Protesters fighting a controversial road closure in Isleworth have unearthed alarming data about pollution which they say supports their case.
Levels of harmful nitrogen dioxide (NO2), produced by vehicles, in Twickenham Road are nearly twice the legal limit, according to Hounslow Council's own figures.
Campaigners say closing nearby Church Street will add to congestion in Twickenham Road, which is home to West Middlesex Hospital and a number of schools, making the air there even filthier.
A report published by Hounslow Council in October shows NO2 levels at Busch Corner, at the junction of Twickenham Road and London Road, were 74.9 micrograms per cubic metre (µg/m3) in 2014.
That is nearly double the EU limit of 40µg/m3 and significantly higher than any of the other 35 sites across the borough monitored by the council.
Further down Twickenham Road, close to the junction with North Street, the annual mean concentration of NO2 was 41.1µg/m3, which is still in breach of EU regulations.
The council's figures, from its '2015 Air Quality Updating and Screening Assessment', show levels of the pollutant have risen in three of the last four years, from 61.8µg/m3 in 2010.
Dr Nichola Keay, who unearthed the statistics, is among those opposed to the 18-month trial closure of Church Street, which is due to begin on Monday (December 7).
"Given the council's own predictions that closing Church Street will increase delays in the area by 142%, it's inevitable pollution in Twickenham Road will become even worse," she said.
"I have asked the council's head of transport what the pollution threshold is at which Church Street would be re-opened but I have not received a reply."
The council has said it took the decision to close Church Street following complaints from residents about drivers using the narrow residential road as a "rat run" .
In a survey earlier this year about 60% of those responding supported the move, but critics say a wider area should have been consulted .
Campaigners are planning to march along Twickenham Road next weekend in protest at the closure.
On the same day, residents of Church Street are holding a Christmas party to celebrate their road being closed to through traffic.
