[Stoves] health impact follow-up

Paul Anderson psanders at ilstu.edu
Fri Sep 5 11:12:11 CDT 2014


Marc,

I am delighted to see your involvement with these stove issues. (To 
all:   Marc and I go back many years with earlier TLUD work!!   He is a 
great asset for the efforts!!)

I am also please to be able to (I think) point out an error in your 
calculations (helps some, but does not resolve the major issue, still 
being discussed).   Marc wrote:
>
> *Conclusions: just how small?*
>
> We can do a back-of-the-envelope analysis to tell the story of the 
> numbers presented here. If we assume six billion people use primitive 
> stoves, then one hundred million of them is 1/60 of the total. 1/60 of 
> the four million deaths worldwide is ~67,000. Rocket stoves would save 
> 20% of those lives according to the exposure-response model: just 13,400.
>
> So, you get out 100,000,000 stoves, and you save 13,400 lives. This 
> also assumes that you achieve the PM emissions reductions in practice. 
> There are mountains of evidence (academic and practical) that this is 
> not the case. 
The error is assuming 6 billion people use primitive stoves. Actually, 
about 3 billion would be a useful number.    And those people are living 
in HOUSEHOLDS, in which perhaps 6 people have food cooked on one 
stove.   That would be 500 million households needing seriously improved 
stoves.    That changes your calculations.   If you agree with me, 
please redo your calculations and send again.

Commentary:   The highly worthy goal of the GACC to "deliver" 100 
million improved stoves by 2020 would accomplish the stove task for 20% 
(or 1/5th) of the needed stoves.   And we have MUCH work to do just to 
reach that 100 million goal.   Thank goodness we have started the 
efforts.   And I suspect that we (the world wide efforts) could make it 
by 2020.

But of those in need, that leaves 80% not reached.   And the initial 20% 
could probably be the easiest 100 million households to reach.  Simply 
stated, those who do stove efforts are truly challenged by the magnitude 
of the task.

AND we are faced with the issue that the stoves are NOT performing well 
enough to have the desired impact on health.   (Favorable Impacts 
regarding deforestation / environment habitat for endangered species, 
and job creation and carbon balance issues / CO2 / black carbon, etc, 
etc. etc. are important and are also forces that stimulate the stove 
efforts, BUT we are discussing mostly the health issues.).

 From the health data (ala Kirk Smith and others) that is shown in the 
graph that Marc provided with his comments, there is an important gap 
between the CURRENT BEST of biomass-fueled stoves and the DESIRED low 
level of emissions (represented by the LPG stoves, and electric 
stoves.).   Current best (as labeled) are stoves with fans, better 
states as FA for Forced Air or Fan Assisted.   Well, perhaps SOME stoves 
that have fans could be low in emissions.   Simply having a fan does not 
make a stove perform well.

 From the health perspective, it seems unlikely that ND (Natural Draft) 
stoves are going to have emissions low enough for the desired health 
impacts.   Even ND stoves that attain Tier 4 ratings (in laboratory 
tests) still need to be used correctly by the households.  Very 
challenging!!!!!!!

Let's see some replies.  I am quite happy to have others show that I am 
not correct.

