PARIS — Pollution could be behind the rising number of boys born with their testicles in the wrong place, a new study warns. French researchers say babies born with undescended testicles has shot up by as much as 50%, especially in places with coal mines and metal works.
Undescended testicles, also known as cryptorchidism, is the most common male genital defect, affecting between 1% and 8% of newborns. In the U.S., about 200,000 boys are born with the condition each year.
In most cases, the organ corrects itself within six months of birth. Around 1 in 100 boys need surgery to move them into the right position, however. If left untreated, those with the condition may have fertility problems later in life and face a higher risk of testicular cancer.
While certain chemicals have been linked to cryptorchidism, such as phthalates and pesticides, major industrial pollutants have been ignored, until now.
“Our main findings are the increase in the frequency of operated cryptorchidism in France during the study period and the strong tendency for cases to cluster together in particular locations,” says study co-author Dr. Joëlle Le Moal, a medical epidemiologist at the DATA Science Department with Public Health France, in a statement. “This is the first time that such a finding has been documented at a country level for this birth defect.”
The study focuses on 89,382 French boys who went under the knife for cryptorchidism between 2002 and 2014. Results show the number of children with an undescended testicle increased by 36%.
Using a disease mapping model and data on the patients’ home addresses, the researchers identified 24 clusters scattered across France. Most of the clusters were located in the north or central eastern parts of the country. But the largest concentration was around the city of Lens in the Pas de Calais, a former coal mining area.
In Lens, the risk of having one undescended testicle increased by more than 50% compared to national levels. Likewise, cases where both testicles were in the wrong place, known as bilateral cryptorchidism, shot up five-fold, the researchers found.bIn total, 1,244 boys were diagnosed with the condition, 453 cases above the expected number for the area.
“This area includes the two production sites of a former smelter, where most of the local population was previously employed,” says Dr Le Moal. “After more than a century of non-ferrous metal production, it closed in 2003 and induced widespread environmental pollution with metals, especially lead and cadmium. This cluster also includes a metallurgic plant, and two industrial areas still in activity.”
Mining activity was discovered in eight of the 24 clusters, while metal and mechanical works were reported in 17 and 16 respectively. Cases of bilateral cryptorchidism were also higher in agricultural areas with orchards and vineyards, which might be sprayed with pesticides.
“Our results suggest that the geographical environment could contribute to the clustering of cryptorchidism and interact with socio-economic factors,” adds Dr. Le Moal. “The industrial activities identified in the clusters are potentially the source of persistent environmental pollution by metals, dioxins and polychlorinated biphenyls, known as PCBs. PCBs, pesticides and dioxins are suspected to play a role in cryptorchidism and other testicular problems by disrupting hormones.”
Other factors may be responsible for the increasing number of boys being born with undescended testicles in these places, however. Low economic-status, a well known risk factor, could play a part given several of the clusters were in areas where economic activity has declined over the past few years.
Other factors like mothers smoking during pregnancy and premature births could also play a part as they are more common in urban industrialised areas.
“We have highlighted several hypotheses that must be tested in further research,” Dr. LeMoal notes. “Our study is interesting and new because we used a very large, nationwide sample that enabled us to discuss plausible geographical hypotheses. However, these results must not be over-interpreted. The persistent pollutants that we identified could be traces associated with other chemicals. Moreover, we do not know exactly how the population could be contaminated.”
Given the study only included boys who were operated on, it likely underestimates the extent of the health problem.
“This is a landmark study and, in identifying 24 hotspot clusters of cryptorchidism cases scattered across France, it confirms an important role for environmental factors in determining risk of cryptorchidism,” comments Richard Sharpe a professor with Edinburgh University.
The findings are published in the journal Human Reproduction.
SWNS writer Tom Campbell contributed to this report.