Dr David L. J. Freed, MB, MD, MIBiol
"Not since the late 1880's", wrote Metzler in a 1982 editorial in the American Journal of Public Health, "have we been faced with as many unknowns about the quality of drinking water". The State of California had recently been forced to close 39 public water sources because of contamination by chlorinated hydrocarbons. He went on "The knowledge of long-term exposures at low levels has not kept pace with the ability to manufacture new compounds or to detect them; indeed, it cannot be expected to do so by virtue of the time element itself" (1).
Some 90% of the volatile organics in tap water have been identified. 14 of these were selected by the National Cancer Institute for animal carcinogenicity testing; 11 of the 14 were positive in at least one species (1). But the volatiles comprise only 10% of the total water pollution; only 10% of the remaining non-volatiles have been identified, and these include 22 carcinogens, 29 organics for which there are insufficient data on chronic toxicity, and 32 for which there are no data on chronic toxicity (2). Chlorination causes the generation of numerous halogenated organic compounds by reaction with natural humic pollutants, and these are detectable in human serum and urine after ingestion of tap water (3). "The knowledge is just not there," noted Rohlich in 1978, "to enable a safe drinking water to be provided" (2). And the potential toxicity of these pollutant substances in combination have hardly been studied at all. "The magnitude of the research required is so large," noted Thurber in 1970, "that no single individual or agency can adequately conceive or complete the study" (4).
Lest these concerns about man-made water pollutants distract our attention from the hazard of natural pollutants, let us note that waterborne infections are still being reported every year, in spite of filtration and chlorination (2). Nor must we worry only about bacteria. Fungi and algae that sometimes flourish in reservoirs produce numerous excretion products among which are numerous toxins. Tap water in Finland that was thus contaminated caused an outbreak of extrinsic allergic alveolitis in 1980 (5).
Tap water in Manchester contains about 100 mg of solids per litre, as assessed by weighing the freeze-dried residue. When used in skin-testing, this material frequently causes type I (weal-and-flare) or type IV (delayed) reactions in allergy patients. Whilst a positive skin-test does not prove a clinically relevant allergy, it raises a realistic suspicion of one. Aquagenic pruritus is actually quite common, in spite of the tendency of doctors to dismiss the complaint as neurotic (6-8). The classic history is of a patient (usually female) who loves to soak in a scalding hot bath. She gets very hostile when you tell her not to. That, she informs you indignantly, is the only time her chronic itch feels better, the hot water soothes her. The fact that she feels much worse a half-hour later does not impress her. This phenomenon, of feeling better when in contact with the substance that is making you ill, then worse afterwards, is common to all forms of addiction.
80% of commercial underground waters are cytotoxic in tissue culture (9). Water technologists and engineers simply lack the knowledge to make tap water wholesome (10,11). The liquid that emerges from the taps in developed countries is far from being pure H2O. The allergist must always remember water as a potential hazard for ultra-sensitive patients.
I do not know how important this problem is for patients, nor for what proportion, but it is reasonably easy and cheap to clean the water up so it seems logical to advise patients to do so, especially those with positive skin-tests. Bottled spring waters produce fewer complaints, but are certainly not entirely vindicated. In practice I advise a carbon-filter of the jug variety which can be purchased from pharmacists and supermarkets for about £15, and costs pennies to run. For a few extra pence one can also purchase tablets to disinfect water when one suspects bacterial contamination; the disinfectant can then be removed by the carbon filter. Filtration systems that fit into the plumbing for individual taps, showers and even the whole house are readily available for a few hundred pounds, although these are rarely essential. For traveling, patients can either take a portable filter or, in most cases, buy bottled spring water.The main problem with filtered water is that as well as lacking potentially damaging pollutants, it also lacks magnesium, calcium, zinc and other useful trace elements, so a good multi-mineral supplement is useful to make good any shortfall.
References
1)Metzler DF (1982):
'Health implications of organics in groundwater'
American Journal of Public Health 72: 1323-4.
2)Rohlich GA (1978): Drinking water and health.
in (ed) Russell CS;
'Safe Drinking Water: Current and Future Problems'
Resources for the Future Inc., Washington DC, pp 47-75.
3)Reunanen M, Kroneld R (1982):
'Determination of volatile halocarbons
in raw and drinking water, human serum, and urine by electron capture gas chromatography'
J Chromat Sci 20: 449-54.
4)Thurber DL (1970):
Chemical pollution of waters: a modern hydra.
in(ed) Johnson AA,
'Water Pollution in the Greater New York Area'
Gordon & Breach, New York, 75-83.
5)Muittari A, Kuusisto P et al (1980):
'An epidemic of extrinsic allergic alveolitis caused by tap water'
Clinical Allergy 10: 77-90.
6)Anonymous editorial (1981)
'Bath-time itch'
British Medical Journal 282: 1995-6.
7)Greaves MW, Black EK et al (1981)
'Aquagenic pruritus'
ibid, 2008-10.
8)Logan RA, Fehrer MD, Steinman HK (1984):
'The prevalence of water-induced itching.
British Journal of Dermatology 111: 734-6.
9)Coin L, Hannoun C, Trimoreau (1969):
The problem of cytotoxicity of water.
in (ed) Jenkins SH,
'Advances in Water Pollution Research',
Pergamon Press, Oxford, 95-101.
10)Goodman AH (1976):
Potable water is not pure but it must be wholesome -How do we make it so?
in 'Agriculture and Water Quality'
MAFF Technical Bulletin 32, HMSO.
11)King JR, Birch NJ (1989):
'Health hazards on tap'
Lancet i: 1080.
