The Daily Mail famously has an ongoing mission to classify all the world's objects into those that cause or prevent cancer. Here's one for the 'cause' list: bottled holy water.
Zam Zam water (also called Zamzam) is beloved of certain Muslims who believe the product, drawn from a well in Mecca, is holy. But the divine refreshment is contaminated with heavy metals, particularly arsenic, and therefore poses a cancer risk. For this reason, it is illegal to import Zam Zam into the UK.
A BBC investigation found the tainted water on sale in bookshops in Wandsworth, Upton Park and Luton. One storekeeper told the BBC that some customers depend on the water, drinking nothing else. The investigation found dangerous levels of arsenic in both the bottled water and taps linked to the source well in Mecca (although no data are presented).
It's not the first time the controversial drink has been splashed across the news pages. In 2007, Westminster Council cracked down on peddlers of fake Zam Zam.
Still, in the interests of balance, here's an account of all the good things the water can do for you, if you favour ancient teachings over biochemistry.