Transcriber: Bob Prottas Reviewer: Denise RQ
About 25 years ago,
I graduated with a PhD in semiconductor physics,
which is an area of physics completely unrelated to human health or medicine.
And that was alright because I was to rock the physics world,
particularly the solid state world,
but my girlfriend who is my current wife
(Laughter)
she refused to marry me unless I had a permanent job.
So I very quickly found myself teaching physics
to medical students in the College of Surgeons.
And I was there no longer than maybe 2 or 3 weeks
when, one morning, the door to my office burst open
and a very distinguished-looking elderly gentleman walked in,
rapped my desk with his walking stick and said:
"I believe you're the new physicist chappy.
I'd like you to help me save lives with sunlight."
And who can resist an opening line like that?
He had me at 'Hello.'
(Laughter)
This was Dr. Joe Barnes.
He was a retired lecturer in tropical medicine.
He was in his mid 70s then - he's still alive, he's nearly 100 -
and he was the person who opened my eyes to the problems
that nearly 800 million people have around the world every day
getting access to safe drinking water.
So what I'd like you to do for a moment
is think about the last drink of water that you had.
Maybe you bought a bottle of water from a vending machine,
maybe you filled a cup at a sink from a tap.
I can guarantee you, whatever trouble you went to is peanuts
compared to what hundreds of millions of people do every day around the world.
People like this girl.
I photographed this in the Kuru, in Kenya, in one of the slum areas.
Now, there is treated water available through the municipal supply,
but unscrupulous landlords lock the standpipes,
and they force the tenants to pay for access to the water.
So the locals being the ingenious people that they are,
they'll find out where the pipes are,
they'll chip away the concrete, exposing the pipe, then they'll cut it,
and they'll collect the treated water.
But if you look at that photograph,
the girl is collecting safe drinking water in the jug.
But the bottom of the jug is dipping into raw sewage in an open sewer.
Would you like to drink that water?
If you're outside of the cities, in the rural areas,
who knows, the nearest water source could be up to 6 or 7 kilometers away.
I'm a physicist, measurement is my life.
Water is quite dense: one liter weighs one kilogram,
so a 20-liter jerry can will weigh 20 kilograms.
If you're lucky, you'll have a donkey to carry it for you.
But more than likely you won't.
And you'll end up walking along deserted country roads.
The burden of water collection usually falls
on either the females or the children in the household.
When you get to the waterhole there's all kinds of other problems.
You may have to wait 2 hours in line waiting for access to the water source.
During that period of time, you could be subjected to social
physical or sexual abuse.
And all of this to get water that most of us wouldn't wash our car with.
This is the world that Dr. Joe Barnes opened me up to.
Now you could treat the water.
When you get it back to the homestead you can boil it.
It's a fantastic way of treating water.
But you'll have to collect the fuel. So that takes time and energy.
If you're in an urban situation, you might have to buy the fuel.
You can filter. This is a bio-sand filter. There are other filters, ceramic filters.
They're all very effective. They're all quite expensive.
You could chlorinate the water. But you'll have to buy tablets.
So the tragedy is the people most in need of access to safe water
are the ones who can't afford to buy it.
And this is where Joe Barnes came in.
Because he'd worked all over the developing world.
He'd worked in refugee camps. He'd worked in leper colonies.
And he'd noticed that no matter how poor a situation
there was always a well-known fizzy drink on sale
and the empty bottles littered the area.
And he thought, well, maybe we can use these bottles.
They don't cost anything.
Put the water in it and use the abundant sunlight to disinfect the water.
So he was the man who introduced me to solar disinfection of water.
It was an idea that he had.
He wasn't necessarily the first person to have the idea.
There's records of Indian communities putting water into trays,
placing those outside to be blessed by the sun.
And they did this 200 years ago.
So he may not have invented it but he was the person who introduced me to it.
So solar disinfection it's very simple.
You get yourself a plastic bottle. It doesn't have to be plastic.
