This is a letter from me, published in the Lancet.
Sir,
Little Arrows
Waldron (The Lancet, December 2nd 1996, page 1975)describes patients who attribute their chronic ill-health to acute exposure to environmental chemicals, although they have no abnormal signs, and biochemistry and haematology are normal. He finds himself unable to support their belief, though unable to refute it - the classic toxicologist's dilemma (1). He suspects somatoform disorder as the underlying problem, and notes that the patients should be protected against unscrupulous physicians and charlatans. With the latter warning we must all agree.
Patients of exactly this type have been presenting to allergists for at least 20 years, attracting some publicity and earning the dubious epithet of "total allergy syndrome" from the popular media. This term irks us immunologists immensely but there is no doubt that the patients exist, that their numbers are increasing, and that their suffering is real. A subset of patients who satisfy the criteria for Chronic Fatigue Syndrome (CFS) also attribute the onset of their illness to an acute chemical exposure, and in this group I agree with Mant (2) that "the illness may be triggered by one factor and promoted by another". This belief of the patients is not ridiculous; there are known biochemical pathways to explain the association, and the normal biochemical and haematological indices merely tell us that we are looking in the wrong place for enlightenment.
Most of us protect ourselves against noxious xenobiotics by using the cytochrome P450 enzyme systems of the liver and other organs, but the P450 system is itself susceptible to damage from carbon monoxide, hydrogen cyanide and other common chemicals(3). Once damaged, it is easy to see how further chemical exposures, at milder dose levels, could keep the system perpetually off balance, leading to a long term sensitivity state in which the original chemical plus many other ambient chemicals would no longer be tolerated. A similar progression is seen in post-teargas asthma, which can remain troublesome years after the initial gassing and in its later stages can be provoked by exertion, cold air, tobacco fumes and car exhausts (4). The beliefs of Waldron's patients are actually quite plausible, but are they correct?
Double-blind challenge is the only way to find out. The patient must be kept in a pollution-free atmosphere for a few days to stabilise, then sat in a gas-proof cabinet into the air-supply of which are introduced, at suitable intervals, likely chemicals at doses likely to be found in ordinary urban air. These challenges are interspersed with "placebo challenges" in random sequence. Pollution-free air (chemically filtered) and challenge facilities are available to NHS purchasers at the Airedale Allergy Centre, Yorkshire. Patients contemplating litigation should be warned that the exercise may be self-defeating, in that a few days' respite from airborne chemicals sometimes allows the enzyme systems to recover, resulting in cure.
Dr David L. J. Freed, MB, MD, MIBiol
References
1) Anonymous.
'Environmental pollution: it kills trees but does it kill people?'
Lancet 1992; 340: 821-2.
2) Mant D.
'Chronic fatigue syndrome'.
Lancet 1994; 344: 834-5.
3) Guengerich FP.
'Analysis and characterisation of enzymes'.
in (ed) Wallace Hayes A.
'Principles and Methods of Toxicology'
1989, Raven Press, New York, 777-814.
4) Hu H, Christiani D.
'Reactive airways dysfunction after exposure to teargas.'
Lancet 1992; 339: 1535.
