"Data from the UK National Atmospheric Emissions Inventory
indicate that particles from brake wear, tyre wear and road surface wear currently constitute
60% and 73% (by mass), respectively, of primary PM2.5 and PM10 emissions from road
transport, and will become more dominant in the future. Currently they contribute 7.4% and
8.5% of all UK primary PM2.5 and PM10 emissions. Therefore to achieve further gains in PM2.5
and PM10 air quality in relation to road transport sources requires attention to reducing non-
exhaust emissions, not solely a focus on lowering exhaust emissions.
The magnitudes of non-exhaust emissions are, however, highly uncertain, particularly when
compared to data for exhaust emissions."
From "Report: Non-Exhaust Emissions from Road Traffic" (https://uk-air.defra.gov.uk/library/reports.php?report_id=99...)
"Data from the UK National Atmospheric Emissions Inventory indicate that particles from brake wear, tyre wear and road surface wear currently constitute 60% and 73% (by mass), respectively, of primary PM2.5 and PM10 emissions from road transport, and will become more dominant in the future. Currently they contribute 7.4% and 8.5% of all UK primary PM2.5 and PM10 emissions. Therefore to achieve further gains in PM2.5 and PM10 air quality in relation to road transport sources requires attention to reducing non- exhaust emissions, not solely a focus on lowering exhaust emissions.
The magnitudes of non-exhaust emissions are, however, highly uncertain, particularly when compared to data for exhaust emissions."