Sparkling, fresh… tap water.

I decided to look into water purity, as I’ve heard a lot in recent months from both “camps” - those who think that bottled water is better and those who cling to tap water. 

First off, the links, if you want to know where I looked:

UK tap water requirements (skip down to “Schedule 1")

Bottled/mineral/spring water requirements

The following “ingredients” had the same allowable maximum concentration across the board:
- antimony (5 micrograms/L)
- arsenic (10 micrograms/L)
- boron (1,000 micrograms/L)
- chromium (50 micrograms/L)
- mercury (1 microgram/L)
- nickel (20 micrograms/L)
- nitrate (50,000 micrograms/L)
- selenium (10 micrograms/L)

As far as pesticides went, the requirements were all the same: no more than0.5 micrograms/L.  Similarly, the requirements for polycyclic aromatic hydrocarbons, tetrachloroethene and trichloroethene, vinyl chloride, acrylamide and benzene were the same across the board. 

As for the ones which had different requirements (blue-highlights indicate the lower allowable concentrations):

* couldn’t find any restrictions
¹ after 2013, allowable amount will be lowered to 10 micrograms/L

Conclusions

The bottom line, really, is that I personally don’t see much difference between the choices.  The government would certainly set maximum allowable limits much lower than those required for toxicity, although I have to admit, knowing that lead builds up in the body, that I would prefer there to be less of it floating around in my water.  However, I’m still going to quite happily drink the tap water, since it seems likely to me that all the nasties produced when making the plastic to bottle “natural mineral” water in probably far outweigh any slight cleanliness advantage that bottled water might have over tap water.

If you’re interested, I’ve put brief descriptions (courtesy Wikipedia, that fount of occasionally-faulty facts) of the differing-concentration “ingredients” below.  I meant to put them in the “more” section, but I’ve been switched by my webmaster into a new blog-editing setup and can’t figure out how to make it separate the “more” section out.  Please keep in mind that I haven’t had any form of biology or chemistry since the late 1990s, and therefore am probably not getting the finer points.

(On an amusing side-note, the (i) note to Schedule 2 of the Water Supply (Water Quality) Regulations 2000 states that “The water should not be aggressive.” Glad to hear it.)

Barium: “At low doses, barium acts as a muscle stimulant, while higher doses affect the nervous system, causing cardiac irregularities, tremors, weakness, anxiety, dyspnea and paralysis. This may be due to its ability to block potassium ion channels which are critical to the proper function of the nervous system.” However, barium doesn’t bioaccumulate, and also (confusingly) is highly reactive to water, producing hydrogen.

Cadmium: “Inhalation of cadmium-containing fumes can result initially in metal fume fever but may progress to chemical pneumonitis, pulmonary edema, and death…Human exposures to environmental cadmium are primarily the result of the burning of fossil fuels and municipal wastes… Cadmium is one of six substances banned by the European Union’s Restriction on Hazardous Substances (RoHS) directive, which bans carcinogens in computers.  Cadmium and several cadmium-containing compounds are known carcinogens and can induce many types of cancer… Tobacco smoking is the most important single source of cadmium exposure in the general population. It has been estimated that about 10% of the cadmium content of a cigarette is inhaled through smoking. The absorption of cadmium from the lungs is much more effective than that from the gut, and as much as 50% of the cadmium inhaled via cigarette smoke may be absorbed.”

Copper: an essential trace nutrient which contributes to the production of blood cells and helps out with various other enzyme functions.  In toxic amounts, copper inhibits blood cell production, and fatal cases are generally terminated by convulsions, palsy, and insensibility.”

Cyanide: Can be used medically, to reduce blood pressure rapidly (in emergency situations). Used in mining to easily separate precious metal ore from slag (a process that generally releases large quantities of cyanide and other interesting chemicals into the local environment, particularly the water course.) Used illegally to capture live fish near coral reefs (acts as a stunner).  When toxic, cyanide inhibits the aerobic production of ATP within the body, particularly affecting the central nervous system and the heart.

Fluoride: In low concentrations, helps teeth enamel become more resistant to decay.  In high concentrations, fluoride compounds cause death, although I couldn’t find out how they do so, only that it has something to do with absorption through the intestine.  Long-term ingestion of [contested] quantities of fluoride can cause yellowing of the teeth, and some people think that it also contributes to bone weakness and brain damage.

Lead: Basically, lead causes brain damage, blood disorders, reproductive disorders and mental disorders.  It inhibits hemoprotein production, which buggers anything having to do with, as far as I can tell, anything.  (My chemistry/biology background isn’t enough to get me through the wikipedia page about heme.)

Manganese: plays a crucial role in a number of enzyme functions, which is why it’s considered an essential trace nutrient. In toxic levels, it can impair motor skills and contribute to cognitive disorders.

Nitrite: “Under certain conditions, especially during cooking, nitrites in meat can react with degradation products of amino acids, forming nitrosamines, which are known carcinogens…”