Poisoning water as a terrorist measure is not really that easy

We learnt couple of days ago that the water supplies in the UK were threatened with a potential terrorist attack. While I can understand people having concern, I have a bit of a doubt as to whether the threat is that big in the first place. Mainly because of two reasons.

1. The nature of poisons. If you dilute a poison, you reduce its effectiveness, and more dilution the less effective the chemical is. Just like diluting your paint with thinner makes the paint less capable of sticking or drying or longer lasting, diluting your poison means it makes it more and more difficult for the chemical to harm you. This is also another reason why doctors give you doses of medicines. If what you need is 1/2 a gram of medicine per day to fix your ingrowing head hair or twitching ears or whateverthemedicalproblem is, then taking just 10 milli grams wont help.

Water supplies are usually taken from geographic water containers such as lakes or rivers. Given the gigantic amounts of water we are talking about (in the millions of gallons), it is tough to get the relevant amount into the water to really kill people.

Take for example Arsenic, an old and hoary poison used down the ages. To kill a normal sized human being of say 60-70 Kilograms of weight, you need to feed him about 50 grams of arsenic. If you dissolve this into water, the amount of water needed will be much higher. So if you wanted to poison the water in a lake of say 10 million gallons containing to kill all who drink it, you will end up needing not less than thousands of truck loads of arsenic. Sort of will make it difficult to get away cleanly, no?

Even if you go for some of the very highly sophisticated chemical weapons, it is extremely difficult to go over this hump of "dissolving reduces strength".

2. The long processing chain. Even if you did manage to get the stuff in relevant quantities into the water, water companies (usually) have very sophisticated water treatment plants. See here for a good overview of the water purification and filtration process. Generally, the water companies catch any form of impurities much earlier in the process and stomp shut the water supply if they catch any form of impurity, poison, chemicals, etc.

So, no, not that fussed about water born terrorist attacks.


All this to be taken with a grain of piquant salt!!!