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

Abstract

Objective: To assess the relation between tap water lead and maternal blood lead concentrations and assess the exposure of infants to lead in tap water in a water supply area subjected to maximal water treatment to reduce plumbosolvency. Design: Postal questionnaire survey and collection of kettle water from a representative sample of mothers; blood and further water samples were collected in a random sample of households and households with raised water lead concentrations. Setting: Loch Katrine water supply area, Glasgow. Subjects: 1812 mothers with a live infant born between October 1991 and September 1992. Blood lead concentrations were measured in 342 mothers. Main outcome measures: Mean geometric blood lead concentrations and the prevalence of raised tap water lead concentrations. Results: 17% of households had water lead concentrations of 10 μg/l (48.3 nmol/l) or more in 1993 compared with 49% of households in 1981. Tap water lead remained the main correlate of raised maternal blood lead concentrations and accounted for 62% and 76% of cases of maternal blood lead concentrations above 5 and 10 μg/dl (0.24 and 0.48 μmol/l) respectively. The geometric mean maternal blood lead concentration was 3.65 μg/dl (0.18 μmol/l) in a random sample of mothers and 3.16 μg/dl (0.15 μmol/l) in mothers whose tap water lead concentrations were consistently below 2 μg/l (9.7 nmol/l). No mother in the study had a blood lead concentration above 25 μg/dl (1.21 μmol/l). An estimated 13% of infants were exposed via bottle feeds to tap water lead concentrations exceeding the World Health Organisation's guideline of 10 μg/l (48.3 nmol/l). Conclusions: Tap water lead and maternal blood lead concentrations in the Loch Katrine water supply area have fallen substantially since the early 1980s. Maternal blood lead concentrations are well within limits currently considered safe for human health. Tap water lead is still a public health problem in relation to the lead exposure of bottle fed infants. 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