake (both average and extreme) and distribution data for each different form of tap water eg boiled vs unboiled, direct from the tap vs filled bottles and first draw vs flushed and random daytime consumption. It is recognised that extreme estimates may be less robust than average estimates. Tenders must estimate sample size, response rate and design effect of their weighting strategy and hence the approx level of accuracy the survey would support at a 95% confidence level.

• provide reliable information on differences in consumption patterns across age sub groups, gender, weight, region and socio economic groups. Different costed sample sizes should be given, stating how much disaggregation each would allow and how robust the results would be.

• estimate the relative significance of tap water substitutes consumed, with particular attention to bottled water

• Comment on the significance of any trends or changes observed and discuss possible reasons for them.

Project Documents
• FRP - Final Report : DWI70 2 251   (1665k)
• EXE - Executive Summary : DWI70 2 251exsum   (73k)
• OTH - Other : DWI70 2 251 diaries   (2288k)
Time-Scale and Cost
From: 2010

To: 2011

Cost: £70,050
Contractor / Funded Organisations
Drinking Water              
Fields of Study
Water Quality