Application of the Population Health Approach to Drinking Water System Surveillance

环境与职业医学2007年2月第24卷第1期J Environ Oecup Med, Feb 2007 VoL.24 No.1117 .Aricle ID:00-36172001-0117-03CLC Number:R12Document:A[Information ]Application of the Population Health Approach to DrinkingWater System SurvillanceWeimin Hu, Deborah Kelly Barnard, Esther Parker, Ann ThomasKey Words: drinking water; sureillance; british columbia; canadaA drinking water supply is a complicated system in its1 Data and Methodologyconstruction, operation, maintenance and need for public health1.1 The Populationi Health Approachsurvillance. The role of public health in a drinking water supply isThe Population Health Approach was proposed by Healhto ensure public health protection in all public and community waterCanada in 20013]. As depicted in Figure 1, this approachsystens from intake to tap by contolling and preventing outbreaksemphasizes that the health of a population is determined by orof infectious diseases, inspecting and monitoring water systems,associated with a variety of factors. The population, rather than the. licensing operating permits, and regulating the construction,individual, is the base unit for the study of health, This approachalternation or extension of all public and community water systems' 'provides a conceptual framework for health surveillance.British Columbia Drinking W ater Protection Act (DWPA)and regulations came into force on May 16, 2003121. The provincehas increased basic expectations regarding: the assessment ofwater systems, the certification of operators and suppliers, and thePopulaeionMulipleHealh ShahusBasomonitoring and reporting of water quality.GOALSlamprovebeatTo meet the new legislative requirements, it is essential forVIHA to understand each of the existing water systems that supplies. eterentioontorgctonalstants inequitiesDeterminendrinking water to the public. For every system, its source of water,ofHelhpurveyor, distribution network, and consumers (population) allAnlyis oHeatl bsessneed to be fully documented and incorporated into an informationsystem. Most importantly, drinking water quality information and。口Pptio Heat Key Bess口Gmrie roes Soeresurvillance have to address risks to the health of the population.Therefore, the population characteristics, including demographic*Population and Public Health Branch. The population population healthfeatures, health status, and socio- economic conditions, all needapproach, July 2001. Otuawa, ON: Strategic Policy Directorate, Healthto be incorporated into water system survillance. This clearlyCanada.indicates that a comprehensive system that integrates both waterFigure 1 The Population Health Approach*systems and population health information is essential. Based onthis understanding, the Publie Health Survillance Unit (PHSU) of1.2 Health Geographical Information System (HGIS)the Authority decided to incorporate water sureillance as a moduleThe framework of the Population Health Approach suggestsof its comprehensive health geographical information system tothat the study of population health needs to take multiple sources ofassist in meeting the legislative requirements for drinking waterinformation into account. In addition, the information cannot simplysurvillance.be piled together; rather it needs to be integrated in a meaningfulway. The HGIS, developed by the PHSU as a comprehensive, healthspati中国煤化工Phieal inomation syslem(GIS)muliple kinds of health-Weimin Hu, MB MSc PhD, Population Health Epidemiologist,relateYHC N M H G, scioconomie, helth,Population Health Survillance Unit, Office of the Chief Medicaland disease statistics. Geography or location is used here as theHealth Officer, South Island, Vancouver Island Health Authority,linkage point to integrate all the information together.l*lAs one ofthe many dimensions of the health of a population, drinking waterVictoria, British Columbia, Canada●118●环境与职业医学2007年2月第24卷第1期J Environ Occup Med, Feb 2007 Vol.24 No.1quality and surveillance should logically be integrated into this stree type, and a range of addresses that occur along each streetsystem so that the ssues related to drinking water will be consideredsegment) on a map. During the geocoding process, an address of ajointly with other determinants of population health. This is thewater system is matched to a corresponding address in the streetconceptual structure of the population health perspective on drinkingreference theme. Once the correct location has been assigned to anwater surveillance (Figure 2).address, a location identifier is given map coordinates and becomesa permanent geocode. This process is the computer equivalent ofpushing