1087 It is unfortunate that among Mr Hole’s colleagues are do microscope their patient’s urine ". do so-and use a centrifuged specimen.
before the protective screen commences, so that the resistor attenuates the radio frequency signal to well below one-tenth of its original value. The effect of such resistors on normal 50 Hz patient leakage currents is to produce an infinitesimal improvement, that is, a reduction in leakage. The effect on the displayed E.C.G. signal is undetectable. It does, however, greatly reduce the risk of diathermy burns at E.C.G. electrode sites.
Area Medical Physics Department, General Hospital, Nottingham NG1 6HA.
only a " few who Many more should
Whittier Presbyterian Intercommunity
Hospital, Whittier, California 90602, U.S.A.
CHRONIC LOW-LEVEL LEAD EXPOSURE AND MENTAL RETARDATION D. WHELPTON.
MORTALITY AND WATER SOFTNESS SIR,—The failure of Allwright et al. to find any consistent association between water hardness and deaths from heart-disease, &c., in the Los Angeles area has stimulated correspondence from Dr Meyers (Feb. 15, p. 398) and Dr Anderson and Dr Hewitt (April 12, p. 868). The effect is to leave a cloud of uncertainty over an association which many epidemiologists have hitherto regarded as fairly
strong.2 In view of the recent evidence from animal studies that lead dissolved from water pipes may play some part in increased mortality due to myocardial infarction in softwater areas such as Glasgow,3 it is desirable to point out that very little lead piping is used in the Los Angeles area; it is considered unlikely that soft water was significantly contaminated by lead in the community studied by Allwright etal.l,44 These workers’ results are in fact consistent with the hypothesis that lead dissolved from cisterns and distribution pipes is an xtiological factor in the higher mortality from heart-disease in some soft-water areas. They underline the need for caution in interpreting seemingly negative findings to which Dr Anderson and Dr Hewitt have wisely drawn attention. Department of Chemistry,
University of Reading, Whiteknights, Reading RG6 2AD.
St. Louis Children’s Hospital, 500 South Kingshighway, St. Louis, Missouri 63110, U.S.A.
SiR,—Microscopical examination, as mentioned by Dr (March 1, p. 476) and by Mr Hole (March 15, p. 632), is only a beginning of the examination of the urinary sediment. It would take only a few more seconds for the physician to centrifuge the clean-caught or catheterised urine to learn much more than from a drop of uncentrifuged urine. The physician, using a small centrifuge and a microscope, can carefully run many urines in a short time. In this type of study the physician could be much more certain in telling his patient’s urine is free of infection. (A urine culture is necessary to give the final answer as to whether or not infection exists.) The urological consultant probably sends in a urine culture because the patient had " recurrent infections ". These " recurrent infections " were probably persistent infections that had not been cured because inadequate microscopical examinations were done by the referring physicians. I suggest that all practitioners who treat people with urinary infections examine microscopically, after centrifugation, urine specimens before, during, and after treatment.
SiR,-It is clear that Dr Zarkowsky has not grasped one important points of this work-namely, that we have already established that water-lead levels, measured in the manner adopted by the present study, have a direct cor-
relation with the blood-lead levels and an indirect correlation with the erythrocyte delta-aminolaevulic-acid dehydratase levels of the inhabitants of the household.2 This work was also confirmed by the study of Addis and Moore.33 These studies form the basis of our reasonable assumption that raised water-lead levels relate to increased environmental exposure to lead. We have sent on copies of both papers to Dr Zarkowsky. We have also gone into detail in our paper concerning the further reasons for taking the first-flush samples of water.
The assessed fluid intake, albeit generous, was based intake of 150 ml. per kg., noting that we were considering children up to 1 year of age. A more important consideration, pointed out in the paper, is the increased absorption of lead in infancy as compared to adults both in rats4 and man.5I; Dr Zarkowsky’s statement that the " degree of mental retardation of an i.Q. less than 70 is an unusually severe
Beattie, A. D., Moore, M. R., Goldberg, A., Finlayson, M. J. W. Graham, J. F., Mackie, E. M., Main, J. C., McLaren, D. A., Murdoch, R. M., Stewart, G. F. Lancet, March 15, 1975, p. 589. 2. Beattie, A. D., Moore, M. R., Miller, A. R., Devenay, W. T., Goldberg, A. Br. med. J. 1972, ii, 491. 3. Addis, G., Moore, M. R. Nature, 1974, 252, 120. 4. Kostial, K., Simonovic, I., Pisonic, M. ibid. 1971, 233, 564. 5. Clayton, B. E. Personal communication, 1974. 1.
S. P. A., Coulson, A., Detels, R., Parker, C. E. Lancet, 860. 2. W.H.O. Chron. 1973, 27, 534. 3. Moore, M. R., Goldberg, A., Carr, K., Toner, P., Lawrie, T. D. V. Scott, med. J. 1974, 19, 155. 4. Allwright, S. P. A. Personal communication.
Allwright, 1974, ii,
Robin and others
SiR,-All studies purporting to show a relationship between undue lead exposure and brain insult suffer from being unable to document the blood-lead level, body burden of lead, or lead ingestion during the time that suspected brain damage develops. The report by Beattie et al.1 is no exception. Therefore, in this retrospective survey, how convincing are they in establishing that the retarded children had an increased exposure to lead ? The water-lead level forms the basis for the lead exposure. However, the concentration is of no value in estimating the lead exposure to these children during the first year of life, since no data are given regarding the volume of Do these raised water containing the raised lead level. levels persist in only the first 10, 20, or 100 ml. of tap water, which had resided overnight in the lead pipe ? Furthermore, the authors assume: (1) that young infants drink the gluttonous volume of 2 litres per day; and (2) that formula is prepared from the first-drawn water in the morning without previous flushing. I would have assumed that the first-drawn water was used for preparing breakfast tea. The degree of mental retardation (i.Q. less than 70) is also an unusually severe neurological complication of lead in the absence of documented encephalopathy. It would be of interest to know whether the authors found more than one child from each household with raised water-lead levels.
**We have received the following reply to Dr Zarkowsky’s letter.-ED. L.
URINE MICROSCOPY IN DETECTION OF BACTERIURIA
JOHN A. ARCADI.