Metadata for file TWP_CO2_ratio_EMI.nc
This netcdf file contains gridded (0.5 degrees resolution) of TSM emissions of TWPs. The emission inventory has been calculated with the CO2 ratio method. The name of the variable is "MP_2014" and it is given in tonnes/year and total annual emissions of TSP TWPs are 3473 kt/year.

Metadata for file TWP_BWP_GAINS_EMI.nc
This netcdf file contains gridded (0.5 degrees resolution) of TSM emissions of TWPs and BWPs, which have resulted from the GAINS model. The names of the variables are "emis_tyre_TSP_HEG" and "emis_brake_TSP_HEG", respectively, given in kt/year. Total annual emissions of TSP TWPs and TSP TWP are 2379 kt/year and 174 kt/year.

Metadata for 1.flexout_CO2_ratio_TWP_0.5um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for TWPs with diameter 0.5 um using the emissions calculated with the CO2 ratio method. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 2.flexout_CO2_ratio_TWP_1.0um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for TWPs with diameter 1.0 um using the emissions calculated with the CO2 ratio method. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 3.flexout_CO2_ratio_TWP_2.1um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for TWPs with diameter 2.1 um using the emissions calculated with the CO2 ratio method. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 4.flexout_CO2_ratio_TWP_3.2um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for TWPs with diameter 3.2 um using the emissions calculated with the CO2 ratio method. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 5.flexout_CO2_ratio_TWP_6.0um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for TWPs with diameter 6.0 um using the emissions calculated with the CO2 ratio method. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 6.flexout_CO2_ratio_TWP_9.5um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for TWPs with diameter 9.5 um using the emissions calculated with the CO2 ratio method. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 1.flexout_GAINS_TWP_0.5um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for TWPs with diameter 0.5 um using the emissions calculated with the GAINS model. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 2.flexout_GAINS_TWP_1.0um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for TWPs with diameter 1.0 um using the emissions calculated with the GAINS model. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 3.flexout_GAINS_TWP_2.1um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for TWPs with diameter 2.1 um using the emissions calculated with the GAINS model. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 4.flexout_GAINS_TWP_3.2um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for TWPs with diameter 3.2 um using the emissions calculated with the GAINS model. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 5.flexout_GAINS_TWP_6.0um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for TWPs with diameter 6.0 um using the emissions calculated with the GAINS model. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 6.flexout_GAINS_TWP_9.5um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for TWPs with diameter 9.5 um using the emissions calculated with the GAINS model. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 1.flexout_GAINS_BWP_0.5um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for BWPs with diameter 0.5 um using the emissions calculated with the GAINS model. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 2.flexout_GAINS_BWP_1.0um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for BWPs with diameter 1.0 um using the emissions calculated with the GAINS model. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 3.flexout_GAINS_BWP_2.1um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for BWPs with diameter 2.1 um using the emissions calculated with the GAINS model. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 4.flexout_GAINS_BWP_3.2um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for BWPs with diameter 3.2 um using the emissions calculated with the GAINS model. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 5.flexout_GAINS_BWP_6.0um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for BWPs with diameter 6.0 um using the emissions calculated with the GAINS model. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

Metadata for 6.flexout_GAINS_BWP_9.5um.nc
The file contains simulation results (0.5 degrees spatial resolution, 1 day temporal resolution) for three (3) particle species (spec001, spec002, spec003) for BWPs with diameter 9.5 um using the emissions calculated with the GAINS model. Each species has different in-cloud scavenging properties (low, medium, and high CCN/IN efficiency). There are three (3) variables per species (9 in total) for concentration (spec001_mr, spec002_mr, spec003_mr), wet deposition (WD_spec001, WD_spec002, WD_spec003) and dry deposition (DD_spec001, DD_spec002, DD_spec003).

*** In all simulations, emissions for PM10 have been assumed independently on the size. Then the concentrations and deposition for each variable size are scaled accordingly. We assumed that 2.5%, 5%, 10%, 20% and 40% of the total TWPs and 60%, 70%, 80%, 90% and 100% of the total BWPs is PM10 and then calculated the geometric mean and geometric standard deviation. Accordingly, 0.25%, 0.5%, 1%, 2% and 4% of total TWPs and 30%, 40%, 50%, 60% and 70% of total BWPs were assumed PM2.5, based on the range of values reported in the literature. The concentration and deposition variables are scaled accordingly for PM10 particles, assuming that all 6 species participate in this size bin, and for PM2.5, assuming that species with sizes 0.5, 1.0 and 2.1 um are within this size mode. Then we applied a range of different a posteriori weightings of these size classes (eight for each size bin) presented in Extended Data Fig. 3. Hence, the results are based on the following number of ensemble members:
PM2.5: 5 emissions assumptions x 8 weighting for the size classes (three for PM2.5) x 3 species for different CCN/IN efficiency = 120 members
PM10: 5 emissions assumptions x 8 weighting for the size classes (six for PM10) x 3 species for different CCN/IN efficiency = 120 members

Metadata for lsm_mask.nc
Land-sea mask (0.5 degrees resolution) used in the calculations for the fraction that were deposited in land and ocean.

Metadata for ocean_mask.nc
Ocean mask 0.5 degrees resolution, that was used to calculate deposition and transport efficiencies of road microplastics,. The variable "basin" separates the following sea regions: Atlantic Ocean, Pacific Ocean , Indian Ocean, Mediterranean Sea, Baltic Sea, Black Sea, Red Sea, Persian Gulf, Hudson Bay, Southern Ocean, Arctic Ocean, Sea of Japan, Kara Sea, Sulu Sea, Baffin Bay, East Mediterranean, West Mediterranean, Sea of Okhotsk, Banda Sea, Caribbean Sea, Andaman Basin, North Caribbean, Gulf of Mexico, Beaufort Sea, South China Sea, Barents Sea, Celebes Sea, Aleutian Basin, Fiji Basin, North American Basin, West European Basin, Southeast Indian Basin, Coral Sea, East Indian Basin, Central Indian Basin, Southwest Atlantic Basin, Southeast Atlantic Basin, Southeast Pacific Basin, Guatemala Basin, East Caroline Basin, Marianas Basin, Philippine Sea, Arabian Sea, Chile Basin, Somali Basin, Mascarene Basin, Crozet Basin, Guinea Basin, Brazil Basin, Argentine Basin, Tasman Sea, Atlantic Indian Basin, Caspian Sea, Sulu Sea II, Venezuela Basin, Bay of Bengal, Java Sea, East Indian Atlantic Basin.

Metadata for cont_mask.nc
Country and continental masks in 0.5 degrees resolution that were used in the calculations of continental emissions, deposition and transport efficiencies.

Metadata for ECMWF_lsm_si_720x180_2014_daily.nc
Monthly sea-ice area fraction (siconc) and snow depth (sd) in 0.5 degrees resolution that were used to mask areas covered with sea-ice. The data were retrieved from European Centre for Medium Range Weather Forecast (ECMWF).

Metadata for ECMWF_precip_720x180_2014_daily.nc
Daily snowfall (sf) and total precipitation (tp) in 0.5 degrees resolution that were used to calculate snow concentrations of road microplastics. The dataset was retrieved from European Centre for Medium Range Weather Forecast (ECMWF) operational analyses.