Is lead in tap water still a public health problem? An observational study in Glasgow

BMJ 1996;313:979-981 (19 October)

Papers

Is lead in tap water still a public health problem? An observational study in Glasgow

Graham C M Watt, professor of general practice,^a Andrew Britton, research and development coordinator,^b W Harper Gilmour, senior lecturer in medical statistics,^a Michael R Moore, reader in medicine,^a Gordon D Murray, director, Robertson centre for biostatistics,^a Stuart J Robertson, operations scientist,^b John Womersley, consultant in public health medicine ^c

^a University of Glasgow, Glasgow G20 7LR, ^b West of Scotland Water Authority, Glasgow G22 6NU, ^c Greater Glasgow Health Board, Glasgow G2 4JT

Correspondence to: Professor Graham C M Watt, Department of General Practice, University of Glasgow, Woodside Health Centre, Glasgow G20 7LR.

Abstract

Objective: To assess the relation between tap water lead andmaternal blood lead concentrations and assess the exposure ofinfants to lead in tap water in a water supply area subjectedto maximal water treatment to reduce plumbosolvency.
Design: Postal questionnaire survey and collection of kettlewater from a representative sample of mothers; blood and furtherwater samples were collected in a random sample of householdsand households with raised water lead concentrations.
Setting: Loch Katrine water supply area, Glasgow.
Subjects: 1812 mothers with a live infant born between October1991 and September 1992. Blood lead concentrations were measuredin 342 mothers.
Main outcome measures: Mean geometric blood lead concentrationsand the prevalence of raised tap water lead concentrations.
Results: 17% of households had water lead concentrations of10 µg/l (48.3 nmol/l) or more in 1993 compared with 49%of households in 1981. Tap water lead remained the main correlateof raised maternal blood lead concentrations and accounted for62% and 76% of cases of maternal blood lead concentrations above5 and 10 µg/dl (0.24 and 0.48 µmol/l) respectively.The geometric mean maternal blood lead concentration was 3.65µg/dl (0.18 µmol/l) in a random sample of mothersand 3.16 µg/dl (0.15 µmol/l) in mothers whose tapwater lead concentrations were consistently below 2 µg/l(9.7 nmol/l). No mother in the study had a blood lead concentrationabove 25 µg/dl (1.21 µmol/l). An estimated 13% ofinfants were exposed via bottle feeds to tap water lead concentrationsexceeding the World Health Organisation's guideline of 10 µg/l(48.3 nmol/l).
Conclusions: Tap water lead and maternal blood lead concentrationsin the Loch Katrine water supply area have fallen substantiallysince the early 1980s. Maternal blood lead concentrations arewell within limits currently considered safe for human health.Tap water lead is still a public health problem in relationto the lead exposure of bottle fed infants.

Key messages

For a given tap water lead concentration mater- nal blood lead concentrations are much lower than they were in 1981
Tap water lead remains the main correlate of raised maternal blood lead concentrations
An estimated 13% of infants are exposed via bottle feeds to tap water lead concentrations of 10 µg/l (48.3 nmol/l) or more
Maternal blood lead concentrations are generally within limits considered safe for human health

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