Although in the past there was concern over the dangers to children of blood lead levels over 25 microg/dL, there is increasing evidence that much lower levels (as low as 5microg/dL have a deleterious effect on child development (see an ALSPAC paper about to be published in Archives of Disease in Childhood).

Further studies are needed to answer the following questions: (a) when in development does the exposure have the most harmful effects? (b) where does the majority of the lead come from? (c) which biological samples are most useful in epidemiological studies of child development?

The programme will use various samples from the ALSPAC survey and develop appropriate measurement methodologies for testing the different sample types. It will compare lead exposure measured in children's teeth over time, distinguishing between levels laid down prenatally, in infancy and later childhood, with maternal whole blood prenatal levels, infant hair and toenails, childhood levels from age 2.5 years, and 7 years. Lead isotope levels will also be measured to assess the likely exposure sources. The aim will be to develop appropriate methods for studies of other population surveys and, when appropriate, for screening the population for appropriate intervention.

In parallel, the epidemiological data concerning maternal prenatal levels of lead, 5000 of which are currently being measured at CDC in Atlanta, will be analysed statistically to determine (i) how closely the prenatal maternal levels correlate with the 2.5 year old measures; (ii) whether the maternal prenatal lead levels are associated with outcomes of pregnancy such as preterm delivery; (iii) whether the relationships with adverse neurocognitive outcomes are predicted with more efficiency using prenatal assays than later measures of child blood.[if so this would be an important time to screen for lead levels].