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Sex ratio of the offspring of New Zealand phenoxy herbicide producers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin
  1. Andrea ‘t Mannetje1,
  2. Amanda Eng1,
  3. Chris Walls2,
  4. Evan Dryson2,
  5. Manolis Kogevinas3,
  6. Collin Brooks1,
  7. Dave McLean1,
  8. Soo Cheng1,
  9. Allan H Smith4,
  10. Neil Pearce1,5
  1. 1Centre for Public Health Research, Massey University, Wellington, New Zealand
  2. 2Occupational Medicine Specialists, Auckland, New Zealand
  3. 3Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain
  4. 4School of Public Health, University of California, Berkeley, USA
  5. 5Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK
  1. Correspondence to Dr Andrea ‘t Mannetje, Centre for Public Health Research, Massey University, P.O. Box 756, Wellington 6140, New Zealand; a.mannetje{at}


Objectives Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has inconsistently been associated with a decreased sex ratio of the offspring (number of male births divided by total births). We conducted a study among men and women who were employed in a New Zealand phenoxy herbicide production plant between 1969 and 1984, to study their offspring sex ratio in relation to their back-calculated TCDD serum concentrations determined in 2007/2008.

Methods A total of 127 men and 21 women reported that 355 children were conceived after starting employment at the plant. The association between their lipid-standardised TCDD serum concentrations back-calculated to the time of their offspring's birth and the probability of a male birth was estimated through logistic regression, adjusting for the age of the exposed parent at birth, current body mass index and smoking.

Results The overall sex ratio was 0.55 (197 boys, 158 girls). For fathers with serum TCDD concentrations ≥20 pg/g lipid at time of birth, the sex ratio was 0.47 (OR 0.49; 95% CI 0.30 to 0.79). The probability of a male birth decreased with higher paternal serum TCDD at time of birth (<4; 4–20; 20–100; ≥100 pg/g lipid), with ORs of 1.00 (reference); 1.00 (95% CI 0.50 to 2.02); 0.52 (95% CI 0.29 to 0.92); 0.45 (95% CI 0.23 to 0.89), p trend 0.007. For exposed mothers, the sex ratio was not reduced.

Conclusions This study indicates that paternal serum TCDD concentrations in excess of an estimated 20 pg/g lipid at time of conception are associated with a reduced sex ratio.

  • TCDD
  • sex ratio
  • pesticide production

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  • Funding This study was funded by a New Zealand Health Research Council Project Grant (HRC05/300).

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval Central Regional Ethics Committee CEN/06/02/002.

  • Provenance and peer review Not commissioned; externally peer reviewed.