Environmental data report September 1990 to August 1991.

The International Co-operative Programme on Effects on Materials, including Historic and Cultural Monuments has an extensive programme on material exposure in well defined environments. This report includes the environmental data from the fourth exposure year of temperature, relative humidity, time of wetness, sunshine hours, concentrations of SO2, NO2, O3, and precipitation amount and quality. The yearly results from the previous years are also reported and the quality of data has been evaluated.