Embed Size (px)
Citation preview
Role of Public Health in Preventing Waterborne
Outbreaks
Municipality
Laboratory
Environment UtilityPublic
LicensingOperation
Regulatory Co-operation
Health
Role of EHOs – 2006 Survey published in En. Health Review
• 74% enforcement of drinking water regulation and standards by monitoring water quality (bacteria and chemical) with follow-ups
• 48.6% inspect small, unregulated systems and advising how to correct deficiencies
• 15% assuring that drinking water is safe
What is the role for Health Department ?
POTABLE WATERWHO• Suitable for human consumption and for all
usual domestic purposes, including personal hygiene, washing, showering and domestic food preparation
• Ingestion, contact and aerosol inhalation
• Lifetime exposure
• Not designed for those with high sensitivities and specific immune disorders
Drinking Water Systems
Public Water Systems
Transportation/ Food Private Water Systems
DepotsHaulers
Bottled water, vending
machines, irrigation, ice
Privately owned homes/farms
Non-Transient• Wells, Dugouts,
Cisterns
Transient• Recreational,
Cabins (wells, cisterns)
Non-Approved individual
Non-Approved community
Approved community
Individual municipalities Non-licensed
communityRegional Systems
Distribution only
Non-licensed community
Non-transient• Co-op (<3km,
15 connections), schools, institutions, industries, offices, mobile home parks
Transient• Gas stations,
campgrounds, resorts, restaurants, hotels, motels, B&B, community halls
Drinking Water Systems in Alberta
• Source-to-Tap
• HACCP and Critical Control Points
• Active monitoring and passive surveillance
• Effective and timely declaration of Boil Water Advisory (intervention strategy)
• Promote water safety
• Provide information to public
Multi-barrier approach
CCPs
Prevention
Protection
Role of EHOs – 2006 Survey published in En. Health Review
• 74% enforcement of drinking water regulation and standards by monitoring water quality (bacteria and chemical) with follow-ups
• 48.6% inspect small, unregulated systems and advising how to correct deficiencies
• 15% assuring that drinking water is safe
Microbial Monitoring
Public health focuses on end-product testing - Not the most reliable method of detecting waterborne outbreaks
Problem in depending on water sampling to determine safety of system:
• Small sample size
• Microorganisms not evenly distributed, with clustering and adherence to suspended solids
• 0/100 mL samples is the detection limit
• Most pollution episode are transient
• Sampling only identifies contamination once it has occurred i.e. NOT PREVENTION
• Indicator only and not indicative of Crypto and Giardia
• Fixed time and date for sampling
• E. coli not indicator for non-fecal pathogens especially those capable of multiplying in the distribution system (Legionella and Mycobacteria)
Better solution than microbial monitoring to ensure safety of water is source-to-tap or multi-barrier approach:
- Source water protection and monitoring
- Treatment process optimization and enhancements
- Storage and distribution system integrity
Multi-Barrier Approach
Based on the theory that no single barrier can consistently inactivate or remove all waterborne pathogens, and can be breached by some overwhelming pollution events
Multi-Barrier Approach
Traditional multi-barrier (WHO)
• Protection of source water
• Coagulation, flocculation and sedimentation
• Filtration
• Disinfection
• Protection of the distribution system
Health Canada Source to Tap 2002
Waterborne Outbreaks: Sign, Symptoms and
Prevention
Canada
Report: 1974-2001 (published 2005)
288 WB outbreaks, 99 in public systems, 128 semi- public, 51 private
Main causative agents: Giardia, Campylobacter, Cryptosporidium, Norovirus, Salmonella, HAV
Canada
Causative factor:
Public: water treatment issues, inadequate regulation
Semi-public: septic tanks, water treatment issues, inadequate regulation
Private: septic tanks
Waterborne outbreaks symptoms
(in order of occurrence)
• Watershed events
• Variations in WTP operational parameters
• Occurrence of cases (syndromic surveillance) and consumer complaints
• Etiologic agents found in water
Prevention
Protection
Contamination of Drinking Water
Source water
• Weather or other events over- whelmed log removal ability of the plant
• Understand seasonal variation and peaks in microbial quality as this will influence the requirements for treatment, treatment efficiency and resulting health risk
Contamination of Drinking Water
Source water
• 51% of waterborne disease outbreaks in the US were preceded by precipitation events above 90th
percentile, and 68% by events above the 80th percentile
• One month for surface water and 2- month lag for groundwater contamination events
Contamination of Drinking Water
Source water
• WWTP releases poorly treated effluent during high rainfall or plant failure
• Spreading of biosolids and subsequent runoffs
• Stormwater
• Combined sewer
• Agricultural operations
Contamination of Drinking Water
Source water:
Source water profile and understand environmental signals
Risk evaluation to identify potential contamination sources
Monitoring protocol
Contamination of Drinking Water
Distribution system failure
• Main break, cross-connections, back-siphonage, backflow (20% of pollution events and 50% of outbreaks in France), pressure change due to fire hydrant flushing or usage
0
5
10
15
20
25
30
35
40Groundwater
