In May 2007, Escherichia coli was detected in tap water supplied  by a company in North Holland. The company issued advice through  mass media to boil tap water before consumption; this advice was  lifted six days later. A cross-sectional study was implemented to  investigate compliance among residents in this area. Based on  postcode, a total of 300 households, chosen randomly from a  database of a private company performing internet-based surveys  for different marketing purposes, were sent a self-administered  questionnaire for this study. The questionnaire contained questions  on demographic information, source of information regarding the  advice, response to it and personal opinions on the companys  reaction and the advice. Ninety-nine (66%) households of the  affected area and 90 (60%) households from non-affected areas  served by the same company replied to the survey. All respondents  knew about the advice. 81.8% of the respondents in the affected  area and 5.6% of the non-affected areas reported complying with  the advisory. Most respondents from the affected area still used  unboiled water to brush teeth, wash salads and fruits. There was no  difference in compliance between men and women. Using the mass  media was proved to be efficient to inform the public and could  be used in the future in similar settings. However, more detailed  wording of boiling advices should be considered in the future. Introduction Consumption of drinking water may cause waterborne disease  which can be prevented by protection of the source water, efficient  treatment processes and reliable distribution systems. The  European Union Drinking Water Directive [1] demands monitoring  of tap water for different parameters, such as Escherichia coli, to  indicate possible faecal contamination from humans and animals.  System failure or human error may cause an increase in the  level of pathogens in the water posing a risk of waterborne disease.  For example, in 2001, a large outbreak of gastroenteritis occurred  due to accidental introduction of partially treated water to the  drinking water supply system in the Netherlands, resulting in 921  households being exposed to contaminated water [2]. In the event that faecal contamination is detected the drinking  water company may issue an advice to boil tap water before using  it for domestic purposes. On 15 May 2007, E. coli was detected in  samples collected the day before of the finished tap water delivered  by a company in the province Noord-Holland (North-Holland) in the  Netherlands. For preventive reasons, on the same day the company  issued an advice for consumers to boil tap water for two minutes  before consumption but that this was not necessary for taking a  shower or washing. This information was broadcasted through  mass-media including the national and regional television channel,  radio and newspapers. In addition, a public website used during  emergency situations (www.crisis.nl) and a toll-free telephone  number were made available for the public to provide information  to households in the affected area. The boil water advice had an impact on approximately 180,000  households in the affected area comprising 13 municipalities.  The advice was lifted a week later, on 22 May 2007, as risk for  public health was no longer present. In September 2007, the water  company published a press release informing that the cause of the  water contamination was due to run-off of rainwater contaminated  with faeces of breeding gulls on the roof that had seeped into one  of the six storage rooms [3]. Elevated levels of microorganisms in drinking water may  represent a public health risk. For this reason, we investigated  compliance with boil water advice issued by the private water  company following the 2007 incident. Methods A cross-sectional study was implemented to investigate factors  that may have affected water consumption habits of the residents  in the area supplied by the water company. For this purpose, on  the companys behalf, a self-administered questionnaire was sent  to 300 households in June 2007. Households were selected on the  basis of their residence postcodes; half in the area where the advice  was valid and half in areas served by the same company but where  the advice did not apply. These participants were derived from a  database of a private company that conducts online consumer  surveys for marketing purposes.  The questionnaire contained questions on demographic  information, level of urbanisation, source and time of receiving the  information regarding the advice, initial and secondary response to  the advice and personal opinions on the companys response and  the advice itself. The data were sent back to the drinking water  company and the National Institute for Public Health and the  Environment, where they were analysed. The statistical analysis  was done with STATA v10. 2   EUROSURVEILLANCE  Vol. 14  Issue 12  26 March 2009  www.eurosurveillance.org Results Ninety-nine households (66%) from the area affected by water  contamination and 90 households (60%) from control areas  supplied with water by the same company replied to the survey.  