Why is human waste falling from India's skies?

People around the world - most recently in India - report being hit by faeces falling from the sky

In India, as in many other countries around the world, it is considered good luck when a bird poos on you.

But as an unfortunate Indian woman has discovered, there is nothing lucky about being hit by other kinds of falling excrement.

The Times of India reports that Rajrani Gaud from Madhya Pradesh suffered a severe shoulder injury when she was hit by a football-sized chunk of ice last month.

Her injuries could have been much worse, according to eyewitnesses. They say she only avoided being killed because the icy ball crashed into the roof of a house before hitting her.

And the strong suspicion now is that this chilly projectile was composed of more than just frozen water.

The newspaper claims that aviation scientists believe she may well have had the misfortune to become one of an incredibly rare group: people who have been hit by what the airline industry coyly calls "blue ice".

That's its euphemism for the frozen human waste that very occasionally forms around the overflow outlets for aeroplane toilets, and then falls to earth. "Blue" because of the chemicals added to the toilets in planes to reduce odour and break down the waste.

Blue ice falls are unusual, but not unheard of.

Plane toilets store human waste in special tanks. These are normally disposed of by ground crews once the plane has landed, but international aviation authorities acknowledge that lavatory leaks can occur in the air.

Chunks of frozen human waste can "leak" from aeroplanes in mid-air

Britain's Civil Aviation Authority, for example, has said that around 25 falls of "blue ice" are reported every year from the 2.5 million flights a year over UK airspace.

'Party pooper'

Alleged victims of a blue ice fall include a retired couple from Wiltshire in the UK.

Keith and Ruth Mead claim a chunk of frozen poo and urine from a jumbo jet crashed through the roof of their home last year, smashing tiles and leaving a significant hole.

The couple said they were certain of the origins of the object.

"We're sure it came from an airliner passing overhead. Where else would it come from?" Keith told the Daily Mail newspaper.

He says the half-kilo ice ball was yellow and brown in colour and he was anxious about what to put on the insurance claim. "Do we put 'house hit by frozen urine and poo', will they believe us?" he fretted.

Human waste occasionally forms around the overflow outlets for aeroplane toilets before plummeting to the ground

And "blue ice" isn't always frozen, as a 16-year-old in Pennsylvania, USA, discovered in May last year when a very real "party pooper" brought her birthday celebrations an abrupt and messy end.

"Out of nowhere from the sky comes a bunch of faeces," the girl's stepfather, Joe Cambray, told a local television station.

"We'd just gotten done with the cake, thank God," said his sister, Kristie Rogy.

"Because within two minutes something fell from the sky. It was brown. It was everywhere. It got on everything… it was gross".

The family filed a complaint with the American Federal Aviation Authority, but these cases are very hard to prove.

Last year, the New Zealand Herald reported the story of an Auckland man who said his home had been pelted with what he believed was human waste from an aeroplane.

He was furious when the country's Civil Aviation Administration insisted the mess was caused by a passing flock of ducks.