How clean does handwashing water need to be to still provide a benefit? - Risk-Based Assessment of Impact of Microbial Water Quality on Handwashing

  • tjulian
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How clean does handwashing water need to be to still provide a benefit? - Risk-Based Assessment of Impact of Microbial Water Quality on Handwashing

Hi Everyone,

I wanted to share our recent work looking at the impact of microbial water quality on handwashing effectiveness. We were attempting to answer the question: how clean does handwashing water need to be to still provide a benefit?

To answer the question, we looked at two scenarios:
  1. What is the impact of fecal contamination in handwashing water on the net change of fecal contamination on hands?
  2. What are the infection risks from hand-to-mouth contacts after washing with contaminated water?

We found that:
  1. Contaminated hands that wash with water with <1000 E. coli/100 ml will likely (>99.9%) reduce fecal contamination on hands by washing hands. Therefore, handwashing with contaminated water - unless it is grossly contaminated - will likely provide a net benefit
  2. Howevver, there is a non-negligible risk of infection from handwashing with contaminated water, even if the pathogen concentrations are very low. Therefore, to eliminate infection risks from handwashing water, the quality would need to be the same as drinking water

Our findings suggest that in the majority of communities, water quality should be sufficient for handwashing such that handwashing provides net overall benefits. However, in areas with grossly contaminated water supplies, water quality treatment interventions are likely needed alongside investments in infrastructure and/or behaviour change. Ultimately, decisions on treating and monitoring handwashing water quality need to be made within the larger context of development needs.

This discussion here is a summary of that described in further detail in both the Policy Brief here PDF , and the research publication here HTML ("Safely Managed Hygiene: A Risk-Based Assessment of Handwashing Water Quality")

I welcome your questions or other thoughts.

Thanks,
Tim

I am the Group Leader of the Pathogens and Human Health Research Group in the Dept. of Environmental Microbiology at Eawag, Swiss Federal Institute of Aquatic Science and Technology. Our group's research focuses on understanding and interrupting the environmental transmission of enteric pathogens and antimicrobial resistant bacteria. We integrate field sampling, laboratory experiments, and exposure and risk modeling to help elucidate the importance of traditionally neglected transmission pathways (for example, surfaces, soils, and hands).

Our group's research can be found on our homepage...
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Re: How clean does handwashing water need to be to still provide a benefit? - Risk-Based Assessment of Impact of Microbial Water Quality on Handwashing

Hi Tim,
Thanks for sharing your policy brief and paper here. I like how you are researching some very practical aspects about handwashing (also evidenced by your previous posts)!

I am interested in the bigger project that this research falls under, could you tell us a bit about that? Your forum profile is bare so I can't glean anything from that but I take it from the paper that you work at EAWAG. How is this work funded?

Kind regards,
Elisabeth

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  • tjulian
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Re: How clean does handwashing water need to be to still provide a benefit? - Risk-Based Assessment of Impact of Microbial Water Quality on Handwashing

Hi Elisabeth, thanks for following up. The work is funded through a combination of funding from Eawag, EPFL, and the Swiss National Science Foundation (SNF). Our work focuses on environmental transmission processes that drive infectious diseases. The SNF project focused on the role of soil in cycling of pathogenic E. coli in households, and published a few other papers based on field research in Bangladesh and Zimbabwe. If you are interested, the project metadata are available here: p3.snf.ch/project-157065

Thanks for the hint about the profile! I have updated it accordingly.

Best,
Tim

I am the Group Leader of the Pathogens and Human Health Research Group in the Dept. of Environmental Microbiology at Eawag, Swiss Federal Institute of Aquatic Science and Technology. Our group's research focuses on understanding and interrupting the environmental transmission of enteric pathogens and antimicrobial resistant bacteria. We integrate field sampling, laboratory experiments, and exposure and risk modeling to help elucidate the importance of traditionally neglected transmission pathways (for example, surfaces, soils, and hands).

Our group's research can be found on our homepage...
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