Choosing the study population
A variety of inclusion and exclusion criteria was applied. For example, children were selected from within a specific age group, all mothers were under 45; all had to have been living in the same area for at least five years, etc. In order to obtain comparable results across the study, recruiters sought a distribution of children across the age range and participants from different socio-economic strata.
Why mother and child pairs?
The EU Environment and Health Action Strategy (SCALE) focuses on children, as they are particularly vulnerable to environmental health factors. Studies of school-aged children also have advantages with respect to ethical concerns, amount of sample material collected and ease of recruitment through schools.
The age group was defined as pre-pubescent, school-aged, 6-11 years. While some recent data have shown onsets of puberty before 11 years, there is no scientific evidence to suggest that early puberty affects the metabolism of the substances being studied.
The selection of this specific age group also enables easy comparison with results from other studies, in particular the US National Health and Nutrition Examination Survey (NHANES), where data for children aged 6-11 are reported separately from other age groups.
Participating children’s mothers were included for a number of reasons:
- To stimulate wider public interest;
- To allow easier access to child volunteers and to increase the acceptability of future child surveys;
- Several participating countries wanted a wider survey to assess the whole population;
- Mothers serve as indicators of foetal and infant exposure, particularly for the youngest children;
- Mothers represent a target group for prevention; and
- Data for mothers living in the same household as the children being studied could lead to insights into exposure sources and pathways.
To guarantee protection of the rights and dignity of every volunteer, all study activities followed the legal and ethical framework established by several international directives, conventions, and guidelines.