The smoking ban in Ireland has cut air pollution in pubs and improved bar-workers' health, a study has found.
Air quality has improved in bars since the Irish ban
Researchers said the ban, which came in at the end of March 2004, had led to an 83% reduction in air pollution and an 80% cut in cancer-causing agents.
Workers' lung function also improved, the American Journal of Respiratory and Critical Care Medicine reported.
But smokers' rights campaigners said the level of carcinogens in second-hand smoke was very small.
Smoking bans are already in place in Wales and Scotland. Northern Ireland will follow suit on 30 April, with England's ban coming into force on 1 July.
A team from the Research Institute for a Tobacco Free Society in Dublin, studied environmental tobacco smoke exposure in 42 Dublin pubs and tested 73 bar workers who volunteered to take part in the study.
The workers were all given lung function tests before the ban came in and a year later.
They were also asked about their workplace exposure to tobacco.
The bar-workers said they were exposed to around 40 hours per week before the ban came in, falling to 25 minutes afterwards - a 99% decrease in exposure.
And lung function tests improved dramatically in non-smoking barmen post-ban.
Non-smoking employees also demonstrated significant reductions in cough and phlegm production.
Smokers' health did not improve.
Dr Luke Clancy, who led the research, said: "These results confirm that the approach of a total ban on smoking in the workplace is successful in reducing the exposure of workers to particles."
Martin Dockrell, of Action on Smoking and Health (ASH) said: "Tobacco interests have continued to suggest that there is no evidence that other people's smoke is harmful.
"Dr Clancy's study shows not only how direct the harm is but - most importantly - it shows how comprehensive smoke-free public places can reverse the harm."
But Simon Clark, director of the smokers' lobby group Forest, said self-reporting of exposure and symptoms could not be taken seriously.
He added: "It's hardly rocket science to conclude that smoking bans reduce exposure to airborne carcinogens.
"However, it's the dose that makes the poison and although second-hand smoke may increase people's exposure to carcinogens, the concentration of particles is usually very small.
"A good ventilation system can reduce it even further. "A lot of people may find a smoky environment unpleasant but that doesn't justify a ban on smoking in every pub, club and bar in the country.
"People, including bar workers, should be given a choice of working or socialising in a smoke-free environment or a well-ventilated, designated smoking lounge.
"This feeble report won't change our opinion."