Compliance with a boil water advisory after the contamination of a municipal drinking water supply system in Norway

Boil-water advisories (BWAs) are one of the several methods to prevent the spread of infectious diseases through contaminated water. However, for BWAs to be effective, consumers need to be aware of, understand and comply with the advisories. Although BWAs are a widely used preventive public health measure, compliance with BWAs is rarely examined. In Norway, only one previous study on compliance with BWAs has been conducted. Therefore, we conducted a cross-sectional study to estimate consumers ’ perception of and compliance with a BWA following a contamination incident at an elevated reservoir in Konnerud (population 10,314), Norway. In total, 2,451 of the 9,312 (26.3%) invited residents responded to the questionnaire. Among the respondents, 97.6% remembered receiving the BWA, of whom 94.6% complied with the advice. Effective compliance with the BWA was thus 92.3%. Only 130 (5.4%) respondents did not comply with the BWA. The main reason for non-compliance was perceived low or no risk of getting sick from the water (34.2%). Our study revealed high awareness of and compliance with the BWA, but the people who did not comply maintained several misconceptions about waterborne infections and transmission. The ﬁ ndings can be used by local health authorities to improve future BWAs. rarely


INTRODUCTION
water and selected locations on the distribution network, such as elevated water reservoirs, inputs to hospitals and consumers at the end of the supply network (Nygård et al. ; Ercumen et al. ). While issuing BWAs is included in the routine procedures of many water suppliers, a recent study of BWA practices among water suppliers in Norway revealed discrepancies in the number of BWAs issued and procedures used (Kjørsvik & Hyllestad ).
Awareness of gastrointestinal illnesses associated with main breaks and water outages that remain undetected by faecal indicator bacteria have also led to the implementation of precautionary BWAs as a standard practice in several countries, including Norway (Health Canada ; Kjørsvik & Hyllestad ). However, an increase in precautionary BWAs in the future has been discussed in the academic community as a potential dilemma, and the WHO has highlighted the potential negative effects of BWAs, including increased consumer anxiety and scepticism regarding the quality of drinking water, and has advised careful consideration before issuing a BWA (Baird ; WHO ).
On 22 August 2019, a routine water sample taken from an elevated water reservoir located in the Konnerud residential area, part of the drinking water supply system in the Drammen municipality, tested positive for intestinal enterococci. A follow-up sample taken the same day also tested positive for intestinal enterococci. Upon confirmation of the two positive tests, the local health authorities issued a BWA to all the residents of the affected area on 27 August. We conducted a cross-sectional study to examine the perception and compliance by the residents in Konnerud who received the BWA in order to provide recommendations to local health and water authorities regarding the use of BWAs.

Study site
This study was conducted in Konnerud, a residential area in the Drammen municipality in Viken county. Glitre, a lake bordering Drammen and three adjacent municipalities, serves as the raw-water source. The raw water is processed at the Landfall water treatment facility and temporarily stored in a series of elevated reservoirs before entering the municipal distribution network and ultimately reaching consumers.

Study design and population
In October 2019, we conducted a cross-sectional study in Konnerud. We invited all residents aged 16-100 years who received the BWA advice on 27 August to participate.
All residents were registered as customers of the water supplier in the Drammen municipality. The water supplier confirmed the names and addresses via the National Registry, using a geographical information system to identify consumers connected to the affected water supply system.
The main communication mode for the municipality is SMS text messaging (in addition to voice messages). Residents with mobile phone numbers registered in these systems were included in our study. Multiple phone numbers registered to the same household all received an invitation to participate in the study via SMS text messages.

Data collection
Data were collected using a web-based questionnaire, which included questions related to respondents' demographic variables (sex, age and education) and compliance with the BWA or the reasons for non-compliance. We used a Likert-type scale for questions concerning the communication, perception of the BWA, and trust and perception of the drinking water and the responsible water supplier.
The questionnaire was issued in Norwegian 30 days after the incident. The recipients had 14 days to respond, and a feedback reminder was sent 10 days after the initial inquiry. In addition, we collected data on municipality demographics from Statistics Norway, the national statistics institute of Norway, to compare the respondents to the overall population demographics of the municipality.

Data analyses
We compared the demographic data from the whole municipality to the data to those reported by the respondents. We described the sex, age and education of the study population. We calculated the proportion of the respondents who remembered receiving the BWA and complied with the advice in order to calculate the effective compliance rate. Using Pearson's chi-squared test and logistic regression, we determined whether there were differences in compliance in terms of the sex, age and education of the participants. Regarding those who did not comply with the BWA, we described the main reasons for non-compliance.
Using the Likert scale, we determined the communication methods, perception of the BWA, trust and perception of the drinking water quality and the responsible water supplier. We compared the level of trust and the perception of participants who complied and those who did not comply with the BWA using logistic regression. All data analyses were done using STATA/SE 16.0.

