Dr Toby Hillman was probably one of the few Londoners happy to be working on Christmas Day last year.
It wasn't because it gave him a chance to get away from turkey and wrapping paper, but because he could cycle through London on one of the quietest days of the year.
"It's a delight," he said. "London's a beautiful place but not when you're living in fear for your life!"
The respiratory consultant works at UCLH and is the Royal College of Physicians' (RCP) healthcare sustainability programme lead. He says cases of asthma and chronic obstructive pulmonary disease (COPD) have increased since he started specialising in respiratory illnesses in 2007.
"Asthma's very typical," he said. "It's not necessarily particulates causing that but the nitrogen dioxide [NO2], which is one of these gases that London exceeds its limits on."
Four out of five COPD cases are caused by smoking, but Dr Hillman says there is now a group of people who have never smoked, or have only been exposed to second-half smoke, getting it too.
Experiments are taking place to pin down exactly why poor air quality plays a role in both conditions, but Dr Hillman said it's caused when the lungs and respiratory system are "ready to react" to something in the atmosphere.
"Breathing in dirty fumes exacerbates that response," he adds.
He now considers exposure to air pollution in every assessment he does. A clear sign air pollution is a contributor to a patient's condition would be that symptoms clear up if they leave the capital and worsen if they come back.
Dr Shumonta Quaderi, respiratory registrar at the Royal Free, said due to the nature of the illnesses, we won't know the effects for decades. She said: "They are long term diseases. You have to be exposed to them for a long period of time, we won't know the impact for 15-20 years."
This week, head of NHS England Simon Stevens declared an air pollution "emergency". A study by King's College London showed it caused hundreds of deaths annually through heart attacks and strokes.
There are clear examples that ambient air pollution affects people from "cradle to grave," according to Dr Hillman. "There's now evidence that particulates, PM2.5s, can move across the placenta," he said. "It can then affect people all the way through life. We're now seeing people who are less responsive to treatment as well because of it. There's no safe level of toxic fumes."
Dr Quaderi adds: "It has a huge impact on your heart and blood vessels, it causes low birth weight, premature births and premature deaths. The problem is respiratory diseases aren't sexy."
It isn't the only health drawback to Brits because of the climate emergency, he says. Changes in the nation's temperatures and rising sea levels will cause more floods. As well as the physical effects, victims of flooding are two to five times more likely to suffer mental health problems.
Extreme heat could cause casualties too. According to an RCP report on sustainability and climate change in the NHS from 2017, there could be 7,000 more deaths a year related to heatwaves and hot temperatures. The 2003 heatwave killed about 2,000 people in England and Wales and the Met Office has previously warned summers like that year could happen every other year up to 2050.
But hope is not lost in the fight against air pollution. "For example, you can stop smoking," he said. "People can save themselves a huge amount and the smoking is obviously unhealthy for you.
"You can have a 'flexitarian' diet which has proven health benefits. It's a reduction in eating meat, especially red meat, which has been linked to bowel cancer and involves intensive farming.
"Active transport is also something else. Walking and cycling. It's better for you and cuts down on carbon emissions."
Dr Hillman himself cycles the 20 miles to work from west London each day. He also says his family is eating less red meat and doesn't fly, preferring "staycations".
Meanwhile Dr Quaderi has adopted another novel way of decreasing her carbon footprint; stopping using a hairdryer. "I have quite long hair," she said. "They give out quite a lot of Carbon Dioxide, so I've stopped using it."
Asked if Dr Hillman finds it frustrating to see a lack of action combined with more patients showing pollution-related symptoms, he says: "Desperately.
"I think it is human nature to put something off until it becomes urgent. You just wish it had been sooner. We need to make this more urgent that people need to be more aware and changing things more quickly. I worry that we don't have the political will to put the interests of society first."
He backs moving away from a car-first approach to city living. He says the new ultra-low emissions zone is a good thing, and supports the phasing out of diesel cars. But he said: "I think it could be more ambitious. The government has not done enough to cut down.
"A way to have a sustainable liveable city would be to design around the needs of people rather than the needs of the cars. When you go to Milton Keynes, it's great for cars and awful for pedestrians. It's not a model of how to live."
"It would be severely limiting the amount of emitting vehicles in London. When Oxford Street is shut down there is a huge improvement in the air quality. People love walking around London when there are no cars."
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