Disturbance of cerebral function in people exposed to drinking water contaminated with aluminium sulphate: retrospective study of the Camelford water incident

Camelford: prolonging the agony?

8 October 1999

Altmann et al (1) conclude that poisoning with aluminium sulphate in Camelford 10 years ago 'probably led to long term cerebral impairment', an opinion which has predictably led to immediate media attention, including speculation about damage to children and unborn foetuses at the time and doubtless to some rekindling of psychological distress in this population. There is a possibility that the paper by Altmann et al will stimulate a further round of litigation (2). This should be carefully considered because the evidence presented by Altmann et al was obtained under instruction of plaintiffs' solicitors in the context of the earlier round of litigation which ended in 1994, where the out of court settlements were small (average £2,000) and despite the medias assertions, the authors have not presented new evidence.

It is possible that some people exposed to polluted water in Cornwall in July 1988 suffered brain damage (3). However the absence of physiological measures of absorption of aluminium and other toxins at the time of the accident has made it impossible for a definite conclusion to be reached. With regard to persisting complaints attributed to the accident, the paper by Altmann et al is unhelpful and their conclusion unwarranted. Methodological flaws include use of a highly self-selected group of litigants and sibling controls which is a source of bias, however this and difficulties with interpretation of the evoked potential data have been described already (4,5,6).

They also persist in using the unrevised normative data for the National Adult Reading Test, a test which is used to estimate premorbid ability. The revised norms for this test were published in 1991 and are used throughout the UK; by using the outdated version they overestimate IQ in the patient group increasing the likelihood of finding a decrement in tests of current ability.

In addition the authors must be criticised for failing to discuss in depth the relatively few key papers in this area, such as the thorough review by David and Wesseley, or implications from other disasters involving pollution such as Braer (7,8). Perhaps it is because of this that they rebutt possible psychological causation of symptoms oversimply on the basis of 'anxiety' self-reporting and really fail to deal with this complex issue.

Nor do they defend the use of evoked potentials given the crticisms levelled specifically at their work in the second report of the Clayton Committee in 1991 (9).

Finally, they do not acknowledge or explain the absence of effect in the only study on the entire exposed population (of children) who were compared to an age matched non-exposed group of Cornish children on routinely administered psychometric tests of educational attainment given before and after the accident. No evidence for impairment in the exposed group was found-implying that severe brain damage was unlikely to have occurred (10).

In accord with David (5) I think that it is regretable that psychological wounds may be reopened in North Cornwall at such a late stage and seemingly without good reason.However I do hope that plans have been made for early systematic assessment of exposure, and any physical and psychological sequelae in the event of future accidents.

1. Altmann P, Cunningham J, Dhanesha U et al BMJ 1999, 3, 807-811.

2. The Guardian, Friday September 24 1999, p 9 col 1-2.

3. McMillan TM, Freemont AJ, Herxheimer A et al Camelford water Poisoning Accident: serial neuropsychological assessments and further observation on bone aluminium. Human Exptal Toxicol 1993,12, 37-42.

4. Esmonde TFG Methodological errors BMJ letters 1999, 319,7213,807

5. David A Camelford: faulty data and faulty assumptions. BMJ letters,1999, 319,7213,807.

6. Fahy T Competing interests and weak study design undermine conclusions. BMJ letters 1999, 319,7213,807

7. David A, Wessely SC. The legend of Camelford: medical consequences of pollution accident. J Psychosom Res 1995, 39, 1-9.

8. Campbell D, Cox D, Crum J et al. Later effects of the grounding of the tanker Braer on health. BMJ, 309, 773-774.

9. Clayton B Water pollution at Lowermoor North Cornwall. HMSO, London 1991 pp 22-23

10. McMillan TM, Dunn G, Colwill, S.J Psychological testing on children before and after pollution of drinking water in North Cornwall. J. Child, Adolescent Psychiatry, 1993, 34, 1449-1459.

Competing interests: None declared

T M McMillan, rofessor of Clinical Neuropsychology

Department of Psychological Medicine, University of Glasgow

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