The majority of datasets listed in this portal are not directly curated by TOAR, and we assume no responsibility for the accuracy of the information provided. The TOAR Data Centre does not store copies of these datasets; instead, it provides links to data descriptions and data access points, and, where available, REST APIs (i.e. machine-readable interfaces). Contact information and data licence details are also included whenever available.

The only data physically stored at the TOAR Data Centre are surface air quality monitoring observations. These are compiled in a PostGIS database (the TOAR database), which has been developed to collect and harmonize extensive metadata on monitoring sites and air quality time series. The vast majority of these datasets were obtained through direct collaboration with environmental and research agencies around the world.

Although many of these datasets are freely available for download, access is not always straightforward, data formats vary considerably, and metadata are often missing or incomplete. These issues are addressed during the integration of the data into the TOAR database. We strive to maintain direct contact with data providers to stay informed about updates to their datasets and to report any issues that we identify. Nevertheless, no data collection is perfect, and we provide the data as is, without any guarantee.