Water Quality and Human Health:
Gastro-intestinal Illness in Small Communities in BC
Lindsay Galway¹, Dr. Diana Allen2 & Dr. Tim Takaro1,
¹Faculty of Health Sciences, Simon Fraser University
Introduction
Faculty of Earth Sciences, Simon Fraser University
Preliminary Results
Goals and Objectives
To examine the potential impacts of future climate
change on the risk of waterborne GI illness in small
communities in BC.
Specific Research Objectives
1) Describe the temporal and spatial distribution of GI
illness in the study communities.
2) Examine and quantify the association between
precipitation, extreme precipitation events,
temperature and snow melt and the risk of
waterborne GI illness in the study communities.
3) Establish linkages between the physical
characteristics of the aquifer or surface water system
and the vulnerability for pathogens in water supplies.
Assessing seasonality is a first step in understanding the
relationship between climate and illness. If a seasonal trend
in illness is not detected, it in unlikely that disease risk will
be influenced by variability in climatic variables or climate
change. Seasonality has been established in the pilot
community.
Seasonality of All Cases
Crude Number of Cases
Climate change, in particular changes in precipitation
patterns, an increasing frequency of extreme weather
events and rising temperatures, is expected to impact
both water quality and the distribution disease.
Despite these concerns, research examining the risk of
waterborne GI illness in the context of a changing climate
in small communities is limited, particularly with respect
to sporadic illness, with none specifically exploring this
issue within BC.
Overarching Goal
• A study looking at the risk of enteric illness in relation to
different sources of drinking water of a community in BC’S
lower mainland found that those individuals serviced by
private wells had the highest risk for disease (Uhlmann
2009).
• Although many factors can increase the risk of GI disease,
the role of climatic variables such as precipitation and
temperature have been have been highlighted as
important risk factors.
• Temperature has been associated with an increased risk in
the context of both illness outbreaks and sporadic cases in
a variety of settings (Kovats 2004).
• The role of precipitation as a risk factor for GI is not well
understood however, extreme precipitation events (above
93rd percentile) have been associated with an increased
risk for GI outbreaks by a factor of 2.3 in Canada (Thomas
2006).
Potential Climatic Risk Factors
Heavy
Precipitation
Dry Period +
Heavy
Precipitation
Temperature
Snow
melt
Increased
Risk ?
Sporadic
Waterborne GI
Illness
+
Waterborne
GI Outbreaks
Acknowledgements:
BCCDC, Sunny Mak, Hannah Moffat,
For further information about this project please contact Lindsay Galway at lpg@sfu.ca
30
20
10
0
1997-1998
1998-1999
1999-2000
2000-2001
100
•Study communities were selected to ensure a mix of
water regimes in both rain and snow dominated regions
of the province. This design enables comparisons
between different water regimes as well as other factors
(i.e agriculture) that vary across communities.
Mixed
water
Rain
Snow
LANGLEY KELOWNA
Groundwater
Rain
Snow
DUNCAN TERRACE
&
&
QUALICOM MERITT
Surface
water
Rain
Snow
SIDNEY NELSON
Data and Data sources
•Illness data is a time series of 5 reportable pathogens
(Campylobacteria, Cryptosporidium, Giardia, Salmonella
and Verotoxigenic E. coli.) between 1996 and 2010
extracted from the iPHIS database managed by the BC
Center for Disease Control (BCCDC).
•All environmental data has been extracted from
Environment Canada’s National Climate Data Information
Archive. Variables include: daily maximum, minimum
and mean temperature, daily precipitation and daily
snow depth.
Data Analysis
•Illness cases for each community will mapped using a
GIS to link cases to a water source.
•The association between GI illness and climatic risk
factors will be modeled with a Poison regression adapted
for times series using weekly times series.
•To date, some preliminary results have been generated
examining monthly time series trends in one pilot
community.
400
90
80
70
60
Parasitc
bacterial
50
40
30
20
10
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
2001-2002
2002-2003
2003-2004
2004-2005
Wet Season Cases
Aggregate monthly distribution for
parasitic and bacterial GI cases
1996-2005
• An examination of temporal trends and seasonality in
the illness time series for each community.
Aquifer and Water System Vulnerability
and Water Contamination
50
40
Proposed Methods
Monthly Precipitation (mm/month)
• Waterborne GI illness is a significant public health issue
and water quality is a primary concern among Canadians.
In BC, roughly 400,000 GI illness cases occur each month
with an annual economic burden of approximately $514.2
million (Thomas 2006;Flint 2007).
60
Dry Season Cases
•8 communities from across BC have been selected as
study communities for this project.
DRY: May 15 - Nov 14
WET: Nov 15 - May 14
70
1996-1997
Study Design
Background
90
80
Number of reported GI illness
cases
High-quality drinking water is fundamental to maintaining
human health and well-being. Drinking water quality is
threatened by contamination with waterborne bacterial
and protozoan pathogens that exist in the environment
and enter drinking water supplies via various pathways.
Once pathogens enter a drinking water supply,
waterborne gastro-intestinal (GI) illness outbreaks and
sporadic cases are likely to occur in the absence of
effective water treatment.
The seasonal peak of
bacterial illness occurs in
June/July while the seasonal
peak for parasitic illness
occurs in September. This
difference may suggest a
different pathway of
contamination for parasitic
versus bacterial pathogens
consistent with their different
biology.
Monthly Precipitation & GI Illness Cases
Crude Number of GI Cases (all water sources)
350
20
18
Precipation (mm/month)
16
300
14
250
12
200
10
8
150
6
100
4
50
2
0
Number of Reported GI Cases per Month
2
0
It appears as though there may be an association between
precipitation and illness cases. However, the most
appropriate lag period (time between climatic event and
illness) must be identified to better understand this possible
relationship.
Next Steps
•Further analysis into the characteristics of each community
including: soil types, well characteristics, water system
management and land use patterns.
•If a significant relationship is found between climatic factors
and risk of GI illness, further analysis, such as climate
modeling and projections of future risk will be conducted.
•Findings will be disseminated to a climate change adaptation
audience and to public health and water management
professionals in each study community. This will ultimately
improve water quality protection and prevent illness
protecting human health and well-being in similar climatesensitive water regimes.
References:
Flint, J. A., Dore, K., Majowicz, S. E., Edge, V. L., & Sockett, P. (2004). From stool to statistics - Reporting of acute gastrointestinal illnesses in Canada. Canadian Journal of Public, 95(4), 309-313.
Kovats, R. S., Edwards, S. J., Charron, D., Cowden, J., D'Souza, R. M., Ebi, K. L., et al. (2005). Climate variability and campylobacter infection: an international study. International Journal of Biometeorology, 49(4), 207-214.
Thomas, M. K., Charron, D. F., Waltner-Toews, D., Schuster, C., Maarouf, A. R., & Holt, J. D. (2006). A role of high impact weather events in waterborne disease outbreaks in Canada, 1975-2001. International Journal of
Environmental Health Research, 16(3), 167-180.
Uhlmann S, Galanis E, Takaro T, Mak S, Gustafson L, Embree G, Bellack N, Corbett K, and Isaac-Renton J. (2009). Where's the pump? Associating sporadic enteric disease with drinking water using a Geographic Information
System, in British Columbia, Canada, 1996-2005. Journal of Water & Health.