All data is given in the corresponding ICP Materials reports, which are available as PDFs for download at this site.

A complete meta data description was published in 2012 (open access), covering exposures performed during the period 1987-2009:

Tidblad et al. Effects of Air Pollution on Materials and Cultural Heritage. ICP Materials Celebrates 25 Years of Research, International Journal of Corrosion 2012, ID 496321
    Link to Publisher (Hindawi)

After that, one year exposures have been performed 2011-2012 and 2014-2015 and four year exposures 2011-2015. A paper with one and four year data including selected sites with the most available data was published in 2017 (open access), covering exposures performed during the period 1987-2015:

Report 82 Trends in Pollution, Corrosion and Soiling 1987-2014

Tidblad et al. ICP Materials Trends in Corrosion, Soiling and Air Pollution (1987-2014), Materials 2017, 10(8), 969
    Link to Publisher (MDPI)
    Data (XLS), supplementary material

The current plan for exposures include one year exposures 2017-2018 and 2017-2021, four year exposures 2017-2021 and eight year exposures of weathering steel 2011-2019.

Updated 11/01/2018