Paul

Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com

On 9/5/2014 12:23 AM, Marc-Antoine Pare wrote:
>
> Hi everyone,
>
> Thanks for the discussion so far. I've looked at the health numbers 
> for improved cook stoves in some more detail.
>
> I found two major approaches to quantifying the impact on health by 
> stoves: long term studies and modeling based on exposure response.
>
> They both point to the same overall conclusion: improved biomass cook 
> stoves will only reduce a small number of the "4 million deaths" you 
> hear about from indoor air pollution.
>
> Also, it appears that there isn't an existing biomass technology that 
> will!
>
> Please bear in mind that this is just a few days of compiling results 
> from research. All of these conclusions are tentative. I welcome any 
> and all criticism. The reading has been quite educational so far.
>
> One note at the start: the studies here consider the negative effects 
> on respiratory health by particulate matter (PM). The studies I read 
> note that this is by far the largest contributor to the burden of 
> disease from indoor air pollution.
>
>
> *Long-term studies*
>
> /Effect of reduction in household air pollution on childhood pneumonia 
> in Guatemala (RESPIRE): a randomised controlled trial (2011)/
>
> 523 households involved. About half get an improved plancha stove, 
> which reduces exposure about 50%. Eighteen months later, there was a 
> 22% reduction in cases of pneumonia.
>
> Note that in this population, there were 9 deaths attributed to 
> pneumonia. This is important later.
>
> Also important to note is that aid workers regularly coached these 
> households in usage and maintenance.
>
>
> /A Recipe for Success?**Randomized Free Distribution of Improved 
> Cooking Stoves in Senegal/
>
> 98 households get a stove for one year. Respiratory disease symptoms 
> for cooking women drop by 8%.
>
> /
> /
>
> /UP IN SMOKE: THE INFLUENCE OF HOUSEHOLD BEHAVIOR ON THE LONG-RUN 
> IMPACT OF IMPROVED COOKING STOVES/
>
> 5 years, 15,000 Indian households (!) "We find no evidence of 
> improvements in lung functioning."
>
> The critique of this study is that they used mud stoves with chimneys 
> that weren't all that clean-burning.
>
> *What the long-term studies tell us*
>
> I was surprised that the number of stoves required to impact health 
> was so high. In the Guatemala study, you need 250 stoves to prevent 
> about 10 cases of pneumonia.
>
> Another interesting thing to note is that I didn't find any studies 
> that monitor big enough populations for long enough to quantify how 
> many /deaths /are prevented by improved stoves. Again, in the 
> Guatemala study, the stoves saved somewhere between 1-5 lives. This 
> number is so small that it's really tough to extrapolate it at all.
>
> Clearly something funny is going on here. Why exactly are the numbers 
> so small? Did people use the stoves incorrectly? Would better stoves 
> have helped? And why did nothing happen in India?
>
> One approach to answering these questions is to dig in to the 
> mechanism for saving lives with stoves. We do this with the exposure 
> response to pollutants.
>
>
> *Modeling based on exposure-response*
>
> Health impact from exposure to PM is well studied. Exposure amount 
> predicts quite accurately future health problems. This is great 
> because it let's us start answering the question: just how clean do 
> stoves need to get to meaningfully impact health?
>
> We can really get into a lot of detail here. It's a dissertation's 
> worth of calculation to come up with these numbers (see: THE 
> DEVELOPMENT OF NUMERICAL TOOLS FOR CHARACTERIZING AND QUANTIFYING 
> BIOMASS COOKSTOVE IMPACT)
>
> Kirk Smith presented a summary of what exposure-response can tell us 
> about stoves at the Clean Cooking Conference just this May.
>
> Here's the graph:
>
> [attached]
>
> The key note is that a rocket stoves "leaves ~80% of the burden [of 
> disease] untouched". That means that even if we give everyone a rocket 
> stove, only 20% of the 4,000,000 deaths from IAP will be affected.
>
> Here's the reasoning. The red line in the graph is called the 
> "exposure-response relationship". It's a log-linear relationship. That 
> means that most of the damage from PM exposure occurs from zero 
> exposure to a very small amount of exposure.
>
> It turns out that improved cook stoves -- even the very fancy fan 
> stove developed by Phillips -- don't reduce emissions below that 
> initial amount of very dangerous exposure.
>
> Kirk Smith provided this summary in London: "Current Health Evidence 
> shows now that even major reductions (<90%) in emissions still lead to 
> small health improvements"
>
>
> *Conclusions: just how small?*
>
> We can do a back-of-the-envelope analysis to tell the story of the 
> numbers presented here. If we assume six billion people use primitive 
> stoves, then one hundred million of them is 1/60 of the total. 1/60 of 
> the four million deaths worldwide is ~67,000. Rocket stoves would save 
> 20% of those lives according to the exposure-response model: just 13,400.
>
> So, you get out 100,000,000 stoves, and you save 13,400 lives. This 
> also assumes that you achieve the PM emissions reductions in practice. 
> There are mountains of evidence (academic and practical) that this is 
> not the case.
>
> I am trying to find what I am missing here. I really expected the link 
> to be much more clear and significant. Is there some other reason that 
> stoves are promoted besides health benefit? Is there some overarching 
> strategic goal that I'm missing?
>
> Really, I'm looking for some number to tell the story. All the numbers 
> I have found point to the fact that stoves, even the very best ones we 
> have, won't move the needle on deaths from IAP.
>
> I would be very happy to be wrong about this. I know that development 
> issues can be confoundingly complex, and I would welcome another 
> perspective on this.
>
> One silver lining to all of this is that I think it would be great for 
> technology developers to hear that current technologies are totally 
> inadequate. There's nothing like an impossible challenge to galvanize 
> the inventor :)
>
> - Marc Paré
>
>
>
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