The contribution of environmental lead exposure in early childhood to inequalities in child health and cognitive development in the UK Millennium Cohort Study


This project is being carried out by the MRC Centre of Epidemiology for Child Health at University College London and the Small Area Health Statistics Unit at Imperial College in collaboration with the Health Protection Agency and the Centre for Longitudinal Studies. It is expected to be completed in 2013.

Rationale

Lead is a hazardous chemical in the environment and it is increasingly recognised that even low levels of lead exposure can affect children’s learning, development and behaviour. Young children are particularly susceptible because of their hand-to-mouth transfer activities, combined with biological factors such as increased gut absorption and the susceptibility of the developing brain. Although in general sources of lead in the environment have been reduced as a result of a range of government policies, relatively little is known about young children’s exposure to lead at an individual level in the UK partly because in the past this has required blood samples which are not easy to obtain from children. It is now recognised that lead can be measured in milk (first) teeth when they fall out and that different sections of the teeth give information about exposure at different stages of the child's development. We will ask parents to send us shed milk teeth from children taking part in the Millennium Cohort Study at age 7 years when milk teeth have started to fall out in order to answer the following questions:

Research Questions

1.     What is the distribution of lead concentrations in the milk teeth of a population sample of young children in the UK?

2.     How do these concentrations vary by sex, socio-economic position, ethnic group, country, ward type and area of residence, and early feeding patterns?

3.     What is the association of tooth lead concentrations with measures of early childhood motor and intellectual development and health?

4.     How well do current area-based ecological measures of lead exposure predict individual exposure?

Data Collection and Analysis

Parents/carers were invited to take part in the tooth project (called 'every tooth tells a story') by letter, sent in the routine mailing prior to the seven year survey. Those who agreed to take part were asked to post one or more of their child’s shed milk teeth to the ICH.  In the first mailing, 15142 MCS children of 14920 families were contacted and asked to contribute teeth to the study.

To date, a response has been received for 2198 / 15142 (14.5%) children. This is a high response compared with other recent UK studies. One or more teeth have been sent for 2169 of these 2198 children (98.7%).

At the end of the MCS4 CAPI questionnaire, interviewers reminded cohort families about the ‘Every Tooth Tells a Story’ project and there was an opportunity for them to request additional materials.

Preliminary figures suggest that 45% of families indicated that they intended to send one or more teeth back, 19% indicated that they did not wish to participate and 35% requested an additional set of materials. A further mailing of tooth materials was funded which CLS sent to families in May/June 2010.

Responses will be  re-audit after allowing sufficient time for response to this second mailing and will then work with CLS to link tooth response to main data. This will allow biases in response and geographies of response to be assessed as a prelude to finalising analytic strategy (both chemical assay and statistical approach).

Teeth will be analysed for lead content and distribution using appropriate techniques on specified teeth and/or teeth sections and the results linked to relevant variables in MCS in order to address the specified research questions.

Ethics Approval: East London and the City REC 06/Q0603/151

Funding: Health Protection Agency

Contact: Professor Carol Dezateux, Principal Investigator: c.dezateux@ich.ucl.ac.uk