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Paul Altmann a Oxford Kidney
Unit, Oxford Radcliffe Hospital, Oxford OX3 7LJ, b The Royal London Hospital,
Whitechapel, London E1 1BB, c Paybody Eye Unit, Coventry and
Warwickshire Hospital, Coventry CV1 4FH, d Priory Hospital, Roehampton,
London SW15 5JJ, e University College London Medical School, London W1N 8AA
Correspondence to: P Altmann
paul.altmann{at}orh.anglox.nhs.uk
Objective:
To establish whether people exposed to
drinking water contaminated with 20 tonnes of aluminium sulphate in the Camelford area of Cornwall in the south west of England in July 1988 had suffered organic brain damage as opposed to psychological trauma only.
Design:
Retrospective study of affected people.
Participants:
55 affected people and 15 siblings
nearest in age to one of the group but who had not been exposed to the contaminated water were studied.
Main outcome measures:
Various clinical and
psychological tests to determine medical condition and anxiety levels
in affected people. Assessment of premorbid IQ (pFSIQ) with the
national adult reading test, a computerised battery of psychomotor
testing, and measurement of the difference in latencies between the
flash and pattern visual evoked potentials in all participants.
Results:
The mean (SE) pFSIQ was above average at
114.4 (1.1). The most sensitive of the psychomotor tests for organic brain disease was the symbol digit coding (SDC) test (normal score 100, abnormal <85). Participants performed less well on this test (54.5 (6.0)) than expected from their pFSIQ (P<0.0001) and a little less
poorly on the averaged less discriminating tests within the battery
(86.1 (2.5), P<0.0001). In a comparison with the 15 sibling pairs
(affected people's age 41.0 (3.3) years v sibling age of 42.7 (3.1) years (P=0.36) the exposed people had similar pFSIQ (114.7 (2.1)) to their siblings (116.3 (2.1), (P=0.59) but performed badly on
the symbol digit coding test (51.8 (16.6)) v (87.5 (4.9) for
siblings, P=0.03). The flash-pattern differences in exposed people were
greater than in 42 unrelated control subjects of similar age (27.33 (1.64) ms v 18.57 (1.47) ms, P=0.0002). The 15 unexposed siblings had significantly better flash-pattern differences than their
affected siblings (13.4 (2.4) ms v 29.6 (2.9) ms, P=0.0002). No effect of anxiety could be shown on these measurements from the
analysis of the anxiety scores of exposed people.
Conclusion:
People who were exposed to the
contaminated water at Camelford suffered considerable damage to
cerebral function, which was not related to anxiety. Follow up studies
would be required to determine the longer term prognosis for affected individuals.
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