Birmingham City Council said the scheme has improved air quality in the past year and reduced the most polluting traffic from 18.7% to 9.2% within the year.
In the first six months of the scheme, the levels of nitrogen dioxide in the city centre also fell by 13%.
Cllr Liz Clements, the council's cabinet member for transport, said: 'This month marks the first anniversary of Birmingham’s Clean Air Zone. I am pleased to say we have made good progress towards our goal of improving air quality in the city centre but we cannot rest on our laurels, so we are offering some additional support to help accelerate our journey to becoming a clean air city and to help improve the lives of everyone who lives and works in the city.'
The figures show that 98% of buses entering the Clean Air Zone meet the emissions standards. Vans make up nearly one in 10 of all vehicles that enter the CAZ, of which 79% meet the emissions standard.