In March 2018 we updated the Search by Location and Site Relevant Critical Loads tools in APIS to use background pollution maps based on a 3-year average for 2014-2016. An error has been discovered with the underlying gas and particulate matter monitoring data upon which the background maps are based. This affects the results for only the year 2016. It is probable that the 3-year average will be affected only slightly, however, the 2016 mapping is currently being re-run to quantify changes. As a precautionary measure for the meantime, we have reverted back to the 2013-2015 datasets in APIS and will re-issue the 2014-2016 maps as soon as they are available. The source attribution data in the Site Relevant Critical Loads tool has not been changed and continues to be based on 2012 emissions data.