Ipswich campaigners say they are "gobsmacked" after the government admitted air quality targets set by experts and the EU would not be possible.
Environment secretary Thérèse Coffey has set clean air targets lower for the next 10 years - despite researchers saying the initial goal was reachable with stronger action.
38,000 Ipswich residents are living within 500m of areas with air pollution levels above the national target, with government modelling estimating 65 residents die from related illnesses every year.
Dr Coffey said on Tuesday: "I would have loved to have made our target to achieve 10 micrograms [of fine particulate matter], by 2030, not 2040.
"But the evidence shows us that with the best will in the world we cannot achieve that everywhere by the end of the decade."
Tony Horner, of Ipswich CAN (Clean Air Now), said he was "gobsmacked" by the news.
"It's so frustrating," he added.
"The government keeps telling us about the health impacts of air pollution, but isn't doing enough to tackle it.
"They won't be in power in 2040, so they're just abdicating responsibility."
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