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ENH 424- Midterm Exam Guide - Comprehensive Notes for the exam ( 30 pages long!)Premium

30 pages151 viewsWinter 2017

Department
Environmental Health
Course Code
ENH 424
Professor
Ian Young
Study Guide
Midterm

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Ryerson
ENH 424
Midterm EXAM
STUDY GUIDE
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Lecture 1
ENH 424 Water Quality
Drinking Water in Canada
Approx. 45,000 drinking water systems in Canada
o Most are small systems that serve 5000 people or less
Types of drinking water systems vary greatly
o Water can come from surface sources (e.g. lakes, rivers), ground water aquifers
(i.e. wells), cisterns, water trucks, or bottled water
89% of Canadians rely on municipal water systems
o 9% use a private-well
o 1% use a surface water source
Water-borne Illness in Canada
In Canada there is no national surveillance system for systematic collection of water-
borne diseases
o Surveillance is fragmented and outbreaks not always reported beyond local
authorities
Burden of Water-borne Illness
Globally, ~1.8 billion drink faecally contaminated drinking water
Inadequate drinking water is estimated to cause 502,000 diarrhea deaths/year
o In low- and middle-income countries
In the USA, there are ~4-32 million cases of acute gastrointestinal illness (AGI) per year
from public drinking water systems
o For 20112012, 32 drinking waterassociated outbreaks were reported,
accounting for at least 431 cases of illness, 102 hospitalizations, and 14 deaths
Walkerton Outbreak
The high-profile water-borne disease outbreak in Walkerton, Ontario, in May-June 2000
had significant public health and economic impacts
o It brought considerable attention to water quality issues in Ontario and provides
important lessons learned about drinking water system failures and their
consequences
The outbreak caused >2300 cases of GI illness of which
65 were hospitalized
27 developed haemolytic uremic syndrome
7 caused deaths
o Lead to iuiy, pepaed by O’Coo & subseuet efo to safe wate
legislation in Ontario
Town receives water from a number of wells
In May 2000, E. coli O157:H7 and Campylobacter jejuni entered the Walkerton system
through Well 5 on or shortly after May 12, 2000
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o Well 5 was built in 1978
Likely sources was run-off from manure that was spread on a nearby farm
o Preceded by periods of heavy rainfall
The outbreak would have been prevented by the use of continuous chlorine residual and
turbidity monitors at Well 5
Operators lacked proper training and expertise
o Engaged in improper practices, including
Failing to use adequate doses of chlorine,
Failing to monitor chlorine residuals daily,
Making false entries about residuals in daily operating records, and
Misstating the locations at which microbiological samples were take
o They failed to report initial adverse test results to health unit and others, including
a broken chlorinator on one of the wells
o Stan and Frank Koebel charged, pled guilty to common nuisance
MOE inspection failed to detect poor operator practices
Budget reductions led to discontinuation of government laboratory testing services for
municipalities in 1996
Multi-Barrier Approach
Health Canada Drinking Water Guidelines advocate a multi-barrier approach to protect
drinking water quality:
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