The impact of chemical pollution on male reproductive health
We are encouraged to eat more fruit and vegetables as part of a healthy lifestyle but this advice could in fact be damaging our health. With ever more commercial food production, research shows that traces of pesticides used on crops can make their way into our food system and into our bodies where they can disrupt hormone function.
Pesticides are just one of the chemicals we are exposed to from the environment; by-products of industry, plastics and synthetics we use daily, such as cosmetics and air fresheners, all make their way into our systems. There is already a European framework that studies the risk of certain chemicals to human health but their impact is assessed one at a time.
As European citizens are regularly exposed to multiple chemicals with a hormonal effect, the CONTAMED project began in 2008 to look at mixture effects - how various chemicals work together to produce joint effects. The three-year study, which finished in November 2012, has examined these cumulative effects in vitro and in the lab.
The chemicals under the microscope at the eight institutions across six EU countries were chosen as they were already known to disrupt the endocrine system – the cells that detect and react to hormones in the body. One area of human health that this especially affects is reproductive health and foetal development. Hormones called androgens, such as testosterone, control the development of male characteristics; if they don’t play their part then boys will show signs of demasculinisation through malformations and illness.
Hormonal malformations can include non-descending testes and hypospadias, a condition where the urethra opens on the underside of the penis rather than at the tip. Undescended testes affect around 3-5% of boys born in Europe. By working backwards, scientists involved in the CONTAMED project analysed whether the mothers of these boys have higher levels of certain chemicals in their body fluids.
“If the action of the male sex hormones doesn’t kick in foetal life the default trajectory of development is female so you have cases where people look like a woman but genetically are a male. This is a very extreme example of how important the sex hormone is to program boys,” said Professor Andreas Kortenkamp, project leader for CONTAMED.
In three European bases – in Granada, Rotterdam and Bristol – researchers analysed tissue specimens from mother-son cohorts with cutting-edge analytical techniques to see if there is a link between exposure to chemicals and adverse reproductive effects. The results were due to be published at the end of 2012.
In parallel to the human studies, the researchers tested the chemicals under experimental conditions. By recreating the combinations of chemicals that humans are routinely exposed to and testing their effect on rats, they hoped to give a reassuring message to the public.
“No-one has ever done this; we were quite ambitious and quite amazed how well it worked,” said Kortenkamp. “We combined these chemicals at approximately 100 times the human level and gave it to rats, hoping not to see any effects. But we did.”
Rats are able to process chemicals much faster than humans so in toxicological assessments the rats are given a higher dosage to attain tissue concentrations similar to humans. If at this exaggerated concentration there is no effect on the rats then an exposure 100 times weaker is assumed tolerable for humans.
The effects that the chemicals had on the rats, stunting male development and resulting in their demasculinisation, were published in the International Journal of Andrology. They show that our health could be at risk from these chemical cocktails. “This highlights how important it is in toxicological risk assessments to look at mixtures, which is still not routinely done,” explained Kortenkamp.
Project acronym: CONTAMED
Participants: United Kingdom (Coordinator), Netherlands, Spain, Denmark, Switzerland, Germany