SaniPath - Assessment of Fecal Exposure Pathways in Low-Income Urban Settings (Emory University, USA) - and appeal to SuSanA members for input

  • joeturner
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Re: SaniPath - Assessment of Fecal Exposure Pathways in Low-Income Urban Settings (Emory University, USA)

Dear Suraja, can you give us a bit of context on how the SaniPath tool will be used? They collect samples to analyse for E.coli, but what does the tool tell them? Is it to be used to identify the most important health or hygiene risks in the community?

I have been watching this video from your website, which is very interesting but does not seem to explain much about using the tool

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  • sjraj
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Re: SaniPath - Assessment of Fecal Exposure Pathways in Low-Income Urban Settings (Emory University, USA)

Hi Joe, thanks for your message. That is an excellent question, and I apologize that it wasn't clear in the original post. After samples and surveys are collected, the data are combined along with other parameters from the literature, such as intake volumes and duration of exposure to characterize risk of exposure (see diagram below). The output of the tool allows people to compare the relative risks of exposure for different pathways. For example, if you are looking at open drains, produce, and piped water, the tool would allow you to be able to rank the risks relative to each other. The output also allows users to understand what is contributing more to the risk- frequency of exposure or dose (a combination of contamination level and intake values from the literature). Our goal is that the tool can be used to prioritize investments/programs based upon which pathways pose the highest environmental risk. We want to encourage users to think of upstream interventions that can help intercept the exposure (for example, covering open drains) or decrease contamination (chlorinating piped water at the municipal level). Currently, we are focused on pathways in the public domain that we believe to be most actionable by municipal governments and policy makers. I hope that helps to answer your questions. Let me know if you have any other questions or comments. We are always looking for ways to improve upon the tool.

-Suraja



Suraja Raj, MPH
Program Associate
Center for Global Safe Water
Rollins School of Public Health-Hubert Department of Global Health
Emory University
1518 Clifton Road, NE
MS: 002-7BB CNR 6040F
Atlanta, GA 30322
Tel:+001-404-727-5977
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  • joeturner
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Re: SaniPath - Assessment of Fecal Exposure Pathways in Low-Income Urban Settings (Emory University, USA)

Thanks, that's helpful. In the example of the "risk of exposure from three pathways in one neighbourhood for adults" graph in your first post, might a government use the tool to prioritise exposure from the produce rather than the drains?

I think your worker in the video I posted was mentioning that the soil around the school and even the school desks were highly polluted - so I'm guessing a similar analysis had been used to show that these were areas to address to reduce infection rates.

One thought I had was around variability of the sampling - and chance effects. If a municipality used the tool and found that the school soil (for example) was an area to prioritise, it might set in place a policy to reduce that risk. If it then reanalysed using this tool, is it possible that a sample with low E.coli rates could be seen as a 'success' - when in reality it was just accidental? Or alternatively maybe the particular desk where a single child was sitting was particularly contaminated, whereas the others were cleaner. How robust is your tool to these kinds of variations?
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  • sjraj
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Re: SaniPath - Assessment of Fecal Exposure Pathways in Low-Income Urban Settings (Emory University, USA)

Yes, in the example graph that I posed with the three pathways, it would be reasonable to expect that a user of the tool may choose to prioritize exposure from produce over that of drains. You can see from the graph that what is driving this greater relative risk is really the frequency of ingestion of produce (in Ghana where this data is from, consuming raw produce is common) as opposed to frequency of exposure to drains (which may be accidental and relatively rare).

Variability is definitely an issue- particularly when we deal with limited samples and survey sizes, and as you mentioned sampling variability/chance effects. In an effort to stay simple, this first version of our tool's analysis calculated risk of exposure using point estimates, which do not take into account variability. However, we recognize that variability is a concern and we are currently working on utilizing the distribution of sample and survey data so that variability can be better accounted for.

Suraja Raj, MPH
Program Associate
Center for Global Safe Water
Rollins School of Public Health-Hubert Department of Global Health
Emory University
1518 Clifton Road, NE
MS: 002-7BB CNR 6040F
Atlanta, GA 30322
Tel:+001-404-727-5977
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Re: SaniPath - Assessment of Fecal Exposure Pathways in Low-Income Urban Settings (Emory University, USA)

Dear Suraja,

This might be a stupid question but could you please explain to me how QMRA* relates to your Sanipath tool, i.e. is Sanipath an application of QMRA or an extension (or simplification) of it?
You mentioned QMRA once in your project description under objectives:

o Conduct an exposure assessment and quantitative microbial risk assessment (QMRA).


Thanks,
Elisabeth

* QMRA = Quantitative Microbiological Risk Assessment, see also: en.wikipedia.org/wiki/Quantitative_Micro...ical_Risk_Assessment

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  • YWAN446
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Re: SaniPath - Assessment of Fecal Exposure Pathways in Low-Income Urban Settings (Emory University, USA)

Dear Elisabeth,

I work as a biostatistician/data analyst in SaniPath group. I hope I can answer your questions about QMRA.

