Smokers harm their own lungs but might also affect the health of their children and future grandchildren.
Boys exposed to their parents' smoking could grow up to pass on poor lung health to their kids, University of Melbourne researchers have found.
The risk of harm was even greater for grandchildren also exposed to passive smoking.
"Smoking may adversely affect lung function not only in smokers but also in their children and grandchildren," the researchers said.
"Fathers exposed to tobacco smoke during prepuberty may still reduce risk for future generations by avoiding smoking around their children."
Health results from 890 father-child pairs connected to a Tasmanian Longitudinal Health Study were used for the research, published in journal Thorax.
The harmful condition passed on chronic obstructive pulmonary disease, impacts a patient's quality of life and makes it hard for them to breathe.
The World Health Organisation describes it as a "silent killer" and the fourth leading cause of death globally in 2024.
Researchers noted the time before puberty in boys was critical because if they are exposed to harmful substances it can change their gene expression and cells' repair mechanisms, which could be inherited by their children in the future.
The authors cautioned the results were observational and not cause-and-effect.
"This is the first study to investigate and provide evidence for an adverse association of paternal prepubertal passive smoke exposure, rather than just active smoking, on impaired lung function of offspring by middle age," they wrote.
