Credit: Human Reproduction Environmental pollution from industries such as coal mining and metal works may play a role in the increasing numbers of boys born with undescended testicles, according to a study published today (Wednesday) in Human Reproduction [1]. The researchers stress that their findings are hypothesis-generating, cannot show that these industries cause cryptorchidism and that further, targeted research is required. However, the study of nearly 90,000 boys is the first to describe at a national level a recent increase in incidence of the condition over time and to identify clusters of cases in parts of France that are former mining or metal-working areas, such as the Pas de Calais in northern France. The boys all had operations to correct undescended testicles between 2002 and 2014 when they were younger than seven years.