The researchers found that larger amounts of both CB-153 and DDE in the blood of the fishermen was associated with a statistically significant increase in the proportion of Y chromosome bearing sperm in semen, and that age, smoking and hormone levels had no effect.
"When we compared the 20% of fishermen with the highest exposure with the 20% with the lowest exposure, DDE was associated with an increase of 1.6% in sperm with Y chromosomes and CB-153 with an increase of 0.8%. To our knowledge this is the first study to show that the distribution of the sex chromosomes in sperm can be affected by exposure to POPs," said Prof Giwercman.
The study did not enable them to discover whether the increase in Y chromosome sperm would lead to an increase in boys being born, or what might be the mechanism involved. "We need a much larger population in order to investigate the implications of these changes on sex ratio of offspring as the number of children born to these fishermen was small.
"However, we think the fact that exposure to environmentally derived chemicals can change the sex chromosome ratio in sperm is worrying in itself and requires more attention from scientists and the public," said Prof Giwercman.
The second study by researchers from Denmark, Lithuania and Finland suggests that a higher than expected prevalence of cryptorchidism (undescended testes) in Lithuania could be occurring because changing environmental factors are affecting the reproductive development of male foetuses.
Babies born with undescended testes are at higher risk of developing testicular cancer between the ages of about 20 and 40, and of having infertility problems. Cryptorchidism is one of the symptoms of testicular dysgenesis syndrome (TDS) ?a collection of male reproductive disorders, possibly caused by errors in development of the foetal testes.
The Lithuanian study investigated
Source:European Society for Human Reproduction and Embryology