Wednesday 30 June 2010

Rose George

Rose George, author of the splendid The Big Necessity: Adventures in the World of Human Waste, has written a short article “Beating boring, banal diarrhoea” in last Saturday’s issue of The Guardian (a UK daily newspaper). As to be expected from such a good writer, it’s a brilliant piece – read it!

Water, sanitation, women and children

Here’s an interesting World Bank Policy Research Working Paper: Access to Water, Women’s Work and Child Outcomes, by Gayatri Koolwal and Dominique van de Walle (both of the World Bank), published in May this year. This is the Abstract:

Poor rural women in the developing world spend considerable time collecting water. How then do they respond to improved access to water infrastructure? Does it increase their participation in income-earning market-based activities? Does it improve the health and education outcomes of their children? To help address these questions, a new approach for dealing with the endogeneity of infrastructure placement in cross-sectional surveys is proposed and implemented using data for nine developing countries. The paper does not find that access to water comes with greater off-farm work for women, although in countries where substantial gender gaps in schooling exist, both boys’ and girls’ enrolments improve with better access to water. There are also some signs of impacts on child health as measured by anthropometric z-scores.

Anthropometric z-scores? See here.

Could the same approach be taken for rural sanitation? I don’t see why not.

There’s another very pertinent World Bank Policy Research Working Paper: Water, Sanitation and Children’s Health Evidence from 172 DHS Surveys, by Isabel Günther of ETH Zürich and Günther Fink of the Harvard School of Public Health, published in April. Here’s the Abstract:

This paper combines 172 Demography and Health Survey data sets from 70 countries to estimate the effect of water and sanitation on child mortality and morbidity. The results show a robust association between access to water and sanitation technologies and both child morbidity and child mortality. The point estimates imply, depending on the technology level and the sub-region chosen, that water and sanitation infrastructure lowers the odds of children to suffering from diarrhea by 7–17 percent, and reduces the mortality risk for children under the age of five by about 5-20 percent. The effects seem largest for modern sanitation technologies and least significant for basic water supply. The authors also find evidence for the Mills-Reincke Multiplier for both water and sanitation access as well as positive health externalities for sanitation investments. The overall magnitude of the estimated effects appears smaller than coefficients reported in meta-studies based on randomized field trials, suggesting limits to the scalability and sustainability of the health benefits associated with water and sanitation interventions.

Mills-Reincke Multiplier? The following explanation comes from the 1910 paper On the Mills-Reincke phenomenon and Hazen's theorem concerning the decrease in mortality from diseases other than typhoid fever following the purification of public water supplies by W. T. Sedgwick and J. S. MacNutt, published in the Journal of Infectious Diseases (volume 7, issue 4, pages 489–564):

It is nowadays commonly understood that the purification of a polluted water-supply produces a marked decrease in the mortality from typhoid fever among persons using the water for drinking and other domestic purposes, but it is not as yet generally recognized that such purification produces also a marked decrease in deaths from other diseases. In 1893−94 it was observed, independently, by Messrs. Hiram F. Mills, C.E., of Lawrence, Massachusetts, and Dr. J. J. Reincke, of Hamburg, Germany, that the purification of the polluted public water-supplies of Lawrence and of Hamburg, respectively, was producing a notable decline in the general death-rate of each of these cities. The attention of Mr. Allen Hazen was about the same time turned to the subject, and some years later, in a paper presented to the International Engineering Congress held at the St. Louis Exposition in 1904, he drew from an examination of the death-rates of certain cities which had radically improved polluted water-supplies the following conclusion:

Where one death from typhoid fever has been avoided by the use of better water, a certain number of deaths, probably two or three, from other causes have been avoided.

This novel statement has not hitherto received the attention which it deserves …

Tuesday 29 June 2010

One of the 50 best blogs for civil engineers!

This blog is one of the "50 Best Blogs for Civil Engineers" as posted on the Top Online Engineering Degree website. Very gratifying to know this − thank you!

