Churchgoers risk lung cancer because of unhealthy air caused by candles and incense, researchers say.
The scientists found new forms of “free radicals” that could threaten Roman Catholic rituals.
Most at risk would be priests and those who work in churches but “worshippers devout enough to spend several hours each day in church could also be affected”, the scientists say.
After nine hours of candle burning, the normal daily amount, the atmosphere in the Roman Catholic basilica in Maastricht, Holland, had readings between 12 and 20 times higher than European clean air guidelines.
The air quality was worse than in an area used by 45,000 vehicles a day.
The measurements were taken in a small chapel and large basilica of the Onze Lieve Vrouwe Basilek through the day, and before and after simulated services.
Dr Theo de Kok and colleagues from the department of health risk analysis and toxicology at Maastricht University said they were “stupified” by the readings.
“While we still have to assess precisely what level of risk these people are running and how toxic the newly identified free radicals are, the discovery is very worrying,” Dr de Kok said.
Fine particulate matter (PM) is a key ingredient of air pollution and consists of solid particles with a diameter of 10 microns or less. PM10 levels are a standard way to measure air quality.
After nine hours the church had PM10 levels that were 600 to 1,000 microgrammes per cubic metre, four times higher than those measured before the first morning mass.
“This is 12 to 20 times higher than the European allowed average concentration over 24 hours,” says Dr de Kok in December’s European Respiratory Journal, out next week. The EU standard is 50 microgrammes per cubic metre.
He found high levels of aromatic hydrocarbons, which are well known carcinogens, and the free radicals “including undocumented ones”.