Credit: David Holt, CC BY-SA

The UK government is facing criticism for delaying publication of its air quality plan. The country's high court had ordered the government to urgently revise its strategy for dealing with air pollution, after breaching legally-binding EU limits of toxic pollutants in towns and cities across the Britain.

In November 2016, the court ruled an earlier version of its air quality plan was illegally poor, and it had failed to bring levels of nitrogen dioxide (known as NO₂) down to legal limits in "the shortest possible time". The deadline for a revised version was Monday, April 24.

However on the previous Friday, the Department for the Environment, Energy and Rural Affairs (Defra) filed a last-minute application to delay publication until after the general election on June 8. Defra said the delay was necessary due to "purdah" rules, which limit government announcements during the election period.

The high court has ordered a hearing on the delay. The government is in a strong position to succeed. Even if ClientEarth, the environmental law firm that brought the original case, were to convince a judge that the air quality plan lies outside of purdah, the government could appeal such a judgement. By which time it would likely be beyond the election anyway.

Air pollution is a major issue

The problem is too urgent for such legal holdups. Each year there are around 40,000 deaths due to outdoor air pollution, and the UK has the second highest mortality rate in Europe associated with NO₂ emissions. In busy city centres, the mortality rates are higher.

So what can be done about it? In cities, emissions from road transport are the biggest source of harmful nitrogen oxides (NOx) and fine particles known as particulate matter (PM). To tackle the problem a range of new measures are needed, some of which would be unpopular with many motorists (voters).

Proposals would likely include higher rates of tax for the dirtiest cars and trucks, as well as clean air zones such as the Ultra Low Emissions Zone (ULEZ) in London. The ULEZ, which is due to come into force in 2019, will involve a £12.50 charge (in addition to the current congestion charge of £11.50) for the most polluting passenger vehicles.

Of course, these higher charges will devalue the very diesel vehicles which had been promoted by previous governments. To help, the government has been considering a scrappage scheme (based on a similar scheme in France), where diesel owners would be offered incentives to trade their vehicles for less polluting models.

Diesel vehicles were promoted throughout Europe in the 1990s as they are more efficient than petrol cars in terms of CO 2 emissions, and thus emit fewer greenhouse gases. However, diesel vehicles emit higher levels of nitrogen oxides and particulate matter, the emissions that affect human health.

It's true that diesel vehicles are now much cleaner than they were in 1992, when the first round of European emissions legislation (EURO I) came into force. The regulated level of harmful particulate emissions has reduced by about 97% in that time, with similar trends for NOx.

Diesel engines still emit more NOx than petrol engines, and there are are increasing numbers of diesels on British roads. Car makers have already implemented many of the most obvious and cost-effective measures such as diesel particulate filters. This means that that further reductions of diesel emissions are likely to be more gradual.

This year to date more than 98% of new vehicles registered in the UK still have an internal combustion engine – running on diesel or petrol fuels. While these newer vehicles are less polluting than older models, there are no safe levels for toxic pollutants such as airborne particulate matter.

Fully electric vehicles will take time to catch on, just as the required charging infrastructure will take time to mature. Part of the problem is that drivers are anxious about the range of electric vehicles, which is typically around 100 miles. They needn't be, in London 66% of car journeys are under 5km. Encouraging the uptake of electric vehicles in cities needs a widely available public network of charging points.

But, while the technology and infrastructure is improving, we don't have time to wait for electric cars. The air quality problem needs immediate solutions. To clean up the air the government's plan will need to include higher taxes on the dirtiest of vehicles, and low-emissions zones in most cities.

Explore further London to impose new charges to cut 'lethal' pollution

This article was originally published on The Conversation. Read the original article.