Hi Elisabeth,

sodium hydroxide is caustic soda or lye. Lye dissolves greases. White wood ash contains potassium carbonate, or potash, along with calcium hydroxide, but very little if any sodium hydroxide. By adding water to white wood ash, the calcium hydroxide and potassium carbonate react, forming caustic potash (ash lye, potassium hydroxide) and calcium carbonate (please somebody correct me if I'm wrong, I'm not a chemist!).

On this basis I have always assumed that handwashing with ash and water means handwashing with ash lye. I wash my hands with wood ash, which is particularly effective at removing greases and hard-to-remove dirt. Ash will remove just about anything from hands, and it certainly is not painful to use and it doesn't burn skin. Well, not mine anyway...

I'm asking whether it's appropriate for people from the developed world who like the smell and feel of soap to impose their paradigms on those with different practices...  Habits are also influenced by tradition and availability. If someone washes their hands effectively with wood ash and has always done so, because they are happy with that practice and use their own resources, is it right for someone to come along and say "you should use soap, it will feel nice on your skin and make you smell nice."?

cheers
Dean

Thanks for the interesting forum posts. The word "lye" was new to me and I had to look it up. If others also didn't know what it is, here is a quick result from Google search:
Turning your wood ash into lye for soap making

It says there:

Lye (sodium hydroxide) is formed when wood ash (which is mostly potassium carbonate) is mixed with water. The mixed solution is extremely alkaline and if it comes in contact with your skin, it begins to absorb the oils and turns your skin into soap. It's pretty painful so before I ever begin, I make sure that I have vinegar nearby to neutralize the burn if the solution does happen to come in contact with my skin. I also wear rubber gloves and goggles in case there is any splash back during the mixing process.

I have the feeling that there is confusion in some of the statements: the original question was about handwashing with ash. Handwashing with ash lye is a bit different, isn't it? If ash lye is used to make soap (like that article above explains) then it's a different story again.

I do wonder how widespread the handwashing with ash or ash lye is these days. Is it only practiced in rural areas where people cook with firewood, or also in more urban areas (people cooking with coal?)). Is it common?

Furthermore, Dean wrote: 

Sian Whites statement "handwashing with ash does not feel very nice and does not leave hands feeling and smelling nice in the way that soap does" do not help either. Advice should be authoritative and objective.

I disagree with Dean and find that Sian's statement is perfectly valid. Handwashing has a lot to do with habits, and habits are influenced by feelings, smells, aspirations and so forth.  So if handwashing with ash becomes a deterrent to handwashing at all then we have a problem. 

Regards,
Elisabeth

When growing up in rural Kenya we were always advised to use hot ash for disinfecting latrines. The high temperature played some role in killing the pathogens. Hot ash, though, shouldn't be used to wash hands as it can lead to burns. Cold ash may do due to the high pH. Caution should, however, be taken to avoid bruising hands with the coarse particles by applying the ash directly to hands. The best approach would be to mix the ash with water in a bucket and allow it to settle. After settling, clean  water can be decanted and used for washing hands.

Coronavirus are wrapped in a lipid (oil) envelope, therefore ash lye should be just as effective as soap at breaking this down. Not sure why Sian White would assume that ash only works by abrasion. The lye in ash dissolves oils and being a concentrated alkali is also a disinfectant. Perhaps a chemist could chip in to this discussion?

Juan Smulders states that "ash can kill germs (less effectively than soap of course)". Noting how caustic ash is, it should be far more effective than soap at disinfecting. Juans statement comes across as a subjective impression. Sian Whites statement "handwashing with ash does not feel very nice and does not leave hands feeling and smelling nice in the way that soap does" do not help either. Advice should be authoritative and objective. For example: Handwashing with ash does not bear the risk of contracting soil-transmitted pathogens unless contaminated soil is mixed with the ash.

