What is China doing to tackle its air pollution?
"You can definitely smell the pollution. Your eyes itch, you cough. It's like a very rich, dense soup when the pollution levels are very high: thousands of chemicals, gases that are irritants, carcinogens.
"We have particles that have a diameter smaller than a virus. Human hair is very big compared to these. The larger ones will be deposited into the lung - that's the biggest worry. But recent scientific evidence shows that when the particles are small enough they go into the bloodstream, they can go directly into the brain.
"It's very hard to get data to show whether the pollution is going to have a long-lasting effect, like a cancer, but there is a reason to believe that, because the pollution soup contains chemicals which can induce cancer.
"It's very frustrating to see pollution get worse after the huge effort which went into cleaning up the air in Beijing for the Olympics.
"I did several studies demonstrating that if you do a temporary intervention to bring the air pollution down, [and] measure cardiovascular and respiratory health indicators in young healthy people, all those indicators significantly improve.
"Women whose pregnancy was during those eight weeks of improved air quality got babies with a significantly higher birth weight, and we have a large database to show that in general if your birth weight is higher, your later life is healthier.
"In 2008 the air quality data was considered a state secret. The government was in a denial stage for years until 2013 when those huge episodes happened, and then they started to say 'This is real now'. Because of [prioritising] economic interest over public health interest, the way they implement the existing air quality regulations is very inefficient.
"Although it's now getting much better - the urgency is there - it's still very challenging."
"In many situations, industry discharges pollutants without meeting standards. And very often they are not penalised by the enforcement officers.
"The law drafters today are doing a much better job than I did. The environmental laws today are more aggressive: [more] detailed, accurate, and comprehensive than the law I wrote.
"Enforcement is still not good enough. It is slightly better, but it's still far from where it should be."
'Red alerts' represent real progress
"Actually what's happening in China right now is quite positive. [The red alert] is a sign of progress in government's understanding of how they should react and respond to these extreme conditions.
"Not only is it responding to 20 million Beijingers' demand for clean air, it's also setting a precedent for many other Chinese cities to follow.
"After the 'airpocalypse' in 2011/2012, the central government responded with a National Air Pollution Action Plan. At the core of that is a scheme to cut back coal use in the big metropolitan regions.
"Beijing's extreme pollution and the 'red alert' are connected to China's addiction to coal burning, and it's very energy intensive way of industrial growth. Coal burning is the biggest single source of air pollution in China, and burning of coal, has for the first time in this century declined in 2014 compared to 2013.
"That's a very significant thing. As a result air quality in the major cities like Beijing and regions in the Yangtze River Delta has seen improvements.
"Greenpeace has been capturing the government-released hour-by-hour data of 190 cities, and only 15% of them have seen an increase of their readings, and all the rest of them are more or less improved.
"We're seeing renewable energy picking up and taking larger share of total power use in China, and then it's actually already eating up the market space of coal.
"New coal power plants are still being proposed and still being invested [in] by local government and state-owned enterprises as if it was still the good old days. However I doubt there will be enough demand to support them, and they will very likely become idle plants."
