Farmers can breathe easy after scientists discovered that working with manure can drastically reduce chances of developing lung cancer.

New Scientist magazine reported dairy farmers were five times less likely than the general population to develop the disease.

It found farmers typically breathed in dust that consisted largely of dried manure, and all the bacteria that grew in it.

“As strange as it sounds, epidemiologists are starting to uncover unexpected links between our exposure to dirt and germs, and our risk of cancer later in life.”

New Scientist said adults who had a greater exposure to germs than usual might build up a better resistance to bugs, including cancer.

“Some researchers are starting to wonder whether the higher incidence of certain cancers in affluent populations – including breast cancer, lymphoma and melanoma – might also have something to do with sanitised, infection-free living,” it said.

“If they’re right, the implications are huge. If we can understand exactly what it is about some germs that has a protective effect, we should be able to reduce people’s risk of developing certain tumours later in life by exposing them to harmless microbes.”

But Mike Berridge of the Malaghan Institute of Medical Research in Wellington said the report might not be very relevant to farmers here.

“I’ve been aware of some studies on asthma and farm workers but this one is a bit out of the blue. I’d be very surprised if it is the case,” he told The New Zealand Herald newspaper.

“It’s very different overseas because they keep animals in barns and out of the weather and they don’t have outdoor farming. I suspect something like that would be more relevant to European farm workers than New Zealand farm workers.”