Ethical consideration
The study did not require the collection of sensitive information on the study population, and approval from ethical committees was not required. The respondents remained anonymous to the Norwegian Institute of Public Health.

Characteristics of the study population
As of 1 January 2019, Konnerud had 10,314 residents, of which 9,312 fit our inclusion criteria (aged 16-100 years) and were sent an invitation to participate in the study. In total, 26.3% (2,451 individuals) responded to the questionnaire.
Most respondents were female (59%) and significantly younger than the male respondents (50 and 53 years, respectively, p < 0.001). In the Drammen municipality, the mean age of the population at the time of the study was 47 years, with 50.5% being female.
Communication, awareness and compliance with the BWA Among the respondents, 97.6% (2,391) remembered receiving the BWA. The remaining respondents either indicated that they did not receive the advisory (2.0%) or did not recall receiving the advisory (0.5%). Most respondents found the advice 'very easy' or 'easy' to understand (84.9 and 13.4%, respectively). Only a small proportion found the BWA difficult to understand (<1%, 18 people).
Of those who remembered receiving the BWA, 94.6% complied with the advice, resulting in an effective compliance of 92.3% (Table 1). Women were significantly more compliant (97.0%) with the BWA than men (91.1%; p < 0.001). No statistically significant associations were found between compliance and age or education.
Despite being aware of the BWA, 117 (4.9%) respondents did not comply, and 13 (0.5%) did not remember complying. For those who indicated that they did not comply, the reasons for non-compliance can be found in Table 2.

Perception and trust
The water quality in the Drammen municipality was assessed to be 'good/very good' by 91.4% of the respondents and 'bad/very bad' by <1% (20 people). Most of the participants (88.3%) were 'not worried/not very worried' about contracting disease via tap water, with only 5.1% (127) of the respondents stating they were 'worried/very worried.' In response to the community's ability to handle similar incidents in a safe manner, the majority (91.3%) of the respondents had 'high/very high' confidence and few (1.8%) had 'low/very low' confidence. Following the BWA distribution, 9.2% of the respondents experienced decreased trust in water quality, while the majority (56.1%) reported an increase of trust. The rest stated that the BWA had no influence on their trust (33.4%) or that they were uncertain (1.4%). Water quality and confidence in the community's ability to handle the situation were significantly associated with lower compliance (Table 3).

DISCUSSION
The present study reported on public compliance with a   Grover ).
Differences in the demographic profile, including gender and age, were observed between the respondents and the municipality. Like the studies in the meta-analysis, our study revealed a skewed gender distribution, with the majority being female (59%). If and how this might have influenced our study is unknown, but our study revealed that women were more likely to comply with the BWA than men. The true compliance could, therefore, be lower than estimated by our study. We did not consider the difference in mean age (3 years) to represent a significant impact on the representativeness of the study. The difference in mean age (three years) was not considered to have a significant impact on the representativeness of the study.
Despite being aware of the BWA, a small proportion of the respondents chose not to comply with the recommendations. To improve compliance rates further and minimise potential health risks, it is crucial to understand the reasons for non-compliance. In our study, we found that the main reasons for not complying with the BWA were primarily linked to a low perception of risk. Other reasons given for non-compliance (Table 2)

Perceived trust
Trust in water quality following BWAs may differ between countries but also within countries. The WHO states that BWAs can have substantial adverse consequences and that frequent and prolonged advisories may decrease compliance (WHO ). In our study, more than half of the respondents described increased trust in the water quality following a BWA, one-third of the respondents were unaffected, and a small number of the respondents lost trust.

CONCLUSIONS
The results of our study on the perception of, and compliance with the BWA in Konnerud demonstrated that the water supplier was highly successful in communicating the BWA in an understandable manner. Albeit a small proportion, non-compliance did exist and was primarily linked to a lack of perceived risk and misconceptions about the transmission of waterborne illness. Based on these findings, we suggest that future BWAs address these issues directly in the advisory by including targeted information about specific risks. To reduce potential confusion among communities regarding BWAs and maintain a high level of trust by the consumers, we also believe that a uniform set of guidelines and regulations concerning BWAs should be considered.
Our study expands the knowledge of a scarcely studied topic in public health. Continued population growth, an aging water supply system and prospects of more extreme weather are all factors that might fatigue the water supply infrastructure in the future and increase the risk of water contamination. An increase in precautionary BWAs and emergency BWAs following more severe contamination incidents should, therefore, be planned for. We recommend continued research and monitoring of compliance with BWAs.