Delhi draws three-quarters of its drinking water from the Yamuna river, into which the city dumps quantities of sewage, almost all of it untreated, to join a cocktail of farm chemicals and industrial effluents, including arsenic.

ECONOMIST: Bursting cities, bust infrastructure

The FSA says it tested almost 80, 000 samples of food last year and focuses "on those risks that can make people ill or worse" including looking for arsenic and listeria.

BBC: Horsemeat scandal: FSA inquiry 'will be relentless'

He said second-hand smoke contained more than 4, 000 chemicals, including benzene, formaldehyde, arsenic, ammonia and hydrogen cyanide.

BBC: NEWS | UK | Northern Ireland | Legal threat over passive smoking