Delhi's "poop-from-the-sky" problem is back again, and the NGT wants to know if it is human or bird excreta.
The issue had reached the tribunal last year, when a resident alleged his house was "splattered with large patches of excreta dumped by aircraft".
The NGT had issued guidelines to check the menace.
Though it seems laughable, being hit by poop can have serious consequences.
Delhi's 'poop from the sky' problem
What do planes do with the waste generated on flights?
Planes generally store human waste in special tanks that are emptied once they land.
Sometimes, they add special chemicals to reduce their odor and break it down, converting them to "blue ice".
In January'16, an MP woman was injured after an alleged chunk of blue ice hit her.
In 2015, a UK couple claimed frozen poo from a plane smashed their roof and tiles.
How did the issue reach the green tribunal?
Last year, Vasant Enclave resident Lieutenant General (retd) Satwant Singh Dahiya approached the NGT with a similar complaint, alleging flights were dumping their waste before landing at the Palam Airport.
Once, they reportedly had to spend Rs. 50,000 for "get(ting) the entire exterior resurfaced with fresh paint" after their house was splattered by poop from the sky.
"We...cannot afford to have this defacement everyday."
Love India news?
Stay updated with the latest happenings.
What did the NGT decide?
Taking note of the matter, the NGT in December'16 ruled that "any aircraft (or) airlines" found to be dumping waste before landing would be fined Rs. 50,000 per incident.
It instructed DGCA to conduct surprise checks of aircrafts' waste tanks upon landing to ensure they hadn't been emptied.
In June this year, it rapped the DGCA for non-issuance of a relevant circular.
The waste to be tested before next hearing
Now it has asked a special committee, which includes members from the DGCA, Central Avian Research Institute and Pollution Control Board, to analyze such waste samples from near the Delhi Airport and determine if they are human or bird poop.
Dahiya had even asked for a 24-hour helpline and a monitoring mechanism for the issue.
The next hearing is on December 5.