Hard to swallow: January 2005

Virtue, it has been said, is its own reward. But according to a study by Maastricht University in the Netherlands, which was published in the European Respiratory Journal, religious observance could seriously damage your health.

The atmosphere in churches that is so conducive to prayer and meditation is also, researchers have found, laden with so-called 'indoor pollution' that could pose a threat to respiratory and cardiac health.

Church air was found to be considerably higher in carcinogenic polycyclic hydrocarbons than air beside roads travelled by 45,000 vehicles daily. It also had levels of tiny solid pollutants (PM10s) up to 20 times the European limits.

Fine particulate matter is a major ingredient in air pollution. Consisting of solid particles with a diameter of 10 microns or less, it contains different types of toxic chemicals, including soot, metals and various carcinogenic molecules. The particles can penetrate very deep into the lungs and trigger various lung and heart conditions.

The researchers analysed the particulate matter concentration found in the air of a small chapel and a large basilica in Maastricht following lengthy use of candles or a simulated service in which incense was burned. They found that after nine hours of candle-burning, the church air had PM10 levels of 600 to 1000 micrograms per cubic metre - more than four times higher than before the start of the first morning mass and 12 to 20 times the European allowed average concentration over 24 hours.

The study also uncovered various types of free radicals, including some previously undocumented ones.

The researchers say priests and people working for long periods in churches are at greater risk than the congregation. However, worshippers devout enough to spend several hours each day in church could also be affected.

'Particle pollution, whether it be in an outdoor or indoor environment, can be a danger to lung health and cause respiratory diseases such as emphesyma and bronchitis,' said Dr Richard Russell of the British Thoracic Society.

Barring direct intervention from the Almighty, perhaps the only solution is to hand out face masks at the door and have oxygen at the ready at the end of each pew.