Women more often than men responded to the questionnaire  in both the affected and the non-affected areas (57.7% of all  responders). The respondents represented 189 households with a  total population of 505 people, 176 (34.9%) of whom were below  the age of 18 years. There was no statistically significant difference  in the number of children per household between the affected and  the non-affected areas (p=0.112). Descriptive results for the two  different areas are presented in Table 1. All 189 respondents (100%) in both areas answered that  they had been informed about the advice. Ninety-five (50.3%)  of them said they had first heard about it through the television.  Other sources were radio (24.3%), friends, relatives or neighbours  (22.8%), newspapers (19.6%) and the internet (7.4%). Persons living in the affected area were more frequently  disappointed (14.1%) about the choice of the company to use  mass media for the advice than people residing in the non- affected area (2.2%). In the affected area, seven (9.3%) of the  respondents had first reacted with fear to the information on the  possible contamination of water, 34 (45.3%) responded with self- control and 34 (45.3%) with the intention to take measures. The  corresponding percentages for the non affected area were 15.7%,  72.9% and 11.4%. About half (48.5%) of the respondents from the  affected area said they had looked for more information when they  had heard about the advice, while the corresponding proportion of  respondents from the non-affected area was only 8.9% (p<0.001).  The most common source of active search for more information was  the website of the water supply company. Eighty-one (81.8%) of all respondents in the affected area said  they had complied with the advice. This was done by buying bottled  water (43.4% of all respondents in affected area) or boiling tap  water for two minutes before consuming it (70.7%). None of the  respondents in the area stopped consuming tap water completely.  Five (5.6%) of the respondents in the non-affected area were  buying bottled water and three of them (3.3%) were boiling tap  water during the advice. These numbers were considerably lower  than the corresponding ones in the affected area, but showed that  compliance exceeded beyond the affected area. Even though it had not been advised to boil water for activities  such as washing and showering, 26 (26.3%) of the respondents  in the affected area stated that they had not been aware of that. Concerning the image of the drinking water company, 177  respondents (93.7%) thought that the company had done well  informing the consumers about the water contamination and its  response to it. This prevailing opinion was not different between  respondents from the affected area and those from the non affected  area. The respondents compliance with the advice was independent  of sex, age and the presence of children in the household. However,  the respondents were 138.6 times more likely to follow the advice  if a second person in the household was following it as well  (p<0.001). Reasons for non-compliance with the advice are given in Table 2. Some of the respondents replied that they had been using boiled  water for uses other than drinking, too. These results are shown  in Table 3. The majority of the respondents stated that their image of the  company had not changed after the incident and the six-day advice  (78.8% in the affected area and 88.9% in the non-affected area). Factors affecting compliance The type of mass media from which people in the affected  area found out about the advice played no significant role in the  subsequent compliance of the respondents. The highest compliance  rates occurred among those in the affected area who heard about  the advice from the internet (90%) or from friends (89.5%).  Respondents informed by more than one source were more likely  T a b l e  1 Survey on boil water advice in the North Holland province  in the Netherlands, 2007, demographic characteristics of the  respondents Affected area (n=99) Non-affected area (n=90) Total (n=189) p-value Respondents age  (years) 47.7 48.4 48.0 0.7549 Number of people  living in the household 2.62 2.82 2.72 0.2526 Number of children  living in the household 0.78 1.11 0.93 0.0510 T a b l e  2 Reasons for non-compliance with boil water advice in  the affected area in the North Holland province, the  Netherlands, 2007 (n=11) Reason given N % I have enough immunity 1 9.1 The risk was small 1 9.1 I was not worried 3 27.3 It was too much inconvenience 2 18.2 I forgot about it 2 18.2 I had only just found out 2 18.2 Total 11 100.0 T a b l e  3 Use of boiled water for uses other than drinking in the affected area  in the North Holland province, the Netherlands, 2007 (n=99) Domestic use N % To brush teeth 30 28.1 To wash salads 48 35.6 To wash fruits 51 48.4 To make coffee 56 54.7 To make ice cubes 89 87.2 To give to pets 73 69.4     EUROSURVEILLANCE  Vol. 14  Issue 12  26 March 2009  www.eurosurveillance.org  3 to have complied with the advice (90.9% against 79.2%) but  this difference was not statistically significant. The source of  information did not depend on the age (p=0.6532). Compliance  with the advice did not differ between households with children  and those without children (p=0.536). Respondents who undertook active search for more information  may have been more likely to follow the advice than those who did  not proceed to further active search for more information (89.4%  vs. 74.5%, p=0.058). Since all respondents knew about the advice, it was not possible  to estimate unwitting compliance rates. 


What is the source of contamination?
{'answer_id': 263738, 'document_id': 394240, 'question_id': 138456, 'text': 'tap water', 'answer_start': 46, 'answer_category': 'SHORT'}