Water, sanitation, hygiene & health:
Implications for MUS approaches
Jenna Davis
Stanford University
26 April 2006
Davis 2006
Outline
 A historical
note
 Health impacts of water-related illness
 Classification of water- and sanitationrelated disease
 The quantity/quality debate
 Implications for MUS approaches
Davis 2006
A historical note
Modern W&S networks were first developed
out of concerns for public health
 Debate
regarding cause of illness (pythogenic
versus germ theory of disease)
 Beliefs
(and misunderstandings) about
exposure routes shaped investment
priorities, development of W&S
infrastructure
Davis 2006
W&S services and health
Direct effects
Half the developing world suffering from a
water- or sanitation-related disease (UNICEF)
 3-7 million deaths each year (WHO)

Indirect effects
Injuries
 Foregone child care

Davis 2006
Types of water- and sanitation-related disease
(WHO)
 Water-borne: Contaminated water or food
(e.g., cholera)
 Water-based: Parasites within water habitat
(e.g., Guinea worm, schistosomiasis)
 Water-washed: Inadequate hygiene (e.g.,
trachoma)
 Water-related: Insects near water habitat
(e.g., malaria, dengue)
Davis 2006
Annual
morbidity
384,000
Annual
mortality
11,000
Cholera
Waterborne
Typhoid
Waterborne
5,000,000
125,000
Dracunculiasis
(Guinea worm)
Schistosomiasis
(bilharzia)
Waterbased
11,500
<1,000
Waterbased
200,000,000
300,000
Trachoma
Waterwashed
500,000,000
-
Malaria
Waterrelated
400,000,000
1,500,000
Dengue
Waterrelated
50,000,000
200,000
WHO data, 1997-2004
Davis 2006
What about diarrhea?
 Most prevalent W&S service-related disease
 4 billion cases annually, 1.8 million deaths
(2004); ~90% of victims are children <5
 4% of all deaths and 6% of health loss to
disability
 Both waterborne and water-washed types
exist—debate as to which is more prevalent
Davis 2006
Is the etiology of diarrhea so important?
Global deaths
per year
Water-borne diarrhea
Water-washed diarrhea
Other water-borne
Other water-washed
Water-based
Water-borne
Water-washed
Water-based
Water-related
Water-related
Davis 2006
 Controlling waterborne diseases
requires access to a water source
of high quality
 Controlling water-washed diseases
depends on easy access to large
quantities of water and good
hygiene practices
 Controlling water-based diseases
depends on elimination of contact
with the infected water source
 Controlling water-related diseases
depends on decreased exposure to the
vector
Davis 2006
Beliefs (and misunderstandings?)
about the relative contribution of
different exposure routes are shaping
investment priorities, development
of W&S infrastructure
Davis 2006
Significance of this debate for MUS?
 Where MUS involves irrigation and other uses
with freshwater (“productive plus”), growing
consensus on quantity over quality in the W&S
sector is good news.
 Net health impacts likely to be positive, even
absent concomitant water treatment investment
 Implies few substantial institutional / regulatory
changes (pubic health perspective)
 Exceptions might include pesticide contamination
Davis 2006
Significance of this debate for MUS?
 Around the world, the trend is toward irrigation
with increasingly lower quality water.
 When are benefits of increased quantity of water for
domestic uses exhausted by negative effects of lower
quality?
 Health concerns for direct ingestion as well as
indirect exposure to pathogens through food
 Existing WW standards address latter issues but not
former
 Suggests the need for a more complex institutional/
regulatory framework to protect public health
Davis 2006
Significance of this debate for MUS?
 Ensuring adequate supplies of potable drinking
water within a MUS framework
 Investment in potable water storage
infrastructure (e.g., rainwater harvesting)
 Household-level water treatment (“point of
use”)
Davis 2006
Significance of this debate for MUS?
 Point-of-use water treatment for microbial
contamination
 Physical processes (heat): boiling, thermal
disinfection, UV disinfection
 Physical processes (particle removal): filtration
(sand, ceramic, sari cloth, etc.), coagulation,
flocculation (alum, iron hydroxides), settling
 Chemical disinfection: chlorine, iodine
Challenges for sustainability (e.g., continued
protocol compliance, supply chains, O&M) and
for equity (e.g., affordability of access)
Davis 2006
Significance of this debate for MUS?
 Water quality: “reality” vs. perception
 Eastern Islands, Indonesia: Functional piped
systems unused because of local responses to
chlorine
 Manila, Philippines: ~40% of HHs using
‘protected sources’ regularly treating water
(boiling & filtering)
 California: ~70% of HHs rely principally on
bottled or filtered water for drinking in the
home
Davis 2006
Conclusions
 In both irrigation and W&S service
literatures, evidence from users that
bifurcated planning produces outcomes
that fail to meet users’ needs
 MUS approaches may create, reduce, or
have no effect on W&S-related health
problems
 Current treatment of W&S-related health
concerns in MUS literature appears limited