Exposure to heavy metals in the ash depends on the particular timber treatment used. Chrome-copper-arsenic treatments will leave arsenic, chrome and copper in the ash (heavy metals). But these are not cadmium, mercury or lead oxides, and I very much doubt that washing hands with the resulting ash will cause an accumulation of arsenic, chrome or copper in the body. I'd be more worried about exposure from the fumes when burning CCA treated wood. Then there is creosote treatment (e.g. in railway sleepers). This will not remain in the ash and although the smoke might contain some toxins resulting from incomplete combustion, the ash will not contain toxins or heavy metals. Then there is boron treatment, which will result in ash containing small quantities of boron. Even better for washing hands and with no consequence. Generalisations that "treated" timber will produce toxic ash are not helpful.

cheers
Dean

Washing, cleaning, decontamination, and disinfection do not have equal meanings. Washing means exposure to cleaners. Specifically, water cleaning means removing physical and visible dirt, particularly with clean water. Decontamination means removing hazard agents, for example, cleaning the surface with water and detergent or soap.

Disinfection means removing infection agent by killing biological pathogen or removing chemical hazard agents or enabling them to cause a hazard and reproduce (biological) or removing by diluting (chemical).

About ash application ash a cleaner," Wood ash and natural lye have been widely used in villages for centuries as a cleaning material in the form of soaps by being mixed  with natural oils in certain amounts."    *
Wood ash can be directly used in its dry form for cleaning by scrubbing as well as in the form of lye through mixing it with water ".
Many of the cleaning products we use in our houses today contain chemically reactive and toxic ingredients. This is a big risk to take for the health of our bodies and our planet since we directly inhale these chemicals and they also pollutes the soil and water.

*  ecovillage.org/solution/wood-ash-as-a-na...l-cleaning-material/

 So ash could be a suitable alternative  (cleaner not disinfectant) when other cleaning agents are not available particularly in emergency situation or absence or shortage.

Mohammad

This brief from Sian White on the Hygiene Hub/ Covid19 website gives some guidance. 
resources.hygienehub.info/en/articles/39...QM6wVqX8F8IfHCa75ZhE

Can ash be used for handwashing? Topic brief

Ash can be used effectively for  hand cleaning in general . However, soap and water in combination are particularly effective for  killing and removing SARS-CoV-2  (see ‘ Why does handwashing with soap work so well to prevent COVID-19 ?). Ash is thought to remove germs from hands in a different way to soap - primarily through friction. It is unclear if ash would have the same effect as soap on the coronavirus as no studies have been done on this. 
However in settings where soap is really scarce handwashing with ash is likely to be more effective than handwashing with water alone. If recommending ash to households make sure that they are using the white ash from the centre of a fire once cooled. This white ash is likely to be the most sterile as it was heated at the highest temperature. Be aware that handwashing with ash does not feel very nice and does not leave hands feeling and smelling nice in the way that soap does, as such promoting ash may actually discourage people from practicing handwashing. We recommend also reminding people that soap of any type can be used for handwashing. See our section on ‘ Are some types of soap more effective than others? ’ for more information.
Recommendations:

• There is no evidence on the effectiveness of ash for removing or killing SARS-CoV-2. 
• In settings where soap is really scarce, remind people that any type of soap is effective for handwashing. 
• Where there are no other options, handwashing with ash should be encouraged as it is more effective than handwashing with water alone. 

Want to know more about COVID-19 and handwashing? 

• Why does handwashing with soap work so well to prevent COVID-19?
• Are some types of soap more effective than others?
• Should we be promoting handwashing with chlorinated water?
• What can we do where soap is scarce?
• Can soapy water be used?
• Is alcohol-based hand rub better than soap?
• Should we be promoting handwashing at different times during the COVID-19 outbreak?
• What can we do in areas with real water scarcity?
• Can I use greywater or water that is not clean for handwashing?
• Is it safe for people to share handwashing water?
• Do public handwashing facilities pose a risk?
• Can bar soap spread COVID-19?
• What kinds of handwashing facilities should we construct?
• How should hands be dried?