Environmental disease transmission

Here’s a very interesting and splendidly mathematical paper: Dynamics and control of infections transmitted from person to person through the environment by Sheng Li, Joseph N. S. Eisenberg, Ian H. Spicknall and James S. Koopman published in May last year in the American Journal of Epidemiology. Here’s the Abstract:

The environment provides points for control of pathogens spread by food, water, hands, air, or fomites. These environmental transmission pathways require contact network formulations more realistically detailed than those based on social encounters or physical proximity. As a step toward improved assessment of environmental interventions, description of contact networks, and better use of environmental specimens to analyze transmission, an environmental infection transmission system model that describes the dynamics of human interaction with pathogens in the environment is presented. Its environmental parameters include the pathogen elimination rate, µ, and the rate humans pick up pathogens, ρ, and deposit them, α. The ratio, ρN/µ (N equals population size), indicates whether transmission is density dependent (low ratio), frequency dependent (high ratio), or in between. Transmission through frequently touched fomites, such as doorknobs, generates frequency-dependent patterns, while transmission through thoroughly mixed air or infrequently touched fomites generates density-dependent patterns. The environmental contamination ratio, α/γ, reflects total agent deposition per infection and outbreak probability, where γ is defined as the recovery rate. These insights provide theoretical contexts to examine the role of the environment in pathogen transmission and a framework to interpret environmental data to inform environmental interventions.

Fomites? See here.

WASH and diarrhoea

I’ve just come across a really good paper: Effectiveness and sustainability of water, sanitation, and hygiene interventions in combating diarrhoea, by Hugh Waddington and Birte Snilstveit, both of the International Initiative for Impact Evaluation (3ie) in New Delhi, which was published in last September’s issue of the Journal of Development Effectiveness (volume 1, issue 3, pages 295–335). Here’s the Abstract:

This paper presents a synthetic review of impact evaluations examining the effectiveness of water, sanitation, and hygiene interventions in reducing diarrhoea among children. The evaluations were conducted in 35 low- and middle-income countries during the past three decades. The paper challenges the existing consensus that water treatment at point-of-use and hygiene interventions are necessarily the most effective and sustainable interventions for promoting the reduction of diarrhoea. The analysis suggests that sanitation ‘hardware’ interventions are highly effective in reducing diarrhoea morbidity. Moreover, while there is a wealth of trials documenting the effectiveness of water treatment interventions, studies conducted over longer periods tend to show smaller effectiveness and evidence suggests compliance rates, and therefore impact, may fall markedly over time [emphasis added].


Catholic Relief Services (see their Water and Sanitation page) have just published Rapid Assessment of CRS Experience with Arborloos in East Africa by Paul Hébert. It’s a really interesting account of the large-scale implementation of this terrific rural sanitation technology. Here’s an excerpt from the Executive Summary:

From 2005 to 2009 in Ethiopia, 53,840 households in 7 regions installed Arborloos with the help of CRS and partners. … In Ethiopia, the large number of Arborloos constructed by households from 2005 to 2009 was nearly ten times the number of conventional latrines built between 1995 and 2004, which were found to be more costly and difficult for households to construct. CRS considers this expansion to be a major breakthrough with the potential for significant scale up.

The cost per household? Very little: USD 16 in Ethiopia and USD 19−21 in Kenya, Tanzania and Uganda.

Hygiene and Sanitation Software

The Water Supply and Sanitation Collaborative Council has recently published Hygiene and Sanitation Software: An Overview of Approaches by Andy Peal, Barbara Evans (who works with me in Leeds) and Carolien van der Voorden. A truly excellent publication! Here’s what it says it’s all about:

This document describes the various hygiene and sanitation ‘software’ approaches that have been deployed over the last 40 years by NGOs, development agencies, national and local governments in all types of settings – urban, informal-urban and rural.

There are many different software approaches and there is often confusion over, for example, what a particular approach is designed to achieve, what it comprises, when and where it should be used, how it should be implemented or how much it costs. There is currently no reference material that explains the different approaches available or helps practitioners
decide which one would be best to use for a particular situation. Moreover, the many ‘acronyms’ and ‘brand names’ in use frequently mean different things to different people.

Therefore, the purposes of this document are to clarify some of the confusion in the sector about the terminology and language used and provide a ‘ready reference’ or introduction to some of the more commonly used approaches. It is intended to be used as a resource tool both by a newcomer to the subject and by the more experienced practitioner who wishes to gain knowledge of other approaches with which he or she is not familiar.

Last year WSSCC published Public Funding for Sanitation: The Many Faces of Sanitation Subsidies by the same authors. Another crackingly good report!