The QMRA wiki website qmrawiki.canr.msu.edu/index.php?title=Qu...sessment_(QMRA)_Wiki summarizes some concepts about QMRA. On this website, QMRA was defined as a framework and approach that brings information and data together with mathematical models to address the spread of microbial agents through environmental exposures and to characterize the nature of the adverse outcomes. As far as I understand, using quantitative data (microbial and behavioral) and mathematical models distinguishes QMRA from traditional risk assessments . As for the mathematical models and calculations, they don’t have to be as complex as Bayesian Analyses or Monte Carlo Simulations. They could be as simple as multiplying frequency of behavior and dose per contact together.

SaniPath is an application of QMRA. However, since our goal for SaniPath is to provide overall fecal microbe exposure information instead of information specific to one pathogen, the SaniPath methodology doesn't use a dose response model, which must correspond to one specific pathogen. Therefore, the SaniPath methodology functions as an exposure assessment rather than an estimate of the probability of infection.

An exposure assessment is a two part process that includes 1) evaluation of pathways that allow microorganisms to be transported from the source to the point of contact with human beings and 2) estimation of the amount of exposure that is possible between humans and contaminants. Conducting a realistic exposure assessment is important for good risk characterization as well as risk management. (ref: qmrawiki.canr.msu.edu/images/Introduction.pdf )

The SaniPath exposure assessment for the Phase 1 in-depth analysis tracks back the source of fecal microbes that enters the human body and estimates its amount using a huge Monte Carlo Simulation. The microbial and behavioral data are all based on distributions, which are estimated using Bayesian Analysis. We can provide more detailed information about our exposure assessment after our exposure paper is finished.

Thanks,
Yuke (Andrew) Wang

Yuke Wang, MSPH
Data Analyst
Emory University
Rollins School of Public Health–Hubert Department of Global Health
Center for Global Safe Water
1518 Clifton Road, NE
MS: 002-7BB CNR6040B
Atlanta, GA 30322
Phone: 404-727-2238
Fax: 404-727-4590
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Re: SaniPath - Assessment of Fecal Exposure Pathways in Low-Income Urban Settings (Emory University, USA)

Hi Joe,

I can explain in some more detail how the SaniPath analysis is planning to deal with the issue of sample variability.

The SaniPath study has three phases so far (Phase 1, Phase 1.5, and Phase 2). Right now we are working on a methodology to incorporate the variability from samples into our results. We have used phase 1 data, which has a larger sample size, to decide what types of distributions the environmental concentrations and frequencies of behavior follow. In order to see how robust a sample size of 10 was for each pathway, we used the bootstrap method and found that the variance of the mean of the log 10 concentrations for ten random samples was small. This enabled us to compare pathways on a log 10 scale. In order to prioritize pathways, we don't need an accurate estimate of the dose for each pathway, we just need the ranking. Since our goal is to distinguish 100 from 1000 rather than 20 from 50, ten samples are enough. Currently, we are conducting more analysis and trying to use a larger sample size for those pathways with a larger variability to increase the accuracy and robustness.

Furthermore, Bayesian Analysis ( en.wikipedia.org/wiki/Bayesian_inference ) can be used to estimate the distribution of both the environmental concentration and frequency of behavior, which account for variability. For example, if you sampled from the distribution and you had one accidentally highly contaminated sample while others were very clean, our new output could tell us that most of time this pathway is clean, but that there is a small probability that it could be very contaminated. This should be a good estimate of reality. If we sampled from the distribution again and we got ten samples that were all very clean, we could get results similar to the first time given the assumptions about the distribution. Though we didn't pick a highly contaminated sample the second time around, the distribution assumption can still inform us that there is a very small probability of getting a highly contaminated sample. Our results would depend on both the assumption of the distribution, which comes from our larger SaniPath phase 1 study, and the data people collect when they use the tool. I hope this helps answer your question about how our tool is trying to deal with chance variability.

Thanks,
Yuke (Andrew) Wang

Yuke Wang, MSPH
Data Analyst
Emory University
Rollins School of Public Health–Hubert Department of Global Health
Center for Global Safe Water
1518 Clifton Road, NE
MS: 002-7BB CNR6040B
Atlanta, GA 30322
Phone: 404-727-2238
Fax: 404-727-4590
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Re: Appeal to SuSanA members for input

We'd like to make an appeal to Susana members for input on the following:

A. Suggestions about where we can deploy the SaniPath Rapid Assessment Tool?
We're looking for 1) partners working at the city level interested in deploying tool to inform sanitation interventions, 2) partners who can use this type of data to inform their work, and 3) institutions that would be good candidates to learn to use the tool.

B. Suggestions for candidates for the advisory committee?
We're are in the process of assembling an international advisory committee that can provide input on the following questions:
1) What are the greatest challenges facing sanitation decision makers?
2) What scale are decision makers most interested in (city vs. neighborhood level)?
3) How can we best engage potential users of the tool?
4) How can we best convey risk results visually?
5) How can we facilitate the translation of the tool recommendations into actionable interventions.

