Eau potable et santé publique : défis actuels et futurs Drinking water and public health: present and future challenges

Résumé

L’eau que nous consommons chaque jour est essentielle à la vie. Sa qualité a toujours été un élément indispensable à un environnement favorable à la santé. Actuellement, loin d’avoir été résolu, le problème de la qualité de l’eau de boisson est toujours une priorité de santé publique, autant dans les pays en voie de développement que dans les pays industrialisés.

Ce texte présente six défis pour la santé publique dans le dossier de l’eau potable pour les années futures :

1. L’utilisation d’une approche multibarrière dans la production et la distribution de l’eau potable, qui inclut la protection des sources d’eau, l’utilisation d’un traitement efficace, la qualité du réseau de distribution, la surveillance de la qualité de l’eau et la réponse lors d’un problème;

2. La mise au point de meilleures normes de qualité d’eau par le choix d’indicateurs plus pertinents, l’utilisation de méthodes d’analyse de risque plus adaptées, le suivi de la qualité de l’eau plus fréquent à être fait au robinet du consommateur;

3. L’amélioration de la surveillance des maladies d’origine hydrique ainsi que des méthodes d’investigation des épidémies;

4. L’amélioration des liens avec la communauté;

5. La prise en compte de critères de gestion transparents qui incluent l’accessibilité, l’équité, et les analyses coûts-bénéfices;

6. Le développement de la recherche sur les maladies d’origine hydrique, en particulier sur l’exposition réelle des populations aux contaminants de l’eau et l’évaluation des effets de la contamination de l’eau sur la santé.

Finalement, le problème de la qualité de l’eau potable doit être appréhendé dans une perspective mondiale.

Mots clés:

• Eau potable,
• santé,
• normes,
• surveillance,
• gestion des risques

Summary

Drinking water is essential to human life. Drinking water quality has always been an essential component of a healthy environment. In fact, the risk of waterborne diseases, either from microbiological or chemical contamination of drinking water, is still ubiquitous in both industrialized and non-industrialized countries. Recently, several outbreaks of waterborne enteritis in North America have confirmed the presence of this risk, with some potentially dramatic consequences such as the case that occurred in Walkerton, Ontario. Vulnerable people such as infants, pregnant women, senior citizens and individuals with compromised immune systems are particularly at risk. Other factors such as travel, migration, climate change, and intensive agriculture might increase the risk of emerging diseases. The lack of basic measures of public health such as protection of sources of water, adequate water treatment, or surveillance of drinking water has also been underlined in recent epidemics. Multi-chemical contamination at very low doses by pharmaceuticals or disinfectant by-products is also an issue that public health practitioners must deal with. New technology enables us to detect chemicals that were not detectable a few years ago.

With respect to all these potential threats, this paper presents six major challenges in the area of drinking water that are considered by the author as a priority for public health:

1. Implementation of the multi-barrier approach is fundamental for the prevention of waterborne diseases. It includes the protection of drinking water sources from contamination, efficient water treatment in every community including those in remote areas, operation and maintenance with competent operators, good water quality within the entire distribution network, an adequate monitoring of drinking water using real-time surveillance when feasible, and finally, rapid responses to «red flags» which might be raised by all types of monitoring and surveillance.

2. Increasing the level of drinking water standards is also paramount. It includes the use of the most pertinent index of bacterial, viral and parasitic contamination during water monitoring. This is also true for chemicals, where a global index of health risk should be developed. The use of the best risk-assessment methods when deriving standards is recommended, especially regarding the consideration of exposure through inhalation and dermal contact and the vulnerability of some sub-populations. An increase in the frequency of water quality monitoring is also recommended with sampling, when necessary, at the consumer’s tap.

3. Improving waterborne disease surveillance and methods of detection and investigation of outbreaks are still important. These are the public health watchdogs that are very useful when the previous measures have failed. They include the use of rapid and easy means of surveillance of acute enteric symptoms, such as monitoring diarrhoea medication sales, telephone calls received at a Health Line, or the monitoring of diarrhoea in some at-risk populations. Up-to-date methods to track pathogens in outbreak investigations would also be very useful to link diseases to water contamination.

4. Enhancing the links with communities is an important component of public health intervention. It includes annual reports to communities on water quality and involving citizens at the beginning of discussions when all important decisions regarding drinking water have to be made (e.g., upgrading a treatment plant). It might also be possible to inform a community when contaminants are found with concentrations that exceed 50% or less of the water quality standards.

5. Use of transparent and fair management criteria is a critical issue. Several standards have been driven mostly by the technical limitations of analytical methods and a low-cost approach. There are also potential threats that some minorities could have less access to water of good quality and suffer the burden of water contamination. The new management should include some important criteria as equity, social solidarity and valid cost-benefit analysis.

6. Developing research into human exposure and waterborne diseases epidemiology is the key issue to derive new knowledge to come up with the best water quality standards. It includes the use of efficient epidemiologic designs and a special focus on vulnerable populations (e.g., pregnant women, infants). Toxicological studies might still be useful if they improve risk assessment.

In conclusion, beyond traditional methods that have to be updated (multi-barriers, quality standards and surveillance of waterborne diseases and investigation of outbreaks), the new components of the public health approach in drinking water are: the quality of the link with the community, the use of transparent and fair criteria for risk management, and a strong research agenda focussing on human health impacts. Finally, the use of a global perspective is paramount. Most drinking water issues are spread worldwide and cooperation between nations and countries is an important component of a healthy world in this twenty-first century.

Key words:

• Drinking water,
• health,
• standards,
• surveillance,
• risk management