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Lifetime exposure to environmental lead and children's intelligence at 11-13 years: the Port Pirie cohort study

BMJ 1996; 312 doi: https://doi.org/10.1136/bmj.312.7046.1569 (Published 22 June 1996) Cite this as: BMJ 1996;312:1569
  1. Shilu Tong, doctoral studenta,
  2. Peter Baghurst, principal research scientista,
  3. Anthony McMichael, professor of epidemiologyb,
  4. Michael Sawyer, directorc,
  5. Jane Mudge, doctoral studenta
  1. a Division of Human Nutrition, Commonwealth Scientific Industrial Research Organisation, Adelaide, SA 5000, Australia
  2. b Department of Epidemiology and Population Sciences, London School of Hygiene and Tropical Medicine, London WC1E 7HT
  3. c Evaluation Unit, Women's and Children's Hospital, Adelaide, SA 5000, Australia
  1. Correspondence to: Dr S Tong, Department of Health Services Management and Public Health, University of New England, Armidale, NSW 2351, Australia.
  • Accepted 3 April 1996

Abstract

Objective: To examine the association between environmental exposure to lead and children's intelligence at age 11-13 years, and to assess the implications of exposure in the first seven years of life for later childhood development.

Design: Prospective cohort study.

Subjects: 375 children born in or around the lead smelting town of Port Pirie, Australia, between 1979 and 1982.

Main outcome measure: Children's intelligence quotient (IQ) measured at 11-13 years of age.

Results: IQ was inversely associated with both antenatal and postnatal blood lead concentrations. Verbal, performance, and full scale IQ were inversely related to blood lead concentration with no apparent threshold. Multivariate analyses indicated that after adjustment for a wide range of confounders, the postnatal blood lead concentrations (particularly within the age range 15 months to 7 years) exhibited inverse associations with IQ. Strong associations with IQ were observed for lifetime average blood lead concentrations at various ages. The expected mean full scale IQ declined by 3.0 points (95% confidence interval 0.07 to 5.93) for an increase in lifetime average blood lead concentration from 0.48 to 0.96 µmol/l (10 to 20 µg/dl).

Conclusions: Exposure to environmental lead during the first seven years of life is associated with cognitive deficits that seem to persist into later childhood.

Key messages

  • Few longitudinal data have yet been reported on the time course of the effects of exposure to environmental lead

  • Exposure to environmental lead early in life is associated with cognitive deficits that persist into middle childhood

  • The duration, intensity, and timing of exposure to lead, as well as other social and familial factors, may influence the nature and degree of reversibility

  • The formulation of a public health policy for preventing any possible effects of lead exposure should be based on a composite consideration of the child's health and the best use of existing resources

Footnotes

  • Funding This research was supported by a series of grants from the National Health and Medical Research Council, the Channel 7 Children's Research Foundation, and the University of Adelaide.

  • Conflict of interest None.

  • Accepted 3 April 1996
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