- Количество слайдов: 23
Water, sanitation, hygiene & environmental health Pete Kolsky Energy and Water Department
Outline n n n 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 n Faecal-oral (focus of this presentation) n Diarrhoeal disease n 2 million deaths/year from diarrhoea, mostly under 5 n n n n 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 n Arsenic n n 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 n n Dental damage, crippling bone damage “affects millions” (WHO) but often of mild form
Historical evolution: water quality and health n n n John Snow 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 outbreaks 1. True outbreaks…sudden spikes n Very visible and dramatic!! n Politically hot! 2. Common source…the water supply 1. If you’re a water engineer…you don’t want one on your watch! 2. Cholera is the water engineer’s best friend…Money for chlorine suddenly becomes available… 3. Until 1970 s, water quality dominated environmental health perception of diarrhoea
Classifications of disease n n Classification usually by organism (viral, bacterial, etc) or organ (diseases of head, heart, liver etc. ) Classification by transmission route n n n Bradley’s great innovation in 1970 s If you know how it’s spread, you know how to stop it… …so engineers loved it!
The F-Diagramme Water supply Sanitation Fluids Hygiene Fingers Faeces Food Flies Fields/ Floors Future Victim
The great debates of the 80 s n n Water-borne or water-washed? n 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 n One-to-one (clustreing) n Confounding variables (inc. age) n Recall n Diarrhoeal definition n Usage n Seasonality These issues are real, and are still grave threats to ‘quick and dirty’ project level impact assessments!! n n
Results from Esrey, 1985 Type of Intervention All interventions No of Results 53 Median Reduction 22 Range Water quality 9 16 0 -90 Water availability 17 25 0 -100 Water quality and availability Excreta disposal 8 37 0 -82 10 22 0 -48 0 -100 (Esrey, S. A. et al. , WHO Bull, 63(4): 757 -772, 1985)
Esrey (1985) by disease Disease or infection Cholera No of results 11 Median reduction 41 Shigella 27 48 0 -81 Entamoeba histolytica Giardia lamblia 17 2 0 -80 10 0 0 -20 Range 0 -91
Esrey’s update in 1991 Intervention Water & San Rigorous All Studies No Med % reduct 7 20 2 30 Sanitation Water Quality and Quantity 11 22 22 16 5 2 36 17 Water Quality 7 17 4 15 Water Quantity 7 27 5 20 Hygiene 6 33 Esrey et al. , WHO Bull, 69(5): 609 -621 (1991)
2004 Fewtrell, Colford update n Why do more? n n n 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 reduce diarrhoea in less developed countries: a systematic review and 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
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. Taken from S. Cairncross RWSSTG BBL “ The Health Impact of Sanitation”, Aug 2004.
Major new conclusions from Fewtrell, Colford, Kaufmann n Water quality at HH is shown as significant… n n n 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… n We don’t live in an “average” world… n n n 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… n If disease incidence not linearly proportional to transmission, then “impact” attribution easily skewed
The F-diagramme revisited Water supply Sanitation Fluids Hygiene Fingers Faeces Food Flies Fields/ Floors Future Victim
How people see their city River & Environs City Home Peri- Ward domestic (street, school, workplace)
An environmental view Home Peridomestic Ward (street, school, workplace) City Central Treatment Works Collectors Street Sewers House Connections
A public health view Sewer Mains River & Environs Street Sewer City Interceptor/ Collector Treatment Plant/Outfall Home Peri- Ward domestic House Connection
Take home messages… n n n Diarrhoea is a huge problem in child health Water, sanitation and hygiene can reduce diarrhoea between 25 -50%… Very broad consensus that: n n n 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.
Thank you for your attention!