An experiment carried out in a Spanish café has shown that the presence of toxic and carcinogenic substances has fallen by 90% since the introduction of a smoking ban there.

While smoking has been banned in all workplaces in Ireland, including pubs, restaurants and cafes, since 2004, a similar ban did not come into effect in Spain until 2011.

In 2010, scientists from the Spanish Institute of Environmental Assessment and Water Research analysed the air quality in a café in Barcelona. After the ban came into effect the following year, the scientists decided to carry out the same analysis.

They found that the presence of harmful compounds - toxic and carcinogenic (cancer-causing) substances - had fallen by 90%.

"The positive impact of the act is substantial in terms of chemical composition, with a 90% reduction in the most critical components when it comes to toxicology," the scientists said.

They also noted that prior to the ban, they detected unusually big concentrations of cerium and lanthanum in the café. These elements comprise the ‘fingerprint' that lighters leave in the air after they have been lit. Prior to the ban, the scientists detected concentrations of these elements that were up to 30 times greater than are found outdoors.

Details of these findings are published in the journal, Particuology.