Hope all is well with you in the midst of semester and festive busyness. I see from your blog that your workshop was last Sunday, I hope that went splendidly!
I do not know if you would be able to spare the time for a favour, regarding the questions I sent you on 2 January. The reason being my unforeseen need to make an informed decision about the water filter by next Monday, given some circumstances that have arisen. My residence includes young occupants, so I hope to be as careful on this choice as I can too for their sake.
I am incredibly sorry for any trouble and inconvenience my request may cause to you; I am truly appreciative for your generous professional insights this while. Allow me to say how these have really enlightened my understanding and shaped my considerations to date. Would be extremely grateful to hear from you if you could, even if otherwise I do understand. Warmest wishes to you and all of yours always!
Here are the two questions again:
1. The Doulton filter (Sterasyl ceramic)
is silver-impregnated ceramic. I understand the purpose of the
silver is to disinfect and filter the drinking water. I expect that a
presumably (and hopefully) small but unknown quantity will invariably enter the
filtered water. I also read that silver is naturally-occurring around us... but
drinking it daily in the long run may be quite another matter. I drink about
2.5-3.0 litres of water a day on average. I'm concerned about the accumulation
of silver in the body, or if this taxes the kidneys/liver unduly.
So really – how safe is silver-impregnated water filter media for adults, infants and children? Or – in the best-case scenario – does the silver not leak into the filtered water at all? There may be scary consequences like argyria to consider for heavy water drinkers perhaps...
Some of the links I read on Silver:
http://www.who.int/water_sanitation_health/dwq/chemicals/silver.pdf
http://www.watertechonline.com/effects-of-silver-in-water/
http://www.silverhealthinstitute.com/silver-in-drinking-water/
http://www.silver-colloids.com/Pubs/dark-side-rebutal.htm
2. Of interest too was this new water filter I came across called Best Water Technology BWT (website here). They add magnesium to their filtered water, and this seems advantageous as magnesium is important for good health and most people have a deficiency despite it being available through food. From my reading of the various sites (including those above) it even seems that adding in magnesium to your water is still safer and better than silver – I could be wrong though.
If I recall right, you don't advocate stuff being added to drinking water or its nature being changed (e.g. alkaline water). Given all the touted benefits, would you say this for magnesium too?
Some of the links I read on Magnesium:
http://apps.who.int/iris/bitstream/10665/43836/1/9789241563550_eng.pdf
http://www.lifeextension.com/Magazine/2007/2/report_water/Page-01
Yours faithfully
Paloma
Hi Paloma,
It has indeed been a busy time for me, attending to many other commitments outside the topic of water. Sorry to have missed out your questions.
The workshop last Sunday had been a very interesting discussion as I got to meet artists, activists, hobbyists rather than the usual academics, regulators, industrial people and vendor types that I associate with. I will probably post something about it when I have the time.
Silver
This element has been very popular in the past years as part of water filter elements (no pun here)... silver impregnated ceramic candle, silver impregnated activated carbon are the more common ones. The theory is silver has claims to biostatic (stopping microbes from growing) and biocidal (killing microbes) effects. Therefore, it can prevent unwanted microbial growth on your filter elements. Look at it this way, instead of removing bacteria from your water, your filter is now adding them into your treated water.... Yucks!
A few thoughts about silver:
- Elemental silver (the one in your silver coin and jewellery) is pretty insoluble in water so there is no issue of it being toxic this way.
- But what about the silver in my water filter??? In this case, silver is typically applied as silver nitrate (silver nitrate is very soluble!) solution into wet ceramic clay homogenously before the whole mixture is fired in a kiln. This should lock the silver within the ceramic matrix in the finished product. However, various tests have shown that the silver can indeed leach out into water over time. Still, the concentrations of silver in water are very low - ppb (parts per billion) levels or less.
- Back to the biostatic and biocidal claims.... Apparently, these claims are still not well established. Opposing studies have shown that adding silver does not make the filter any cleaner in terms of microbes.
- WHO does not have a guideline value for silver in water as people do not get silver poisoning (argyria) from drinking the normal sources of water though it did mention that the use of silver for its biostatic and biocidal properties may elevate its concentration in water significantly. Hence, WHO did use a nominal value (taken from EPA?) of 0.1ppm (parts per million) that should not be exceeded.
- What about NSF/ANSI certification (1, 2, 3)? One of the requirements for certification of a filter under this scheme requires that it does not leach harmful chemicals into the water. Unfortunately, silver is NOT under the list of chemicals tested since it is of such low priority (in terms of hazard or frequency) as a water contaminant.
- I myself have water filters containing silver for the occasional use out of Singapore. But what if you are using regularly 24/7 for years?
Based on the current literature, silver impregnated filters are probably safe to use. You have to ingest LOTS of soluble silver (say 10g) to suffer from argyria. Though the leaching of silver from a filter may increase over time, you are supposed to regularly change it anyway.
But since you are concerned enough about this issue to write to me and do research, you probably want to be more proactive. Therefore, I suggest that you send samples of treated water to a commercial lab for verification of the silver concentration. Is it less than the nominal value of 0.1ppm? Depending on how often you change your filter, you may want to do this every quarter or half year.
 |
| Figure: My favourite kind of silver |
Magnesium
Magnesium is a vital mineral in our bodies, contributing to controlling heart rhythm, blood pressure, enzymatic activity and others. Its daily requirement is about half that of calcium.
Together with calcium, it also contributes to hard water. No, not the type in which your knuckles get hurt when you try to punch hard water. Instead hard water is well known in industry to cause problems in scaling. It also causes a similar scaling problem when you bath using soap and hard water.
Nevertheless, if you are a fish farmer or aquarium hobbyist, the health of your fishes (and other aquatic organisms) depends on a minimum amount of magnesium.
In recent years, some water ionisers (alkaline water) are selling on the fact that their machines add magnesium
A few thoughts about magnesium:
- WHO does not view it as a health concern! There is no guideline value for it or for hardness.
- Magnesium deficiency in humans in developed countries is not common, certainly not in Singapore.
- A normal diet (nothing extreme) should give an enough supply of magnesium. I am not even talking about supplements. Nuts and milk have it!
- I did not see the amount of magnesium added into water by the water filter in your link. Will you be inadvertently overdosing yourself if your only source of water is from the filter? Since magnesium is connected to many vital functions, it can just as well adversely affect those vital functions. It also has laxative effects!
- Therefore my answer is NO, I don't see a need to have a machine to add magnesium into my water. I certainly do not want to overdose myself either.
 |
| Figure: My preferred sources of magnesium |
No comments:
Post a Comment