Proposal for an integrated approach to microbial environmental monitoring in cultural heritage: experience at the Correggio exhibition in Parma

Microbial environmental monitoring represents one of the most useful methods to assess potential risks related to the integrity of cultural heritage and people's health. The monitoring plan described in the present work is based on standardized techniques for measuring microbial air and surface contamination. Air contamination is assessed through both active and passive samplings, measuring the concentration of microbes in air (in colony forming units per cubic metre, CFU/m(3)) and the rate at which microorganisms settle on surfaces (expressed by the Index of Microbial Air Contamination, IMA, CFU/dm(2)/h). For surface contamination, two parameters are measured using nitrocellulose membranes: the Microbial Buildup (MB, the total number of microorganisms accumulated on a surface in an unknown period of time prior to the sampling) and the Hourly Microbial Fallout (HMF, the number of microorganisms that settle on a specific surface during 1 h). The monitoring plan was implemented at the Pilotta Palace in Parma, Italy, during the Correggio exhibition in 2009. Samplings were taken before and during opening times. Some microbial contamination was already detected before the arrival of visitors: air contamination mean values of 99.1 CFU/m(3) and 5.2 CFU/dm(2)/h were recorded, while MB and HMF mean values for surfaces were 92 and 7 CFU/dm(2), respectively. A significant increase was recorded in air contamination during opening times, with mean values of 323.7 CFU/m(3) and 19.4 CFU/dm(2)/h; surface contamination values increased as well. This monitoring plan represents a contribution towards the definition of a much needed standardized methodology.