Residents on a road which has some of the UK'S highest pollution levels say they fear for the health of children.
In 2015 and 2016, recorded levels of nitrogen dioxide on the A472 at Hafodyrynys were higher than anywhere else apart from central London, according to government figures.
The level far exceeds World Health Organisation guidelines on acceptable levels.
Caerphilly council said it was looking at ways of improving the situation.
The Department for Environment, Food and Rural Affairs (Defra) has monitoring boxes placed at locations around the UK, which monitor air pollution levels.
A box on the A472 is near Swffryd in an area where a high number of lorries travel between Crumlin and Pontypool, while motorists coming from the M4 and Heads of the Valleys also use it.
"I'm concerned about pollution on the children. Once you breathe it in day after day, it has got to make a difference especially on young lungs," said Merilyn Lewis.
"It is like living in the middle of the road."
Councillor Andrew Lewis said exhaust fumes came from lorries revving their engines to get up the hill and cars queuing during rush hour.
He has started a campaign against a proposed new access road from Tirpentwys down on to the A472, also known as Hafodyrynys Road, saying it is already too congested.
He said: "You won't see a window open because of the cars and fumes drifting, nobody daren't."
Local resident Steve Trigg, 57 said he had got used to any pollution.
John Scofield said his car got dirty with dust, while Mary Hadigate said the speed of cars on the road meant she feared crossing it.
"The road wasn't designed for lorries," said Alan Heaps, referring to one revving its engine to get up the hill.
"You only have to look at the door colours, you have to wash them weekly. If you don't they get rotten. The walls are also black."
A Caerphilly council spokesman said it was aware of the high readings returned.
"The area has been designated as an air quality management area and the council is working alongside key stakeholders to look at options to improve the air quality in the area," he added.
A Welsh government spokesman said it worked with Defra and the European Commission to improve air quality.
He added that local authorities had a duty to review and assess air quality and where desired levels were unlikely to be met, produce an action plan aimed at improving the situation.