Here is another response by Mike Clarke that came in via the HIFA Dgroup:

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There is a Cochrane rapid review, podcast and Evidence Aid summary on the use of ash
for hand hygiene:

www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD013597/full
www.cochrane.org/podcasts/10.1002/14651858.CD013597
www.evidenceaid.org/hand-cleaning-with-a...fects-are-uncertain/

Best wishes,
Mike

Mike Clarke
Director, Northern Ireland Methodology Hub and Northern Ireland Clinical Trials
Unit
Research Director, Evidence Aid
Podcast Editor, Cochrane Library

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I copy the authors' conclusions from the rapid Cochrane review:

Based on the available evidence, the benefits and harms of hand cleaning with ash compared with soap or other materials for reducing the spread of viral or bacterial infections are uncertain.

Regards,
Elisabeth

I am copying a further reply by Alberto ACQUISTAPACE:

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Hi Erin and Emma,

According to " COVID-19 Emergency Response UNICEF Hygiene Programing
Guidance Note -Revision 1/4/2020 - sanitationandwaterforall.org/sites/defau...ng-guidance-2020.pdf " currently no evidence is available on the effectiveness of handwashing
with ash in the context of Covid-19. Generally, handwashing with ash is bears
the risk of contracting soil-transmitted pathogens and exposure to heavy
metals. Hence, handwashing with soap is preferred over handwashing with ash,
but the latter can be promoted as a last resort.

Also LSHTM discourages use of ash and promote soap ( globalhandwashing.org/resources/qa-diffe...lternatives-to-soap/ )
Hope to have been useful!

Alberto ACQUISTAPACE
Référent Technique Eau, Hygiène et Assainissement / WASH Technical Advisor
SOLIDARITES INTERNATIONAL| 89 rue de Paris 92110 Clichy, FRANCE
WebSite : www.solidarites.org

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And a response by Juan Smulders from the same e-Discussion on the RWSN platform:

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I am not sure youwill find a clear answer.
If you do not have soap, washing with ash is better than only water. Ash is
a basic with high pH and can kill germs (less effectively than soap
ofcourse).

It also creates friction to wash of dirt.
I would also like to share the newly create hygiene hub with a lot of
answers to questions and they even have a expert helpline to assist with
COVID related queries.
resources.hygienehub.info/en/articles/39...used-for-handwashing
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I am cross-posting this contribution from an e-Discussion about Covid-19 and WASH that took place in April 2020 on the RWSN platform (more information about that e-discussion here ).

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Posted by Emma Kelly (from UNC) on 15 April:
 
This is a response to the question by Erin Huber Rosen (Executive Directorand Founder, Drink Local Drink Tap) on 15 April:

Does anyone have research showing the proof that ash is effective in
cleaning to the standards needed for this virus and others? 

Hello Erin,

Thank you for your very relevant question about using ash as a hand washing
material. There is evidence that hand washing with ash (and sometimes even
sterilized soil) is effective in removing fecal indicator bacteria (FIB).
Studies in India (1) and Bangladesh (2), for example, found that washing hands
using ash was as effective as using soap. Both studies assessed this by
testing the quantity of FIB on the hands of participants post-washing.
A more recent study in Bangladesh found that washing with ash and water
reduced concentrations of FIB on hands, and that diarrhea was equally likely
for children of caretakers who used ash versus soap (3).

A review published by the International Scientific Forum on Home Hygiene
compiles some of the data available on the effectiveness of using ash to wash
pathogens off of hands (4). However, the review also discusses risks
associated with using soil or ash as a hand washing material, which may
themselves be contaminated with pathogens, helminths and heavy metals.

References quoted above:
(1) Anuradha, P., Devi, P.Y. & Prakash, M.S. Effect of handwashing agents
on bacterial contamination. Indian J Pediatr 66, 7–10 (1999). doi.org/10.1007/BF02752341 .

