Here's an article I would strongly recommend. It's written by Geoffrey Lean in today's Telegraph.
The strap under the headline ("How's your carbon-footprint doing?") reads:
Cutting emissions of carbon dioxide makes sense even if you don’t believe in climate change.
And here is a quotable quote:
"Carbon dioxide emissions are turning the seas acid, and dooming the coral reefs, quite apart from their effect on global warming. Reducing fuel use would also cut other forms of pollution, such as the tiny particles, mainly from car exhausts, that EU research concludes kill some 30,000 Britons each year – shortening average life expectancy by six months – and the nitrogen dioxide which is increasingly implicated in the asthma epidemic that now afflicts one in seven British children...Note regarding that nitrogen dioxide: it's a real insidious nasty. Why? Because the nitrogen does not come from the fuel, unlike, say, the sulphur in that other air pollutant - sulphur dioxide. So there is no point in scientists seeking a low-nitrogen petrol or gas. With the exception of coal, fossil fuels have virtually no nitrogen to start with!
... driving cars less reduces congestion and the building of new roads through the countryside. Walking and cycling are good for your health, as is eating less meat. Using water economically – and thus reducing the vast amounts of energy needed to pipe it around – helps tackle the water shortages threatening areas like the South East. Recycling paper saves trees. And so on."
The nitrogen comes from the air. What happens is this: when our fossil fuels burn inside engine cylinders, gas boilers etc, the high temperature make some of the nitrogen (normally considered chemically inert) to combine with oxygen to make nitric oxide, NO. That colourless gas then combines with more oxygen on cooling to form nitrogen dioxide, NO2. That gas is no doubt responsible for most of the yellowish-brown colour of city smogs, and is highly damaging to our airways and lungs. NO2 is thought to be a major contributor to the increasing incidence of asthma attacks.
Here is a graphic showing the multiple sources of polluting nitrogen oxides in our air.
Source - same Camden link as above.
So wherever you have fossil fuel being burned, you have toxic polluting nitrogen dioxide being formed. Sadly you can't have one without the other - no one's been able to find a way of uncoupling the two.
What a shame that nitrogen dioxide is not soot-coloured instead of being a light yellow-brown. Had it been so, one suspects that our burning of fossil-fuels would be much curtailed - voluntarily!
Afterthought: Some of the pollution by nitrogen dioxide has admittedly been cut by the introduction of catalytic converters, now compulsory in new vehicle exhaust systems. The platinum and other catalysts have been cleverly chosen to make nitrogen dioxide react with another dangerous pollutant - carbon monoxide- to form non-injurious end-products:
It helps, but there's still a hazard from NO2, which is not surprising since it's not just internal combustion engines that create it - see pie chart.