While her colleagues were talking tough on climate change in Durban this week, Caroline Spelman, the UK's Environment Minister, faced problems closer to home.

Her department was in the dock on Tuesday over the appalling state of air pollution in the UK.

DEFRA, the UK's environment ministry, was taken to the High Court by international environmental law firm ClientEarth over its failure to meet legal limits on air quality in 17 regions and cities across Britain.

As the ambassador for the UK's Healthy Air Campaign, I was at the Royal Courts of Justice on Tuesday whilst the judgment was being read. The campaign's manager Lewis Merdler commented on the ruling;

"We have fully supported ClientEarth's legal action against the government for failing to deal with dangerous air pollution across the UK. The judge has stated that the government is in breach of EU law and must act urgently or face the consequences. The real losers in this case are the millions of people affected by air pollution across the country, and the thousands who are dying prematurely every year because of inaction to tackle it."

My grandmother still talks vividly about life in central London before the Clean Air Act of 1956. She describes her children's mouths and noses being caked with soot every morning on bad air days, but also the amazing transformation in the air and their health after the act was passed.

Two things spring to mind after listening to her stories;

Firstly how lucky I initially felt that my two-year-old daughter was not growing up in such conditions, but then how naive I was to think that things have changed that much in 2011.

Back then Britain led the way in public health. Overnight the air became cleaner - after a ban on the offending domestic burnt fuel and tighter regulations on industrial use.

But whereas my grandmother could see and smell the smog that prevented her children from enjoying a walk in the fresh air, the type of pollutant that now hovers in our midst is an invisible and slow killer.

Today 29,000 people die prematurely each year in the UK because of the air they breathe. And evidence is now emerging that high levels of air pollution are stunting the growth of lungs in children.

Over 200 local authorities across the UK have declared air pollution hotspots where people are at a significant risk from either or both of these key pollutants: particulate matter (PM10s) and nitrogen dioxide. PM10s are a nasty collective emitted from vehicle exhausts, they comprise of tiny particles of sulphates, carbon, nitrates and other materials.

When inhaled, PM10s and nitrogen dioxide penetrate deep into the lung tissue. The build up continues over many years, but even on days when levels are high we are oblivious to what damage is going on within the inner realms of our body. Unlike high concentrations of surface level ozone that can result in eye irritations, coughing and other breathing ailments, PM10s don't reveal themselves with any immediate adverse signs. However, later on in life, the onset of asthma, emphysema and other bronchial diseases can lead to early death; it's estimated that this means a staggering average loss of 9 years for those that are exposed to the poorest quality of air.

A recent European study (Aphekom) concluded that those living near main roads in cities could account for some 15-30% of all new cases of asthma in children and chronic obstructive pulmonary disease and coronary heart disease of adults aged over 65.

The Healthy Air Campaign's expert on air pollution Ed Dearnley says that it isn't just the young, the sick and the old that suffer from the effects of dirty air. The build up of particulate matter in the lungs takes years, but continual exposure, such as riding a bike to work along busy roads, or exercising in town centres can leave healthy bodies just as vulnerable.

The health impact, work days lost to illness and other social and economic costs of air pollution are similar to obesity or alcohol abuse, but unlike these other two killers the air pollution issue has very little public profile.

With the UK having among the highest frequency of child asthma symptoms worldwide a decisive set of policies to combat air pollution in our towns and cities is essential.

At the very least, we need those in power to recognise the problem and speak up about it. Instead, as Tuesday's High Court hearing showed, we have a government not only failing to comply with European air quality standards, but seemingly willing to accept the likelihood of hefty EU fines as a result.

The former vice president of USA Dan Quayle once said;

"It's not pollution that is harming the environment, it's the impurities in water and air that are responsible."

Whilst David Cameron would never be confused with Dan Quayle in terms of his environmental knowledge, it is time for him to match his awareness of the issues with the leadership we need to tackle this public health crisis.

After all, don't we all have the right to take a stroll down our local high street in the knowledge it won't take years off our lives?

Follow Clare Nasir on Twitter: www.twitter.com/clarenasir