It could be a glass bottle. It doesn't have to be a bottle.
It can be a plastic bag. As long as it is transparent.
You fill it with the available water that you've collected.
And then you put it out into direct sunlight and you wait.
We recommend that you wait for a minimum of 6 hours.
Whenever we introduce it into a community we find very quickly that people
will start putting the water out in the morning
and then leaving it the full day and collecting it the following morning.
So you're drinking today what you disinfected yesterday
and you have 2 sets of bottles on the go.
So that's solar disinfection. Incredibly simple. Costs nothing.
It's by far the cheapest method of water treatment.
This was Joseph's suggestion to me
and he wanted me to set up some experiments to see that it worked.
I was thinking:
"Oh Joe that sounds very much like a solar incubator that you've described to me."
I'd really didn't have much faith in what he was saying to me.
But I'm an experimental physicist who'll do the experiment.
We'll find out. We got some bottles.
We filled them with water and then we inoculated it
with populations of about a billion e-coli. That's a thousand million.
That's more or less the equivalent of a small pooh in a big bottle.
(Chuckling)
And we put them on a windowsill at the front of the College of Surgeons
on St. Stephen's green on a sunny June day.
And I stood back fully expecting this to be an absolute disaster.
But incredibly we found no detectable bacteria in under 4 hours.
And if we put foil on the back of the bottle
and the photons that go through were reflected off the back
and had a second bite of the bacterial cherry,
we got complete inactivation in under an hour.
So bacteria, we found, were very amenable to solar disinfection.
Bacterial pathogens aren't the only type of waterborne pathogen.
You may recall 5 or 6 years ago
Galway, the third largest city in the Republic of Ireland,
had its water system contaminated with Cryptosporidium.
A lovely protozoan pathogen.
The infective form are these oocysts and very resistant to chlorine.
It turns out, not so resistant to solar disinfection.
You can see the damage that the sunlight has had
on outer surface of the bacteria of the protozoa.
And it turns out, in the 25 years that we've been looking at this,
we've never found a waterborne pathogen that was resistant to solar disinfection.
The reason for this is that microbes respond to strong sunlight
in the same way that my pale Celtic skin responds to sunlight.
My outer membrane gets all red, damaged and angry.
And for the bacteria, there are repair mechanisms
but they don't work quite so well as the water temperature increases
due to the green house effect inside the bottle.
So they get a double whammy.
Really bad sunburn and a slow pasteurization.
Once I had convinced myself or reassured myself that solar disinfection works,
we went to communities and tried introducing it there.
And what we found was diarrhea in infants reduced by 34%.
You might be saying to yourself, "Hmm, 34%, why isn't it 100%?"
Water isn't the only source of infection.
You'd have to introduce sanitation and hygiene as well.
We found children who were using solar disinfection for 12 months in Kenya.
They ended up 1 centimeter taller than kids who had not.
So there's a child development improvement.
Even though they all started off at the same height.
We were doing a study in Kenya when there was an outbreak of cholera.
The Department of Health immediately put all the emergency interventions in place.
But we went back afterwards to see whether there had been any
protective effect from solar disinfection.
And we found kids who were using solar disinfection
were 7 times less likely to get the infection.
So let's think about cholera for a moment.
Cholera is a fantastic disease. The symptoms are acute watery diarrhea.
You have a continuous stream of pale liquid from your GI tract.
The WHO has invented special cholera beds with a hole underneath
that you put a bucket underneath to catch what they call the rice water stools.
You die from dehydration.
If you are a healthy adult, you die within about maybe 2 days.
If you're an infant, you die in under 5 hours.
If we think of the 2,000 people in the room here today,
if you were all infected,
only about 20% of you would display those symptoms.
You'd all go home and infect the rest of your family.
But only 20% of you would experience the symptoms.
And if you remained untreated 5% of you would succumb.
And that's more or less the first 4 rows.
I'm sorry, you're dead. (Laughter)
Not my fault. You should have used solar disinfection.
