The majority of London’s traffic emission not from vehicle exhausts

“…about 88 per cent of London’s road traffic emission now arises from vehicle brake and tyre wear and resuspension…”

Transport for London Report 10

see the bottom of page 12, and figure 6.22 and the following text on page 163:

“Although London now complies with limit values for PM10, continued reductions to
ambient concentrations will bring further significant health benefits. Achieving this is
however difficult, given that , with only limited
technological options for improvement currently available. In 2016, London’s road
traffic PM10 emission was effectively unchanged; some small reductions arising
from the natural turnover of the vehicle fleet were offset by increased emissions
reflecting the overall increase in road traffic levels. ”