By Martin Shankleman
Employment Correspondent, BBC News
The smoking ban has led to healthier workplaces in the hospitality industry, according to Cancer Research UK.
Smoking was banned in all workplaces on 1 July 2007
In the first report into the impact of the English ban, which was introduced in July, scientists discovered firm evidence of its benefits.
Researchers from Edinburgh and Aberdeen universities analysed the saliva of 39 non-smoking workers before and after the smoking ban came into force.
They found a 75% fall in cotinine, which is a by-product of nicotine.
The level of cotinine is taken as a good indication of how much cigarette smoke has entered the body. Cancer Research welcomed the findings but warned that it would take years before the benefits of the changes would be reflected in mortality rates.
"Although we won't see a reduction in cancer rates for some years to come, the short term health gains we have seen here are very encouraging," said Elspeth Lee from Cancer Research UK.