Children are more likely to develop asthma if their father was exposed to second-hand smoke when he was a child, according to a new study.
The research, published in the European Respiratory Journal, also shows that children's risk of asthma is even higher if their father was exposed to second-hand smoke and went on to become a smoker.
These findings highlight how smoking can damage health not only for smokers and their children, but also their grandchildren.
Health study
The research was led by Mr Jiacheng Liu and Dr Dinh Bui from the University of Melbourne, Australia.
It was based on data from the Tasmanian Longitudinal Health Study (TAHS), led by Professor Shyamali Dharmage.
TAHS began in 1968 and is one of the world's largest and longest ongoing respiratory studies.
For this study, researchers looked at 1,689 children who grew up in Tasmania, their fathers and their paternal grandparents.
Increased risk
They compared data on whether the children had developed asthma by the age of seven with data on whether the fathers grew up with parents who smoked when they were under the age of 15.
They also included data on whether the fathers were current or former smokers.
Mr Liu said: "We found that the risk of non-allergic asthma in children increases by 59% if their fathers were exposed to second-hand smoke in childhood, compared to children whose fathers were not exposed.
"The risk was even higher, at 72%, if the fathers were exposed to second-hand smoke and went on to smoke themselves."