The requirement is for the production of 1 km spatial resolution exposure surfaces for various indicators,chemical constituents and emission source sectors related to the air pollutant PM2.5 with coverage of all ten provinces of Canada during the period of 2000-2022. Surfaces are to be be developed using an atmospheric model with emission, satellite and ground based measurement data inputs. Health Canada is the client department.The contract will begin in the fall of 2021 and be completed in February 2024, with potential option years during FY’s 2024/2025 and 2025/2026. Project tasks will be delivered semi-annually and interim payments made on the same schedule. Tasks include the development of:a) bi-weekly and annual PM2.5 mass and component concentrations at a 1 km spatial resolution for all 10 provinces in Canada for 2000-2020.b) Develop bi-weekly and annual, 1 km resolution estimates of particle oxidative aging for 2000-2020.c) Develop monthly, seasonal, and annual, 1 km resolution estimates of PM2.5 mass and PM2.5 component concentrations attributed to at least 7 major emissions source sectors across all 10 provinces in Canada and the contiguous US.d) Provide updates to the PM2.5 mass and component concentrations (item a), and particle oxidative aging (item b) exposure surfaces for 2021-2022.e) Two additional option to develop and apply a methodology for estimating individual, ambient particulate-phase trace metals concentrations for at least 10 metals on a monthly and annual basis for all 10 provinces in Canada.