pins into a street map on a wll'l.With GIS, each watersystem, by means of the geocoding process, is spatially enabled andDrinking. Water●Distributiongeographically located on a map.Health EventSpatial2 ResultsReferenceLand Use2.1 Inventory of Drinking Water Systemsand Synthesis .Census DataAccording to HealthSpace, there are 828 water systems onVancouver Island (not including private water systems with onlyone connection). These systems serve populations ranging from twohouseholds to over 300.000 people. They are categorized by size,Compositeaccording to the number of connections or users served. The greaterthe number of connections, the larger the population served by theFigure 2 Drinking water and health GIS: information integration andwater system[6] (see Table 1). The‘'public" or“ munieipal”water systems supply drinking water to the majority of the population,comprehensive analysisalthough they are fewer compared to other types. However, it is the“small”types of water systems that draw the atention of public13 Spatial and Attribute Informationhealth survillnce. Due to the relatively small number of consumersOne of the advantages of PHSU's HGIS is that it is built onbut the larger number of systems, it is a challenge for the program toexisting data sources, rather than needing to rely on new surveys.do routine inspections, especially as most of the systems are locatedThe spatial data, which have spatial coordinates and can be locatedin rural and remote areas.geographically on a map, mainly come from Statistics Canada'scensus geographies, and they include polygons of enumerationTable 1 Drinking water system types(or dissemination) areas, census tracts and census divisions, andDrinking water 6ystem typeCapecity (mumber of cnections)postal codes. In addition, boundaries of local health authorities andDWP“publie"> 20.000street network files are purchased. The attribute information, whichDWM "municeipal"10.001 to 20.00includes descriptions of the characteristics of each spatial entity, isDWT“Iown"301 to 1.0000from sources similar to Statistics Canada's census datasets; it comes15 to300from locally maintained population and neighborhood databases.These attributes are spatially linked to relevant geographies,DWS“*maul"2to 14constructing a profile of each of the geographical feature.DWQ“quasi"1 (pubiHealthSpace, an information system supporting theWH "hauler"Water haulerEnvironmental Health Protection Program, collects facility andinspection information for health protection and environmental2.2 Spatial Distribution of Water Systems by Health Serviceservices. The fcility data are olleted for food premises, tobaco Delivery Area (HSDA)retailers, daycare facilities, swimming pools and drinking waterThe distribution of all water system is mapped by differentsystems. The information on drinking water systems collected byHealth Services Delivery Area (HSDA). Relatively speaking, forHealthSpace is the starting point for this project. The data elementsinstance, South Island is an urbanized and populated region withwill be reviewed and data quality will be assed. The gaps betweena number of urban centers like Victoria, Oak Bay, Saanich, andavailable and needed information on each water system will berural and remote region like Salt Spring Island. The distribution ofidentifed.the water systems within these regions shows a clear patter that1.4 Geocoding Techniques in Water Systems Mappinglargerr water systems, those with more than 300 connections, areUnderstanding where a water system is located is the firstconcentr中国煤化工- maller systems are inquestion for this study. Identification of each water systemrural andgeographically enables a linkage between the water system and the2.3 LinMYHc N M H Ger Supply Systemconsumers (publie). A special technique with GIS, geocoding, isTo link a water system to its source is to associate the source ofused to pinpoint every water system, based on its street address andthe water system to the distibution area. Such linkage enables onestreet reference theme (with attributes that specify the street name,to establish an association between water supply and water source..