On the same day, mother and child collected their morning urine. The recipients were stored in the refrigerator. At the school's request, the child was weighted and measured. A small lock of hair was then collected and the field worker, along with the child, filled in a short questionnaire relating to hair. An appointment was then made with the mother to also measure her height and weight and collect some hair. The field worker questioned her for about 45 minutes regarding her eating habits, lifestyle, living environment, occupation, hobbies and the use of care products.