Last checked at 
* Delhi's air quality levels on Nov 1. worst in 2019 -data
* Air quality stays severe for third straight day
* Delhi government orders schools to be shut until Nov. 5
* City govt plans to distribute 5 million masks in a week
(Recasts with data, context, quotes)
By Neha Dasgupta
NEW DELHI, Nov 1 (Reuters) - Authorities in New Delhi
declared a public health emergency on Friday and closed schools
and all construction activity until next week as air pollution
in the city hit its worst level this year.
A thick haze has hung over the Indian capital this week
caused by plumes of toxic smoke from farm fires raging in
neighbouring states.
An index measuring the level of a deadly air pollutant hit
484 on a scale of 500 on Friday, the government's Central
Pollution Control Board, the worst this year.
The index measures the level of PM 2.5, tiny particulate
matter that goes deep into the lungs. Anything above 400 poses
a risk for people with respiratory illnesses and can also affect
even those with healthy lungs.
Some companies advised employees to avoid exposure to toxic
air and work from home.
"We have been advised to stay at home on Monday," said Anuj
Rawat, an account director at Kantar, the market research arm of
British advertising major WPP. Kantar employs around 400
people at its office in New Delhi, Rawat said.
The Environment Pollution Control Authority, which is
leading the effort to tackle Delhi's pollution, said: "We have
to take this as a public health emergency as air pollution is
now hazardous and will have adverse health impacts on all, but
particularly our children."
It banned all construction work in the sprawling metropolis
of 20 million people and its neighbouring cities until Nov. 5.
Each year, farmers in the states of Punjab and Haryana burn
crop residue to prepare for the sowing season, ignoring
government warnings.
According to government-run monitor SAFAR, satellite
pictures had captured nearly 3,200 incidents of stubble burning
on Thursday in Haryana and Punjab that contributed to 44%
percent of Delhi's pollution.
Delhi Chief Minister Arvind Kejriwal offered free masks on
Friday and ordered schools shut till Nov. 5 to protect children.
The toxic air has left several Bangladeshi cricket players
with sore throats and itchy eyes ahead of their Twenty20 match
against India on Sunday.
"Government knew an emergency situation was approaching and
did not take substantive steps on stubble burning or big
industrial polluting sources," said Sunil Dahiya, an energy and
air pollution analyst at Greenpeace.
"A public health emergency situation began at least 10 days
ago."
(Reporting by Neha Dasgupta
Additional reporting by Anuja Jaiman
Editing by Kim Coghill, Sanjeev Miglani and Frances Kerry)