We welcome and thank you for your input!
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Re: Appeal to SuSanA members for input

Katharine's appeal from 24 August didn't lead to any responses yet, so I thought I would give you this additional background information:
Katharine presented about Sanipath, and about her appeal to SuSanA members, at the SuSanA meeting in September:
See here: www.susana.org/en/events/susana-meetings...na-meeting-stockholm

Using the Control+F function you will find her presentation:

Katharine Robb (Emory University): The SaniPath Rapid Assessment Tool:Assessing Public Health Risks from Unsafe Fecal Sludge Management in Poor Urban Neighborhoods
www.susana.org/images/documents/04-meeti...t_Tool_Session_4.pdf

See the video of her presentation here:


Or go to time 14:47 here:


Regards,
Elisabeth

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  • SDickin
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Re: SaniPath - Assessment of Fecal Exposure Pathways in Low-Income Urban Settings (Emory University, USA) - and appeal to SuSanA members for input

Dear Sanipath team,
This is a really interesting project. I previously met Katherine at WWW but it is very helpful to learn more about all the different aspects of the work in this thread.

I recently reviewed research on wastewater irrigation and health risks ( ehp.niehs.nih.gov/15-09995/ ), and one of the findings was that other exposure pathways (e.g. WASH, use of animal manure) were frequently ignored in these studies, which provides an incomplete picture. A gap it seems like SaniPath can address!

Another finding of this review was that there was little work examining different exposures during the farm to fork pathway. In the Sanipath case, I guess that only the end-product 'produce' would be assessed, but being able to compare farm level, transport/handling or marketplace contamination (washing of produce with contaminated water) could allow more targeted actions. Perhaps a targeted path could be developed to examine the greatest risk pathway in finer detail.

Do you see any potential for expanding beyond urban areas. During some research fieldwork in Uganda I observed that peri-urban or even 'rural'areas nearby towns were growing rapidly and poor planning of sanitation was occurring (and causing contamination of water resources with impacts on downsteam communities). It would be interesting to develop the tool to inform planning in areas that are rapidly growing like this.

best regards,
Sarah

Dr. Sarah Dickin,
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Stockholm Environment Institute
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Re: SaniPath - Assessment of Fecal Exposure Pathways in Low-Income Urban Settings (Emory University, USA) - and appeal to SuSanA members for input

Dear Sarah,

Thanks so much for your message and apologies on the delay in getting back to you!
Thanks for bringing up the important point regarding wastewater irrigation and health. One of the key findings from the in-depth SaniPath study in Accra was that the dominant pathway of exposure to fecal contamination for young children was through the food supply. This has important implications for the WASH sector – that typically ignores food safety. As you point out, urban agriculture is a key contributor to the food supply in many cities, and wastewater irrigation is a common practice. Our study demonstrates that this pathway for exposure combines high frequency of exposure and high “doses” of fecal contamination – making it a high-risk pathway that should be a priority for intervention. We’ve recently submitted a manuscript by Wang et al. detailing this finding to the American Journal of Tropical Medicine and Hygiene and we can send you a copy once it’s published. We also conducted a sub-study lead by a PhD student at the London School of Hygiene and Tropical Medicine, Prince Antwi-Agyei. The results of that work can be found in a journal article entitled “A Farm to Fork Risk Assessment for the Use of Wastewater in Agriculture in Accra, Ghana” ( journals.plos.org/plosone/article?id=10....journal.pone.0142346 ).

Regarding your question about applying SaniPath in rural or peri-urban areas, we’ve put some thought into this in the past but don’t currently have plans to develop a version of the tool for rural areas. However, we do have plans to apply the tool in peri-urban areas and smaller towns where sanitation investments are planned through a partnership with EAWAG.

We've also recently circulated a policy brief on public toilets based the SaniPath study in Accra, Ghana ( sanipath.org/wp-content/uploads/2016/04/...rin-Policy-Brief.pdf ) that may be of interest.

We really value you taking the time to contact us and for sharing your insights! Please do keep in touch!

Kate

Katharine Robb, MPH
Associate Director, Research Projects
The Center for Global Safe WASH
Emory University
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Re: SaniPath - Assessment of Fecal Exposure Pathways in Low-Income Urban Settings (Emory University, USA) - and appeal to SuSanA members for input

Dear Kate and SaniPath team!

One year on from your last post I am just wondering if you could update us with further developments regarding your SaniPath tool? For example, could you tell us more about this:

However, we do have plans to apply the tool in peri-urban areas and smaller towns where sanitation investments are planned through a partnership with EAWAG.


Furthermore, which are your current countries of interest? Is it still Ghana as you had indicated in your last post?

There is so much going on in Ghana regarding sanitation improvements, really encouraging to see .. (e.g. here on the forum lately about behavior change: forum.susana.org/5-community-led-approac...-question-from-ghana and about composting and reuse of fecal sludge: forum.susana.org/98-resource-recovery-fr...n-to-feed-the-nation )

Regards,
Elisabeth

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