As FSP is a fraction of RSP, they share similar emission sources and emission trends. Between 2001 and 2018, FSP emissions decreased by 54%. Navigation, other combustion and non-combustion sectors were the top three sources of FSP emissions, accounting for 41%, 19% and 16% of total FSP emissions in 2018, respectively.
Similar to RSP, FSP originates from both local and regional emission sources and the roadside FSP emissions have been significantly reduced over the years.