More than 38,000 Ipswich residents are living in areas with air pollution levels above the national target, say a local campaign group.
Based on 2021 census data, just under a third (28%) of the town's population is living in areas of "extremely high" air pollution.
Chris Armstrong and Tony Horner of Ipswich CAN (Clean Air Now) have warned many of these people are living in the air pollution areas without their knowledge.
"Around 38,550 people are living in what are known as Air Quality Management Zones (AQMA)," said Tony.
"These are essentially acknowledgements of the worst areas of air pollution.
"The worst thing is that, in these zones, there are nurseries, junior schools, infant schools.
"It's the very old and the very young that are affected most by air pollution.
"Not a lot of people know they live in an AQMA zone and, if they do, they don't know what it means."
Ipswich Borough Council has declared four AQMA zones across the town.
It is estimated that 65 locals die a year due to air pollution-related illnesses.
"The cause of air pollution is overwhelmingly vehicles", said Tony.
"If you want to reduce air pollution, you need to reduce the number of vehicles.
"Other areas have done some really great work to do this, including implementing things such as zero-emission zones.
"But we're also keen to encourage personal responsibility. For example, try using your car less and, when you do use it, turn your engine off when you stop."
Exposure to high levels of air pollution can lead to a number of health issues, including strokes, heart disease and lung cancer.
Overall, it is believed long-term subjection to man-made air pollution in the UK has an annual effect equivalent to 28,000 - 36,000 deaths.
"We often compare this to smoking," said Chris.
"At one point, you could smoke in public buildings.
"But people were made aware of the health impacts and they began to understand why it was bad.
"That's what needs to happen with air pollution.
"This is a problem everywhere, but Ipswich is one of the worst. We don't want to scare people but they need to be aware of the situation.
"We've got extremely high air pollution and it's affecting our health.
"We now all have to come together as communities to combat it, for the benefit of everyone."
Suffolk County Council's director of public health, Stuart Keeble, and public health consultant, Molly Thomas-Meyer, have been keen to raise awareness of the issue across the county.
"Deaths related to poor air quality are related to particulate matter, effectively dust", said Mr Keeble.
"This can come from things such as cars and industrial processes.
"When we look at the number of deaths, they're not actually people who have poor air quality on their death certificate. They're model figures that say, with the current levels of air pollution, these are the number of deaths it will contribute to.
"It's not good and we need to focus on action."
The pair believe the solution lies in a cross-sector partnership, with a combination of measures implemented by organisations and personal responsibility.
"Part of the issue is raising people's awareness", said Ms Thomas-Meyer.
"We all have roles to play and, if we can understand the different things we can do, we can put together an action plan to map out further changes.
"We wrote the air quality profile last year which makes information locally available.
"Our main aim now is to communicate that, particularly with communities who are going to have increased interest."
Last year, Parliament passed an environmental act which gives the government power to set new targets for air quality.
The act will create at least two new legally binding targets for particulate matter, setting a clear direction for public bodies, private organisations and the public alike.
"The government is prioritising air quality as an issue so it is a national priority," said Mr Keeble.
"We need to take action to reduce the risk for those individuals living in affected areas.
"It is an issue we need to take seriously."
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