Bristol Clean Air Zone could be needed for longer
The law on what constitutes clean air may be set to change
Bristol's Clean Air Zone (CAZ) could remain in place even after pollution levels hit a critical target.
Bristol City Council was forced to implement the scheme to bring levels of nitrogen dioxide down to legal limits, which is expected to happen in about three to four years.
The current legal limit for nitrogen dioxide — a harmful pollutant emitted by petrol and diesel engines — is 40 micrograms per cubic metre of air.
Before the Clean Air Zone was rolled out, 18 sites within the scheme area were above this limit.
Now, over a year later, just six are.
However, that legal limit could soon change.
In 2021 the World Health Organisation slashed its guidelines on how much nitrogen dioxide is safe, from 40 micrograms to just 10.
The issue was discussed by the overview and scrutiny management board on Thursday, January 18.
Green Councillor David Wilcox said: “The World Health Organisation has deemed that the safe level of NO2 is 10 micrograms on an annual basis.
"We’re currently working on the government’s principle of 40 micrograms.
"We’ll have to provide cleaner air for our residents so we will have a Clean Air Zone of some sort to provide clean air.”
Over a year since the Clean Air Zone was launched, the council has evaluated its successes in a detailed report.
In the foreword to that report, Labour mayor Marvin Rees said the scheme “should come to an end” if and when pollution levels fall below legal limits.
Modelling carried out by the council forecasts that all sites within the zone will fall below 40 micrograms within “three to four years”.
However, as evidence mounts of the harm to human health of air pollution, a future government could in theory reduce the legal limit even further.
Green Cllr Tony Dyer, chair of the board, said: “At the moment, the legal obligation we have as a local authority is to meet the clean air standard, which is 40 micrograms per cubic metre.
"That’s a legal standard agreed by the government.
“The standards that have been put out by the World Health Organisation do set a lower standard, but they are not legally binding upon the UK government.
"There may come a time that a future government, of whatever colour, may decide that 40 micrograms per cubic metre is not good enough, and they may say that we have to demonstrate maybe 10 or 25.
“Then we may have to look at whether we need to keep the Clean Air Zone in order to get to those new standards.
"At the moment all the figures are looking like we’re going to meet the current standard within a very short time.
"If there are changes to government legislation then that will be a problem for the next administration, or even the one after that perhaps.”
Once levels of nitrogen dioxide fall below 40 micrograms, that doesn’t mean the council can scrap the Clean Air Zone straight away.
First, three tests will be carried out by government inspectors from the Joint Air Quality Unit.
Inspectors will first check if Bristol has reached compliant levels, and then check again whether air quality has been maintained, and then finally check whether it’s likely to stay below complaint levels.
Only once all three tests have been passed, would the council be allowed to bring the Clean Air Zone to an end.
Separately, the progress made on improving air quality was welcomed by the Asthma and Lung UK charity, but they called for more government support for “cleaner travel options”.
Tim Dexter, the charity’s clean air lead, said: “It’s been encouraging to see the bold action taken in Bristol against toxic air with the implementation of the Clean Air Zone.
"We know these measures work, as demonstrated by the proven air pollution reductions in Bristol.
"A 19 per cent decrease in NO2 levels and a remarkable 27.5 per cent reduction on Park Row reflect the tangible benefits for public health.
“However, this success highlights the pressing need for broader political will by central government, to support other towns and cities with toxic levels of air pollution by providing more support to help people ditch older, more polluting vehicles.
“That’s why we are calling on the government to introduce a targeted support package to help the poorest people in our society, who are the most exposed to air pollution, access affordable cleaner travel options.
"Creating a cleaner, fairer transport system will ultimately improve people’s lives and protect our children from the very real dangers of air pollution.”