burning candles and incense in the church can release dangerous levels of potentially carcinogenic particles, warns a recent study conducted by scientists at the Maastricht University in the Netherlands. The team examined the air quality in churches, as these are poorly ventilated with candles burning all day and frequent use of incense.

The researchers measured the particulate matter (pm) concentration in a small chapel and a large basilica in Maastricht after lighting candles for nine hours and simulating a service in which incense was burned. The team found particulate matter less than 10 microns (1 micron equals one thousandth of a millimetre), or pm 10, in the air at levels of 600-1,000 microgrammes per cubic metre