A new study has shown that the introduction of smoke-free legislation has not led to an increase in children's exposure to secondhand smoke in their own homes.
Before the ban on smoking in public places, many people had voiced concerns that smokers would light up more frequently at home, putting children at an increased risk of the dangers of secondhand smoke.
But a new study in the journal BMC Public Health indicates that this has not been the case.
Researchers at Cardiff University measured the levels of cotinine - a substance formed from the breakdown of nicotine in cigarette smoke - in the saliva of 1,750 Welsh schoolchildren both before and after the ban.
Youngsters were also asked about their exposure to passive smoke.
Analysis revealed that the degree of exposure to secondhand smoke tended to be similar before and after the introduction of smoke-free legislation.
Dr Jo Holliday, from Cardiff University's School of Social Sciences, commented: "Concerns have been expressed regarding the potential displacement of smoking from public places into the home, affecting non-smokers and, in particular, children.
"We found that the smoke-free legislation in Wales did not increase secondhand smoke exposure in homes of children aged ten to 11. Nevertheless, the home did remain the main source of children's exposure."
Despite the reassuring news, Dr Holliday did note that overall levels of passive smoking remain a concern.
The scientist revealed: "Almost 40 per cent of children had a cotinine concentration above 0.17ng/ml - a level associated with lung dysfunction - and almost six per cent of children had salivary cotinine concentrations higher than those of non-smoking Scottish bar workers prior to the introduction of similar legislation in Scotland."
Elspeth Lee, Cancer Research UK's head of tobacco control, said: "The smoking ban has been a huge success. But being at home or in a car remains the main source of secondhand smoke for these children.
"It's important that parents are aware that this could increase their child's risk of leukaemia and breathing diseases like asthma, and are given the support they need to make their homes smokefree and to quit."