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Video 5.1: Facts About Water and Health
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Из курса от партнера University of Manchester
Water Supply and Sanitation Policy in Developing Countries Part 1: Understanding Complex Problems
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University of Manchester
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Exploring Health Benefits and Climate Change Issues
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Prof Dale WhittingtonProfessor
Manchester Business School
Dr Duncan ThomasLecturer
Alliance Manchester Business School
This week we're going to talk about two different subjects.
First we're going to look as consequences or outcomes when improved water
services are provided in a community, and these services are in fact used.
Our second topic this week is going to be climate
change and its effects on health and on water utilities.
We'll look at climate change in the later videos for
this week, but first let's start with the subject of outcomes.
To begin, I'd like to make clear that I'm an economist, not an epidemiologist.
Here I'm going to summarize from an economist perspective some important facts
and findings from the literature on water and health in low-income countries.
Fact number one.
Life expectancy increases very rapidly as GDP
per capita increases, and then levels off.
This is one of the most robust findings from
a careful study of status quo conditions and historical experiences.
But note that why this leveling off in life
expectancy occurs in middle income countries is not intuitively obvious.
You could tell an equally plausible story that life expectancy would grow
slowly while a public health infrastructure
platform was being put in place.
And then, when everything was completed, life expectancy would then take off.
In the transition from low-income to
middle-income status, countries undergo many changes simultaneously.
Life expectancy rises, rural households migrate
to cities, water and sanitation conditions improve,
family size declines with the demographic
transition, diet improves and housing conditions improves.
It is very difficult to tease out the cause
and effect relationships because everything is changing at once.
The public health revolution that caused this increase in life expectancy is
in large part due to improved
water and sanitation, diet, vaccines and antibiotics.
But remember we need financing.
You need economic growth to finance piped
water and sewer networks and other health interventions.
Fact number two, childhood mortality rates are
declining and the rate of decline is accelerating.
This is great news.
Not only are things getting better, they're getting better faster.
The global decline from 1990 to 2010 was 2.1% per year for neonatal mortality,
2.3% for post neonatal mortality, and 2.2% for childhood mortality.
Maybe we should just keep doing what we're doing.
But the causes of this decline are not precisely
clear so this might not be a good strategy.
Fact number three, around 20% of the total mortality risk for children under five
years in low-income countries is due to WASH-related diseases.
This works out to about 2 million
children dying annually due to wash related diseases.
In this figure, the vertical axis is the mortality or death rate.
On the horizontal axis, each stack bar shows a different age cohort.
The colors on a bar show the causes of death.
One observation is that for all causes children are
dying at about the same rates as 55 to 65-year-olds.
The fact that 2 million children are dying
from WASH-related diseases is a tragedy and morally unacceptable.
But the fact that 8 million children are
dying annually from other causes is also a tragedy.
It's important to appreciate that parents see lots
of risk facing their children, not just WASH-related diseases.
And parents do not just look at the risk
to their children, they must also consider opportunities for them.
And then parents must strike a difficult balance in
allocating their resources to maximize opportunities and minimize risks.
This is no easy task.
Fact number four.
Almost no one in high-income countries dies of WASH-related diseases.
This is true for all age cohorts.
Industrialized countries have, for all intents and purposes,
solved the problem of high infant mortality in general.
And in so doing they have solved the
specific problem of children dying from WASH-related diseases.
It is useful to look back in history and try to learn how
countries that are rich today managed to reduce infant mortality in the past.
One of the key factors was improved water and tan, sanitation services.
But it is important to look
carefully where these improved services were delivered.
What kinds of housing units received improved water and sanitation services?
This photograph shows the streets of lower Manhattan, in the late 19th Century.
In this slide, the photograph on the left shows a
densely crowded tenement building in lower Manhattan, in New York.
This photograph on the right shows young children playing
in open sewers with a dead horse in the background.
Typhoid and cholera rates in lower Manhattan in the
19th Century were much worse than in Calcutta today.
In many situations, improved water and sanitation services were
not delivered to slums like those shown in this photograph.
Instead, slums were torn down and new water and
sanitation services were delivered to new, improved housing units.
Precisely the same thing is happening in many developing countries today.
Housing and water and sanitation infrastructure
are being improved at the same time.
One lesson here is the importance of
mortgage finance to improve housing affordability and conditions.
Improved water and sanitation services will probably have a larger effect
on health outcomes when housing is improved at the same time.
Fact number six.
WASH interventions reduce diarrhea by around 30%.
This figure is from a meta-analysis of studies of the
causal relationship between water and
sanitation interventions and health outcomes.
In this case the held outcome is the reduction of diarrhea
risk, measured as a percentage reduction in the incidents from baseline conditions.
The authors only included the studies that they judged in be high quality.
There are five types of water
and sanitation interventions included in the table.
Hygiene, water supply, sanitation, water quality improvements,
and combinations of intervention that is, multiple interventions at the same time.
This is an important figure.
You will probably want to come back later and study it in detail.
