Pilot study   Cohort 1 Cohort 2 Intervention study Cohort 3  Cohort 4 Main references Grandjean et al., 1992 Grandjean et al., 1992 Steuerwald et al., 2000; Grandjean et al., 2001 Weihe 2001 (unpublished data) See section 6.2 See section 6.3 Period of establish- ing the cohort December 1985     1.3.1986 – 31.12.1987 3/1994 – 4/1995 2/1999 (first hair samples and questionnair e) 3/2000 (second hair sample) 12/1997 - 2/2000 10/2000- 10/2001 Mode of selection All women in the fertile age group (20 to 50 years old), residing in the small fishing village of Leirvík in the Faroe Islands Consecutive births at all three hospitals in the Faroe Islands Consecutiv e singleton births of mothers residing outside of the Tórshavn area at the hospital in Tórshavn   Questionnair e about diet and twice a request for a hair samples were sent to all women residing in the Faroe Islands, aged 26 to 30 Consec utive births at the Nationa l Hospita l in Tórshav n, all mothers include d Consecuti ve births at all 3 hospitals Number of participants 53 1,022 182 370 (one hair sample) 146 (two hair samples) 539 (questionnair e) 656 148 Portion of all eligible children born in the period (84% out of the 63 women of this age group) 75% 64% 31.4%  (one hair sample) 12.0%  (two hair samples) 45.7%   (questionnair e) 55.3% 49.7% Maternal age: mean (SD) N.a. 26.9 years   (range 15– 45) 28.0 years (± 5.8) N.a. 29.2 years (± 5.2) (range 16– 43)   29 17-40) BMI (kg/m²) mean (range) N.a. 22.3 (16.0 – 42.4) 23.1 (17.0 – 38.6) N.a. 23.9 (16.6 – 44.1) 23.7 Number of teetotaller mothers N.a. 771 (75.4%) 159 (87.4%)  N.a. 375 (58.6%) 49.7% (in 2. trim.) Number of non- smokers N.a. 614 (60.0%) 125 (68.7%)  N.a. 448 (70.0%) 122 (74%) N.a. = Not available