Green environments are being hailed as the cure for asthma.
A study of 50,000 New Zealand children found those who lived in green areas were less likely to develop asthma.
Co-author of the study, professor Jeroen Douwes told Mike Hosking the results were surprising.
"We wouldn't be doing the study if we hadn't expected to find something but I hadn't quite expected the result to come out as strong as it did."
LISTEN ABOVE AS JEROEN DOUWES SPEAKS WITH MIKE HOSKING