By Yvonne Murray in China

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As the UN climate conference draws to a close in Poland, the cities of Northern China are once again shrouded in a dense toxic smog - a familiar sight for Beijing residents.

"The first thing I do when I wake in the morning is check the air," said Deborah Mahon from Dublin who moved to Beijing last year with her family, for her husband's job.

"I have an app on my phone and that gives me the levels. You could walk in less than 200 AQI (air quality index) but you might need to wear a mask. Over 200, we stay in as much as possible," she said.

"You can actually nearly taste the air," she said.

Ms Mahon's house in the northeast of the city has an air purifier in each room. On polluted days, she has to turn them up high.

"They are so noisy," she added, "it does get quite annoying".

As a long-distance runner, the frequent bouts of smog make training difficult.

"I've just finished a race and I feel it's the least ready I've ever been, because you're battling with the air," she said.

"You can't plan your training week. If I take a chance and run on a bad-air-day, the next day I'm very clogged up and headachy. My sinuses flare up," she said.

"At home in Ireland, we would have considered the rain but never the air. And it's quite nice to run in the rain. But I wouldn't run in the pollution - it's not worth it for the health risks," she added.

China's "economic miracle" has brought severe environmental degradation.

The coal and steel-producing regions around Beijing are dotted with heavy industrial sites which constantly belch out toxic fumes.

As the weather gets colder and coal heating systems are fired up, the cities are often blanketed in smog.

Tiny particulates, called PM2.5s, are small enough to enter the lungs and the bloodstream, causing severe health problems.

"Our most recent estimates suggest 1.2 million deaths in 2017 from both household (from cooking and heating with dirty fuels like coal and wood) and outdoor air pollution," said Michael Brauer, Professor at the School of Population and Public Health, The University of British Columbia.

"For outdoor air pollution alone," he added, "we estimate 850,000 from particle pollution and 180,000 from ozone".

The elderly and the very young are at the most risk.

Outside a health clinic in Beijing, parents are buying balloons for their children after their regular check-up.

"I do worry about the effect on my son's health," said a mother called Qing Qing. "He's just over two years old. But living in the city, what can we do?"

"I think Beijing has too many cars," a grandmother said. "But I think the air has got better in the past two years or so."

And air quality has been improving in Beijing, largely as a result of China's government policy.

Air quality index levels have fallen by roughly 33% in the past five years.

The government introduced a "winter action plan" which, last year, saw the closing down of some of the city's more heavily-polluting factories.

At the same time, much of the heating supply was switched from coal to natural gas.

But the sudden implementation of the new policies meant that many homes were cut off from their coal supply before the gas was connected, leaving people to freeze as temperatures plunged.

Schoolchildren in Hebei province were forced to take classes outside as it was warmer in the winter sun than in the unheated classrooms.

China has stated its intention to halt the rise of greenhouse gas emissions by 2030. But it remains heavily dependent on coal.

"Around 63% of power is generated from coal," said Tom Baxter from Belfast who is communications and research officer with China Dialogue in Beijing.

"But that is falling, it was around 70% just few years ago," he said.

"Renewables like wind and solar are making up some of that percentage," he added. "It needs to be fast but it is on the right track."

"You never get used to how much it impacts your life," he added about Beijing's smog.

"You never get over how horrible and depressing it is," he said, "when the AQI is topping 300 and you can barely see 300 metres down the street".

It’s not just China’s problem. Pollution here is partly caused by the consumption of goods and services in other countries.

"In an analysis of data from 2007," said Professor Michael Brauer, "we estimate that goods consumed in western Europe were responsible for 5.4% of the air pollution-related deaths in China."

"That would be 54,400 deaths in China due to consumption in western Europe," he added.

As the US government pursues a climate change-sceptic agenda, China has become the world's largest power calling for environmental protection, despite being the world's biggest carbon polluter.

It is still heavily reliant on fossil fuels and continues to build polluting coal-fired energy plants not only at home but in other countries as part of its Belt and Road infrastructure project.

But simultaneously, China is investing heavily in green energy technology. It is on track, for example, to dominate the world's electric car market.

For now though, as Beijing residents face into another freezing, smoggy winter, change cannot come fast enough.