(2) Hoque BA and Briend A, Comparision of local hand washing agents in
Bangladesh. Jr Trop Med and Hyg 1991; 94 : 61-64.

(3) Baker, K.K., Dil Farzana, F., Ferdous, F., Ahmed, S., Kumar Das, S.,
Faruque, A.S.G., Nasrin, D., Kotloff, K.L., Nataro, J.P., Kolappaswamy, K.,
Levine, M.M., 2014. Association between Moderate-to-Severe Diarrhea in Young
Children in the Global Enteric Multicenter Study (GEMS) and Types of
Handwashing Materials Used by Caretakers in Mirzapur, Bangladesh. Am. J.
Trop. Med. Hyg. 91, 181–189. doi.org/10.4269/ajtmh.13-0509

(4) Bloomfield, S.F., Nath, K.J., 2009. Use of ash and mud for handwashing in
low income communities International Scientific Forum on Home Hygiene (IFH).

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It seems fair to say that there does not appear to be much evidence about the safety of handling ash. The nearest I could find (with reference to the potential dangers of heavy metals from wood ash) is this paper, which considered the dangers to workers in biomass powered power plants: www.degruyter.com/view/j/bimo.2015.2.iss...1/bimo-2015-0001.pdf

It seems that dermal metal exposure is a real issue however it seems to me that the risk to a worker in a power station would be expected to be several magnitudes higher than someone who was using the ash they produced from their own cooking.

Therefore I'd think that the important question is the potential risk of a dermal heavy metal dose from using ash compared to the potential benefits (and perhaps the risk of not using it, if there was no soap available).

The evidence as to the effectiveness of ash for handwashing seems mixed. See www.ajtmh.org/content/91/1/181.full

Cor posted the same question on Knowledge Point and he received the following interesting answer there today (knowledgepoint.org/en/questions/3285/is-...shing-with-ash-safe/):

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by Olmo Giovanni


Hello Dietvorst,

Ashes are used as an alternative to soap in cases the latter should not be readily available, or in case of emergency, its advantages are ash being common and easy to find item in rural settings, and providing almost as good pathogen removal in handwashing as soap.

Regarding your questions, it is difficult to provide a general answer, as the risk of being exposed to heavy metals almost always depends on the location, type of firewood used, and type of contaminant in the firewood.

As a rule of thumb, when burning contaminated wood (e.g. railway sleepers, or any other treated wood), the main pathways for exposure are the products of combustion by inhalation and dermal absorption, and by ingestion of contaminated drinking water or via bioaccumulation trhough the foodchain.

That said, skin absorption can still play a role in chronic toxicity, mostly through the exposure to contaminated soils or clays, albeit once again this changes dramatically depending on the type of hazardous substance dealt with.

This paper provides an overview of the typical exposure pathways for the most common (and dangerous) heavy metals: while dermal absorption is mentioned as a possible pathway in the general exposure dyagram, it is then not mentioned once in each heavy metal description for lead, mercury, arsenic, and cadmium. It is worth noting, however, that some forms of lead (tetraethyl lead) and mercury are more prone to absorption than other www.uic.edu/classes/pcol/pcol425/restric...Toxicity-M2-2011.pdf

A good review of H&S and exposure pathways is the NIOSH pocket guide to chemical hazards, covering all possible substances being employed in the US manufacturing and service industry. I'm afraid there is no firewood ash in it, but it will definitely include heavy metals

www.cdc.gov/niosh/docs/2005-149/pdfs/2005-149.pdf

So, to provide an answer to your four questions:

Ash may possibly be contaminated; the risk of absorbing heavy metals through handwashing is minimal compared to other exposure pathways; and I doubt there is a soap lobby pressuring for the use of soap, otherwise the ash reference would have never made it to the SDGs.

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