But I want to point out a few things for you now.
First, the water supply intervention alone has very modest effect on diarrhea risk.
Some studies do not even find a statistically significant effect.
Second, both hygiene and water quality improvement interventions
reduce diarrhea risk by about 30 to 40%.
Third, multiple interventions do not reduce
diarrhea risk more than single interventions.
Multiple interventions do not seem to increase health benefits.
This is a puzzle.
What's going on here?
This diagram is called the F diagram and it's
a famous figure in the water and health literature.
On the left, you have faeces.
And on the middle, you have four ways that faeces can reach future victims.
Fluids, fingers, flies and floors can all reach future
victims through the food chain as well as directly.
So I've added food here in the F diagram to show that there are the
multiple ways that the fluids, fingers, flies
and food pathways can reach the future victim.
Now let's look at future, interv, let's look at
interventions and see how they can block these pathways.
Water supply only blocks these two pathways at the top from fluids.
So this explains, or may explain why the effect of water supply interventions.
Doesn't reduce diarrhea as much as we might have thought.
Sanitation, on the other hand, blocks the, controls faeces and blocks
the pathways for flies, floors, and fluids, but it doesn't block fingers.
So faeces can still get on fingers, and fingers
can reach food and still affect the future victim.
So, if we add hygiene.
These two bars show hand washing after defecation on the
left and then after, before food eating on the right.
We can potentially block all pathways where faeces can reach the future victims.
But this doesn't explain why multiple interventions don't work.
Maybe there are other pathways.
Maybe education matters here.
Well it could be that some of
the interventions are not being implemented effectively.
Fact number seven.
In rapidly growing economies, access to
piped water is correlated with reduced mortality.
We've already seen in week one, when we were discussing water and
sanitation coverage, that access to pipe
water is correlated with reduced mortality.
But in low-income countries and among the poor, the evidence is less clear.
This finding may be related to the result we had before that
multiple interventions do not seem to
reduce diarrhea more than single interventions.
Fact number eight.
Piped water supply can even cause health conditions to deteriorate.
In this paper about the effects of improved water supply, in Sibou,
Philippines, Daniel Bennett argues that piped
water supply actually made health conditions worse.
I didn't understand how this could happen until I went to a very crowded
slum in Delhi as part of a cholera vaccination project a few years ago.
If you bring piped water supplies into very dense slums with no drainage or
sanitation, you've created a very efficient pathway to spread pathogens.
As Bennet says in the paper, water supply
improvements may unintentionally cause community sanitation to worsen.
This is what I saw in Delhi, and this is consistent with the finding from the
meta-analysis, that water supply interventions alone have a
smaller, even statistically insignificant effect on health outcomes.
Fact number nine.
It's not clear that education helps.
Many health professionals have held out hope that education in general, and
health education in particular, will change
behaviors and improve water and sanitation outcomes.
But in a series of carefully done
empirical studies in Kenya, Professor Michael Kramer
at Harvard, has raised serious doubts about
the effects of education on health outcomes.
He found that, first, school health
education did not affect health-seeking behaviors.
And second, there was lower uptake of
health interventions among those with more knowledge.
It's not clear that these conclusions are
generalizable to other locations, but for me
as an economist, Michael Kremer's papers have
made for very sobering reading and much reflection.
Every sector has a story of about how
increased investment in their sector will lead to
better lives and more productive labor, more savings,
and households will climb out of a poverty trap.
Water sector professionals often tell a story about how investments in improved
water will result in better health and save time spent collecting water.
And this will start a virtuous cycle that
will enable households to escape from a poverty trap.
But it is obvious that all these sector stories cannot be true.
If they were, anything you did would lead you out of a poverty trap.
In this case, it wouldn't be a trap.
It would be so easy to get out.
But the cruel reality of health improvements in a
Malthusian economy is that they lower average household incomes.
In a Malthusian economy, population increases
outpaced resources and drive down wage rates.
Unfortunately, many people in the bottom billion live in a Malthusian economy.
In a Malthusian economy, water and sanitation interventions that
improve health, however, may be good for other reasons.
But they won't get you out of a poverty trap.
To wrap up, water and sanitation interventions
are occurring in a rapidly changing world.
There is much that is still hard to pin down about
the relationship between improved water and
sanitation services and improved health outcomes.
But from my perspective as an economist,
I don't think there's much practical value in
doing more water and health studies for
the purpose of justifying water and sanitation investments.
The health outcomes of water and sanitation interventions are
always going to be uncertain in a dynamic economy.
I will talk more about the sources of this uncertainty in the next video.
A good rule of thumb is that a well executed water and
sanitation intervention will reduce diarrhea cases
in a community by about a third.
But don't expect a much more dramatic decrease
than this, at least, until housing conditions have improved.
The effect of health outcomes from water and sanitation investments
on local economies will be very location and time specific.
It's very difficult to generalize about the effects
of water and sanitation investments on economic growth.
But this is no reason to be timid or indecisive about such investments
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