Monday, November 15, 2010

Do we really need water filters?

I got an enquiry about water filters and their necessity. I have posted my reply below. (As a side note, I am currently working on a project to determine the effectiveness of water filters in reducing contaminants in our tap water.)



Hi

 I was searching for water filters and happened to see your blog
http://waterqualityinsingapore.blogspot.com/

I had a few queries and hope that you could comment or advise :

 May I know whether the tap water/new water in Singapore is safe to be consumed directly without boiling ?

The tap water in Singapore has its quality benchmarked against World Health Organisation (WHO) drinking water guidelines. Its water quality meets and sometimes even surpasses the requirements given by WHO. From this perspective, yes, tap water in SG can be consumed directly.

As for boiling, it is most effective at killing microorganisms in the water. Boiling can prevent you from getting a case of food poisoning or diarrhea if the water is contaminated by pathogens. However, boiling is not good at removing chemical contaminants such as heavy metals, organic compounds or even chlorine if they are present in the water.


 I heard from salesman selling water filters that tap water contain chlorine which is not suitable to be boiled as it may produce trihalomethanes (THMs) which may cause cancer over long period of usage. 

Yes, our tap water contains chlorine for its ability to prevent the growth of microorganisms in the water. But the concentration is still within the limits given under the WHO guidelines.

Yes, chlorine can form trihalomethanes (THM) under the right conditions. First, you will need organic compounds in the water to react with chlorine to form THM. Usually the organic matter content in our tap water is too insignificant to form any THM. Our tap water is normally slightly acidic (< 7) so THM, if any, will form very slowly as they favour a high (alkaline) pH.

To be fair, the most well known member of THM, chloroform, is (only) a confirmed animal carcinogen with unknown relevance to humans. (Of course, I will rather not take my chances with ingesting chloroform.) The other members of THM are much less studied regarding their toxicity effects.

On the other hand, even disregarding THM, chlorine can be toxic in other ways - by itself or reacting with other chemical compounds IF its concentration in water is high enough. I have heard of water treatment companies in other countries dumping large doses of chlorine to disinfect their tap water and in the process, causing health problems in their consumers e.g. tumours, miscarriages. However, the chlorine in our tap water is definitely much lower (again according to WHO guidelines) as we routinely test it as part of our students' training.


 If that is the case, does it mean that we need to buy water filters in order get rid of the  chlorine before boiling the tap water for making hot beverages ?

Just like issues on food and medicine, water is surrounded by much controversy, especially on the health effects of its components, whether for good or bad. Chlorine in water is no exception. I can't say for certain that chlorine is completely harmless. This is complicated by the fact the health effects are usually only seen in the long term. Performing unbiased studies on human health for the long term (25, 50 years) will be difficult so no one can be sure what the long term effects are.

My thought is if you are worried and you can spare the budget (remember, filters are consummables and require constant changes), do go ahead and get yourself a good filter to reduce the chlorine content in tap water.


 May I know what are the impurities that are still present in the tap water/new water and what are the suitable filter to address them ?

Despite its clear appearance, our tap water contains lots of impurities. (Try googling for "PUB tap water quality".) Water of high purity (Newater by itself is quite pure though) is normally used in microelectronics/wafer fabrication, medical applications, pharmaceutical manufacture. (Actually, high purity water is considered "agressive" and may be bad for health. Oh boy, another can of worms here.)

One impurity of notoriety is fluoride. Our tap water is intentionally fluoridated (addition of fluoride) to fight against tooth decay. However, studies (again inconclusive) have shown that fluoride can be bad for health (arthritis, mutagenicity etc.) and unlike decades ago, we are already getting enough fluoride from our food and toothpaste. Do we still need fluoridation then? Like chlorine, may factors come into play in determining whether fluoride really does exert those negative effects e.g. concentration, time frame. And like chlorine, if you are worried, you should get a filter to reduce fluoride.  (Update: check out Fluoride Action Network for arguments against fluoridation)


I saw "arkwater" filter being mentioned, is it advisable to get it to remove the impurities present like chlorine ?

I believe that the Doulton gravity filter (get the high-end one) from Arkwater is a very good overall filter to remove many contaminants in water - microorganisms, heavy metals, organic compounds, fluoride, chlorine. This is especially critical for disaster or emergency relief when you do not have a clean source of water. Being a gravity filter, it does not need pressure (e.g. water mains) or electricity (what if your power is down). In addition, the filter can handle thousands of gallons of water before needing a replacement. Even if your intention to remove (or reduce) contaminants of unconfirmed health effects as in your case, the filter should still perform beautifully. (I must stress that I am in no way affiliated to Arkwater and derive no benefits from their sales.)


Figure: Doulton (aka British Berkefeld) fluoride removal filter cartridge. You will need this additional cartridge to remove fluoride as the others cannot remove this controversial compound.


Figure: Doulton (aka British Berkefeld) ceramic filter cartridge - the ATC Super Sterasyl model - the highest end for their line of gravity filter cartridges. It contains activated carbon to remove chlorine and organic compounds. Also inside is a metals removal medum.

Figure: Shell of the Doulton filter. The top compartment holds the filter cartridge and accepts raw water. Raw water filters through the cartridge by gravity and you get clean water in the bottom compartment.

At the end of the day, what I am trying to say is beware of sales tactics based on fear only with little or no truth. I am not saying that you should not get a good filter for your domestic use. But if you do, your decision should be based on sound judgement of facts or at least probabilities after weighing the costs and benefits sufficiently.


 Thanks & Regards.

L

4 comments:

CK said...

Hi Mr Kwok, I am thinking of investing in a RO filtration system because I read about concerns that there may be pharmaceuticals and other contaminants leaked into the water supply (e.g. estrogen). Would you have any information on whether there are any tests for contaminants such as estrogen in Singapore's water supply? Thanks.

KCK said...

To give credit to PUB, it does conduct many tests on Singapore's water supply. Some of these tests are beyond the WHO guidelines for drinking water. I am sure estrogen is one of the tests.

kelly chen said...

If PUB does not care for fluoride in water, would they care about estrogen or Teflon residues? I doubt! Do they also test for expired medicine residues, blood contaminants from meat factories? What Big Brother does not discuss publicly, I doubt they provide, KCK.

CK said...

1. Fluoride itself is still a controversial topic with arguments on both sides of the fence.

2. Yes, PUB does not publicise much of their tests and results. I find this area can be vastly improved on i.e. transparency and accountability to the public.

3. However, you ought to find out more, say from their staff (if they are willing to talk to you) before concluding that PUB does not do this or that test.