环境与职业医学2007年2月第24卷第1期J Eniron 0ccup Med, Feb 2007 Vol.24 No.1.119●From a population health perspective, this association is important inlater phases will be conducted in order to improve the accuracy ofwater quality monitoring. Mapping both water system and watershed geocoding process.can further ilustratle this relationship.3.3 Moving Forward2.4 Linkage between Water Supply and the PopulationUntil recently, no map of water distribution systems withinFrom the population health perspective, water systemVIHA existed. Using GIS software and the process known assurveillance should be carried out in the context of populationgeocoding, the distribution of known and documented systemshealth. Therefore, it is essential to link the water supply systemthroughout VIHA have now been mapped. As result of this work,to the population whc actually co1 sume the wa er. Such linkageVIHA is taking the above mentioned steps to improve the accuracyenables a path to be traced from a population or community, whereand completeness of the data in HealthSpace. The informationa waterbore disease occurs, to the water system supplying drinkingsystem will be further developed to add an inventory of risk factorswater to the community. Currently, our information systems have notrelated to water systems and their sources, including land use,been able to establish such linkages. However, this study furtherindustrial activities and other human activities that can impact onsuggests the necessity of such linkages. It has been planned thatwater quality. Improved data quality will result in enhanced publicthe later phases of this study will spatially link the geography of thehealth protection and improved reporting capability. By using adistribution area for each water system to the population.GIS, for example, a large amount of data about disease organismoutbreaks or the presence of contaminants in public water systems3 Discussioncould be analyzed and displayed spatially- -perhaps revealingThis article introduces a conceptual framework of a systematicunexpected patterns related to land use that might not be detectedand sustainable drinking water surveillance system from theotherwise.perspective of population health. This is a muli-phase project. Theresults presented here are only a part of the findings from the first Reference:phase. The primary goal of phase I is to gather information to support[ 1 ]Brish Columbia Provincial Health Officer. A report on the healthVIHA's drinking water program development. The three majorof British Columbians. Provincial Health 0fficer's annual reportachievements of the Phase I study include developing an inventory2000. Drinking waler quality in Brtish Columbia: The publie healthof drinking water systems within VIHA, spatially enabling the dataperspective[ R ]. Victoria, B. C: Ministry of Health Planning, 2001.using a GIS, and identifying gaps in the data required for the system.[ 2 Bitih Columbia Government. Drinking Water Proeetion Act, S.B.CSome of the issues and challenges derived from this early phase[S], 2001,c.9.study are briely summarized below.[ 3 ]Population and Publie Health Branch. The populaion heilth template:3.1 Challenge with Datakey elements and actins that define a population health approach[ R ].The address used to map a water distribution system was theOtawa, ON: Strategic Policy Directorate, Health Canada, 2001."facility location adress" field from HealthSpace. Unfortunately, [ 4 ]HU w, BARNARD K D. Comprehensive Healh Geographiethis address has had a number of diferent definitions. Inaccurate orInformation System (HCIS) in Population Health Practice[C]. St.incomplete address information is not the only problem that VIHAJohn's, Newfoundland, Canada: Presentation at the Canadian Publiefaces with its water system data. VIHA has begun a concertedHealth Association (CPHA) 95th Annual Conference, 2004.effort to update its water system data so that it can begin further[ s ]BOOTH B, MITCHELL A. Geting Started with ArcCIS[R]. CA,analysis of the systems in its jurisdiction. This process will includeUSA: ESRI, Redlands, 1999.accumulaing water system location information (including sources, [ 6 ]PARKER E HU w, BARNARD K D. Walter System Mapping Projeettreatment plants, distribution systems and sampling sites) with afor the Vancouver Island Health Authority[ C ]. Calgary, Alberta,global positioning system (GPS), and evaluating other available dataCanada: Poster presentation at the 1lth Canadian National Conferencesources in terms of their suitability for the water system project.and 2nd Policy Forum on Drinking Water, 2004.3.2 Challenges with Geocoding Process[ 7 ]MILLS J. Tain't nesarily s0: address geocoding in the real wordThe relatively low match rate of water systems discovered[ EB/OL ]. htp:/e/riconocmps/ibraro/asercr/0p/o//proceed/during the geocoding process can be attributed to a number ofpaperspap623.2003-07-20.factors: the accuracy of the addresses in the file being matched to the( Rreive dale: 20411-20)street reference theme; problems assigning an address to a specific(English edior Profesor HUANG jian- quan )geographic location; and address alocation. More exploration in the中国煤化工MYHCNMHG