Title: Pesticides and puberty
Key words: immigrants, early puberty, DDT, DDE, oestrogen, malnutrition, breast cancer
Date: May 2001
Category: Life changes
Author: New Scientist
PESTICIDE residues may be affecting the reproductive systems of children in developing countries, say researchers in Belgium.
A team led by Jean-Pierre Bourguignon from the University of Liège has found that children who had immigrated from countries such as India and Colombia are 80 times more likely to start puberty unusually young. The researchers suspect that DDT may be to blame.
Three-quarters of these immigrant children with "precocious puberty" had high levels of a chemical derivative of DDT in their blood. This chemical, called DDE, mimics the effects of the hormone oestrogen, which is important in controlling sexual development.
Children with precocious puberty start sexual development several years earlier than normal. The girls in Bourguignon's study started developing breasts before the age of eight, and started their periods before they were 10.
Youngsters emigrating to other European countries also have an increased tendency to begin puberty early. This effect was thought to be because children who were undernourished in their home countries gain weight rapidly upon reaching the West. But the Belgian researchers found that this theory couldn't explain what they saw. "Some foreign children were not retarded for weight or growth when they arrived," says Bourguignon. And there was no particular home country affected, suggesting genetic factors weren't responsible either.
The team tested the children for a range of pesticides and found that 21 out of 26 immigrant children with precocious puberty had high levels of DDE in their blood. The chemical was only detectable in 2 out of 15 native-born Belgian children.
"The results certainly suggest an environmental factor," says endocrinologist Stuart Milligan of King's College London. But he says more studies are needed to confirm a link with pesticides. "What's dangerous is to create a scare story from something that's not proven," he says.
DDT has been banned in the European Union and the US for decades, but it is still commonly used in many developing countries, mainly to control malaria.
Bourguignon and his team now plan to check whether immigrant children with early puberty have higher levels of pesticide than those who don't. They're also studying the effects of DDE in the lab. Preliminary results suggest that in rats DDE causes the brain to send out the biochemical signals that stimulate puberty. "It may have a priming effect," Bourguignon says.
He suggests that children in developing countries don't normally suffer from early puberty because they tend to be undernourished, and this slows their development down. But even if the effect on puberty is masked, their reproductive systems could still be harmed. "There is concern about other pesticide effects, for example hormone-sensitive cancers such as breast cancer," says Bourguignon.
More at: Human Reproduction (vol 16, p 1020)
© Copyright New Scientist, RBI Limited 2001