If you use solar disinfection
the number who display symptoms comes down to 1/7th.
So instead of 400, we've got 54.
And that would give us about 14 deaths rather than 100.
So very effective against cholera.
In Cambodia we found it's very effective against dysentery.
Dysentery again is a life-threatening disease for the very young,
the very old and the immunocompromised.
And when we introduced it to primary schools in Uganda very recently
we found that the rate of absences in the kids
reduced from 2 days per child per term to 0.2.
So think about it, solar disinfection,
you're using plastic bottles that have been discarded.
You're using free available sunshine.
There's a child benefit. Child health benefit.
Child development benefit. A child education benefit.
Also there's a financial benefit because the parents or the guardians
are not paying for medicine for sick children.
You're not paying for transport to bring very sick children to the clinic.
And the caregivers are not missing out on income generating opportunities
because they're looking after sick kids.
In fact we very often find promoting water treatment
on the basis of improved family finances is more effective
than promoting it on the basis of improved family health.
An obvious question is you're putting water into plastic bottles.
You're putting plastic bottles in the sun. Is that safe?
That was a concern we've had all the way through.
And we've done various experiments looking for
chemicals leaching from the plastic that might create some kind of a hazard.
And we've found no evidence of these.
We've done studies in the European solar research facilities.
And 6 months of studies, there's not sign of them.
So we always say, "Replace your bottles after 6 months."
Not because anything goes wrong with them.
We just don't know what happens after 6 months.
So what next?
Recently I was in Ethiopia doing the same kind of thing but in the villages.
And the difference between you and them is half of the audience were armed.
There was a gentleman in the back who had a very spectacular rifle.
(Laughter)
And he asked me a question and I found experience has taught me:
always listen carefully to the man holding a gun when he asks you a question.
And he said:
"These 2-liter bottles, where would we get those?
What we have are 20-liter jerry cans. Why can't we use those?"
Well you can't use them because they're not transparent. They're opaque.
But that got me thinking.
I came home and we were standing around the water cooler, thinking:
"Could we think of a large-volume, (Laughter)
transparent container that we could use for solar disinfection?"
No, no we can't think of it.
And then my post-doc kind of slapped me over the head.
We're that kind of group.
And the answer was right within arms reach.
So we've done this where we've used water cooler bottles in the schools in Uganda.
And they're as effective as 2 liter bottles.
Today solar disinfection is accepted as an effective
intervention against waterborne disease.
It's accepted by the World Health Organization, by UNICEF.
It's in use by more than 50 countries throughout the developing world.
And it's used by 6 million people for their daily water needs.
But remember I said
that about 780 million people don't have access to safe drinking water.
So solar disinfection is by far the least frequently used water treatment.
And you have to ask yourself, "Well why is that?"
Well, it's nothing to do with the science.
The science we've proven time and time again. It works wonderfully.
It's more a psychological, a sociological, an anthropological problem.
If I just drive into a village that has bad water,
and I say I have the solution to your problem,
and I go to my jeep and I bring out a plastic bottle,
a used plastic bottle, that's a hard sell.
So what you have to do is you have to go in a very culturally sensitive way.
You've got to use local representatives who act as advocates for the technique.
And sometimes, the strategies you use in one country
will be different to an adjacent country.
The strategies that are effective in one region
will be different than in another region.
Because ultimately I'm trying to convince you that -
that's the solution to your problem.
I'm trying to say: "That water doesn't look safe.
Well it doesn't look clean.
But I'm trying to convince you that the water is safe."
And sometimes you have to do some of the strangest things
to convince people that you know it is safe.
(Gargling) (Laughter)
Just in case you thought I was faking it.
(Laughter)
So as you sit there and you wonder,
"Can I afford to pay my water charges this autumn?"
(Laughter)
I'd like you to think about the 800 million people who are asking:
"Can they afford not to treat their water?"
Thank you very much.
(Applause)