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Outline Some facts about water, san and
health Historical evolution Classification by transmission The Literature of impact studies The nature of the problem Conclusions for practitioners
Some water, sanitation and health numbers
Faecal-oral (focus of this presentation) Diarrhoeal disease
2 million deaths/year from diarrhoea, mostly under 5 Jumbo jet crash every hour and a half…
One billion cases/year 4.3% of Burden of Disease DALYs 88% (?) attributable to inadequate WSH
1/3 of developing world pop’n carry intestinal worms 200 million infected by schistosomiasis (bilharzia)
6-9 million blind from trachoma (1/4 reduced by adequate water supply)
Natural chemical hazards Arsenic
Skin lesions, various cancers “20 to 60” million exposed in Bangladesh Major problem other parts of S. Asia, also
Argentina, Chile, China, Hungary, Mexico, Peru
Fluorosis Dental damage, crippling bone damage “affects millions” (WHO) but often of mild
form
Historical evolution: water quality and health
John Snow Cholera Broad Street Pump 1854
Water Companies' Studies William Budd Typhoid in 1850's-60's Koch Cholera vs.
Pettenkoffer Hamburg/Altona 1892 1937 Croydon Typhoid And many more…
Characteristics of these (and other) waterborne
outbreaks1. True outbreaks…sudden spikes
Very visible and dramatic!! Politically hot!
2. Common source…the water supply If you’re a water engineer…you don’t want one on
your watch! Cholera is the water engineer’s best friend…
Money for chlorine suddenly becomes available…
3. Until 1970s, water quality dominated environmental health perception of diarrhoea
Classifications of disease
Classification usually by organism (viral, bacterial, etc) or organ (diseases of head, heart, liver etc.)
Classification by transmission route Bradley’s great innovation in 1970s If you know how it’s spread, you know
how to stop it… …so engineers loved it!
The F-Diagramme
Faeces
Future Victim
Fluids
Fingers
Flies
Fields/Floors
Sanitation
Food
Hygiene
Water supply
The great debates of the 80s Water-borne or water-washed?
Is water quality or water quantity more important? Review of epi in ‘83 revealed fundamental challenges
Blum, D. and R. Feachem, Int J Epidemiol 1983, 12, pp. 357-365 Lack of control One-to-one (clustreing) Confounding variables (inc. age) Recall Diarrhoeal definition Usage Seasonality
These issues are real, and are still grave threats to ‘quick and dirty’ project
level impact assessments!!
Results from Esrey, 1985
Type of Intervention
No ofResults
MedianReduction
All interventions 53 22
Water quality 9 16
Water availability 17 25
Water qualityand availability
8 37
Excreta disposal 10 22
(Esrey, S.A. et al., WHO Bull, 63(4): 757-772, 1985)
Range
0-100
0-90
0-100
0-82
0-48
Esrey (1985) by disease
Disease or infection
No of results
Median reduction
Cholera 11 41
Shigella 27 48
Entamoeba histolytica
17 2
Giardia lamblia
10 0
Range
0-91
0-81
0-80
0-20
Esrey’s update in 1991
Esrey et al., WHO Bull, 69(5): 609-621 (1991)InterventionNo Med
%reduct
No Med % reduct
Water & San 7 20 2 30Sanitation 11 22 5 36Water Quality and Quantity 22 16 2 17Water Quality 7 17 4 15Water Quantity 7 27 5 20Hygiene 6 33 6 33
All StudiesRigorous Studies
2004 Fewtrell, Colford update
Why do more? More studies Statistically rigorous meta-analysis HH water treatment new player
“Water, sanitation and Hygiene: Interventions and diarrhoea A systematic review and meta-analysis”, Lorna Fewtrell and John M. Colford, Jr. HNP Discussion Paper, World Bank 2004.
Water, sanitation, and hygiene interventions to reducediarrhoea in less developed countries: a systematic reviewand meta-analysis, L. Fewtrell, R. Kaufmann, et al. Lancet Infectious
Diseases, Vol 5, pp 42-52. Jan 2005.
Some of the main results
•Above are highlights…
• Strong, detailed report and bibliography, and documentation of approach
No studies
% reduction lower upper
Multiple interventions 5 33 24 41Hygiene (good studies) 8 45 25 60Sanitation 2 32 13 47Water House Conn (good studies) 1 38 35 41HH treatment (good studies) 8 39 19 54
Previous reviews:
a – d Esrey SA et al. (1991) Bull WHO 69 (5): 609-621
e Curtis V, Cairncross S (2003) Lancet Inf Dis 3: 275-281.
0
10
20
30
40
50
60
70
(a) Sanitation (b) Wateravailability
(c) Waterquality
(d) Hygienepromotion
(e) Handwashing
Red
uct
ion
in
dia
rrh
ea m
orb
idit
y (%
)
Previous reviews Fewtrell et al. (2004)
Taken from S. Cairncross RWSSTG BBL “ The Health Impact of Sanitation”, Aug 2004.
Major new conclusions from Fewtrell, Colford, Kaufmann
Water quality at HH is shown as significant… further reviews forthcoming…some skeptics
remain Hygiene is reconfirmed as an effective
intervention Combining interventions does not
appear to have synergistic effect, contrary to popular public health belief
A step back from all of this…
We don’t live in an “average” world… Mountains of Peru are different from slums
of South Asia e.g. soil and food contamination risks higher
in China, Vietnam than in Africa… Briscoe (Briscoe, J., Am J Epidemiol
1984;120:449-55) sheds even more light in a non-linear world… If disease incidence not linearly proportional to
transmission, then “impact” attribution easily skewed
The F-diagramme revisited
Faeces
Future Victim
Fluids
Fingers
Flies
Fields/Floors
Sanitation
Food
Hygiene
Water supply
(street,school, workplace)
Peri-domestic
Street Sewers
Home
House Connections
An environmental view
Central Treatment Works
City
Collectors
Ward
Ward
Sewer Mains
House Connection
Home
Peri-domestic
Street Sewer
City
Interceptor/ Collector
River & Environs
Treatment Plant/Outfall
A public health view
Take home messages… Diarrhoea is a huge problem in child health Water, sanitation and hygiene can reduce diarrhoea
between 25-50%… Very broad consensus that:
Focus on the household… Hygiene matters! Water quality matters, but it’s not “just” water quality…
faecal contamination gets around many ways Sanitation, WS infrastructure can make hygiene possible!
Health studies are tough…live with indicators rather than “health outcome”
HH water treatment continues to be a growing focus of attention…perhaps even more relevant for chem. contam.