Wales and Northern Ireland have now joined Scotland and the Republic of Ireland in implementing smoking bans in workplaces and enclosed public areas.
A ban came into force in the two countries during April and means only England has yet to follow suit, with its ban due to become a reality on 1 July.
The union body the TUC has urged employers in England not to wait for their ban but to make their premises smoke-free immediately.
It has issued a guide that outlines what employers need to do, such as ensure they have no-smoking signs at all entrances and in any company vehicles, remove all smoking rooms and tackle how to deal with breaks for employees who need to go outside to smoke.
The latest study from Ireland, which banned smoking in March 2004, has reported an 83% reduction in air pollution and an 80% cut in cancer-causing agents in pubs.
The study of 42 pubs and 73 bar workers by the Research Institute for a Tobacco Free Society in Dublin found that workers' lung function had also improved.
But campaigners for smokers' rights responded by saying the level of carcinogens in second-hand smoke was very small.
In a separate development, anti-smoking lobby group ASH has highlighted research from Sweden, published in the journal Tobacco Control, that concluded smokers take almost eight days more sick leave every year than non-smokers.
Across the sample, the average number of days taken as sick leave was 25, but smokers took almost 11 extra days off sick compared with non-smoking colleagues.
Adjusting for other factors such as socioeconomic status and the type of job undertaken, the figure fell to just under eight days on average, said ASH.