Distribution System
Treatment Deficiencies
Unknown
Waterborne Disease OutbreaksWaterborne Disease Outbreaks
05
1015202530354045
1993-94 (%)
2000-01 (%)
Last barrier to water supply contamination
1993-4: 27% of WBO in the US traced to distribution systems
2000-01: 16%
Contamination of Drinking Water
Distribution system:
• Main break disinfection protocol
• Cross-connection control
Pathogen Breakthrough
Treatment process failure
• Filtration failure: protozoan
• Disinfection failure: bacteria/virus
Chronic failure: knowledge and training of operator or inadequate equipment
Temporary Failure: human or mechanical error
Pathogen Breakthrough
Treatment process failure
• Understanding the limitation of the plant process and operation, define CCPs, operational and log removal efficiency, particle counter
• Better communication with utility
Pathogen BreakthroughDistribution system failure
• With no barrier and shorter travel time before reaching the public
• Symptoms: Biofilm built-up, stagnant or dead-end lines, high turbidity and low chlorine residual
Pathogen BreakthroughDistribution system failure
• Distribution system monitoring - pressure, turbidity and residual
• Large buildings (institutions) monitoring,
• Consumer complaints
• Security
Waterborne Outbreak: Response and Protection
Detection and Response to Contamination
Detection:
• Monitoring failure– Inadequate microbial monitoring– Inadequate disease surveillance
• Reporting failure
Detection and Response to Contamination
Detection:
• Monitoring failure– E. coli is the primary indicator of
fecal pollution, but must be supported by other measurements such as heterotrophic bacteria, chlorine residual and turbidity
– Inadequate microbial monitoring: hospital and institution water especially for non-fecal pathogens
Detection and Response to Contamination
Detection:
• Monitoring failure– inadequate disease surveillance:
lack of active syndromic surveillance (Milwaukee) and inadequate passive monitoring
Detection and ResponseResponse
• False positive or negative– False Positive: no pathogen in water but
declared BWA due to other indications– False Negative: fail to detect pathogen
Detection and Response
2005 Vancouver:
• “…sample contained a small amount of fecal coliform…our initial assessment indicates that the most likely cause is the contamination of the sample itself during filling of the sample bottle…not prepared to take any chances with the health of our residents…”
Detection and Response
Australia – Sydney Water Crisis July to Sep 1998
• Three BWAs with high Crypto (376/100mL) and Giardia counts (3,952 cysts/100 mL) in finished water
• Cost $37 m in direct cost and $100 million in contingency costs
Detection and Response
Australia – Sydney Water Crisis
• NTU less than 0.02 confirmed by particle count
• Filter working properly meaning raw water must have 350,000 cysts per 100 L (raw sewage)
Detection and Response
Australia – Sydney Water Crisis
• Survey found 64-74% of public complying with BWA, meaning 1 million residents drinking contaminated water
• Enhanced surveillance found no evidence of any increased in diarrheal disease or lab-diagnosed cases
Detection and Response
Australia – Sydney Water Crisis
• Cross-contamination in the lab
• Inquiry: “…when the public is told to boil tap water, it assumes the official directive is scientifically based, and necessary because of clear scientific evidence…yet…seems to be based on…better to be safe than sorry…”
Detection and Response
False Negative:
1994 Las Vegas Cryptosporidium outbreak
• 87 laboratory confirmed cases with 32 dead
• No elevated turbidity, no coliform and no oocysts were found in source or finished water
Detection and Response
Communication failure
• Roles and responsibilities• Food manufacturer, hospitals (engineering, pharmacy, food
services, house keeping), clinics (HIV, dialysis, cancer, pediatric, transplant), LTC, medical and dental associations, senior lodges, jails and correctional services, school boards, franchise restaurant and retail store offices, food safety info lines, water haulers, water depots, swimming pools, family and social services (day care), family day home organizations, shopping malls, major tourist sites, airport authority and caterers, primary food processors (tofu, mushroom, produce, sandwich, soy milk, non-carbonated beverages), commissaries, water vending machines, ice and bottled water manufacturers
Detection and Response
Response - Chemical
• Disinfection by- product (water avoidance advisory)
• Other chemicals
Man-made chemical
Affecting children
Impact future generations
Victim identifiable
Cannot detect
New and exotic
Cancer causing (consequence)
Uncertain in science
Chronic and delayed effect
Individual personally at risk
Exceedance does not necessary mean immediate health concern
MUST understand the numbers
Carcinogen, based on 10-5 lifetime risk ranged from 15.8 to 48.5 µg/L using Risk Specific Dose calculation based on linearized multistage (LMS) method, rounded off to give 16 µg/L
BDCM
Disinfection By-Products
THM - 100 µg/L (with target of 80 µg/L)BDCM - 16 µg/LHAA – 80 µg/LBromate – 10 µg/LChlorate – 1.0 mg/LChlorite – 1.0 mg/L
DBP
Reduce DBP levels in drinking water as low as possible without compromising the disinfection process
THM and BDCM should be used as surrogates to provide some indication of the potential for DBP formation
Prevention
Protection
