Reproductive health expert John Aitken said researchers had begun investigating whether the male cancer was first triggered by a pregnant woman’s exposure to environmental toxins, such as cigarette smoke.Professor Aitken said the incidence of the cancer had more than doubled in the past three decades and scientists believed environmental pollution was responsible.

He said a woman’s exposure to toxins in the early weeks of pregnancy when the testes were developing may disrupt the normal development of sperm cells.

Scientists suspect the cancer then remains dormant until a boy reaches puberty.

Professor Aitken of the University of Newcastle said Australian scientists were working with colleagues in Europe and the US to identify possible environmental causes.

“There’s some evidence that smoking could be involved,” he said.

“For example, in Denmark which has a high rate of testicular cancer, there’s a very high rate of maternal smoking.”

Researchers also have identified other toxins as possible causes such as nonyl phenols, byproducts of household and industrial waste.

“There’s so much of the stuff flowing down the rivers in the southeast of England, that fish are changing sex,” Professor Aitken said. “And it’s certainly found in the water courses around Australian cities.”

The incidence of testicular cancer in NSW has increased from three in every 100,000 in 1970 to seven per 100,000 last year.

By comparison, cancers of the female reproductive tract – such as ovarian, cervical and endometrial cancers – had either remained the same or declined, Professor Aitken said.

He said the impact of environmental pollution on reproductive health had become a pressing scientific issue.

“Testicular cancer is one of a spectrum of diseases that originate during the development of the baby,” Professor Aitken said.

“What’s very clear is by the time you’re born the die is cast. The more we research into this the more we understand that a healthy pregnancy means a healthy outcome for the individual at the other end.”