Indoor/outdoor particulate matter concentrations and microbial load in cultural heritage collections

Mihalis Lazaridis,I Kopanakis,E Katsivela,L Raisi,G Panagiaris

doi:10.1186/s40494-015-0063-0

Abstract

Particulate matter, microorganisms in air and environmental conditions present a potential risk to museum collections. There are also limited studies of simultaneous measurements of airborne particles and microorganisms inside museums and the effects of seasonal variations. Therefore, extensive indoor/outdoor measurements of particulate matter mass/number concentrations and viable, cultivable microbial load were performed in two museums and a library in Greece for a period of 2 years at selected time intervals. The culture heritage collections are located at coastal (Historical Museum of Crete in Heraklion), urban (Criminology Museum of the University of Athens) and mountainous (Neophytos Doukas Library in Zagori) environments and their collections consist mainly of organic materials. Measurements of inhalable particulate mass (PM10, PM2.5, PM1) and viable, cultivable airborne microorganism concentrations (heterotrophic bacteria, cellulose metabolizing bacteria, acid producing bacteria and mesophilic fungi) in air were performed. The indoor PM10 and microbial concentrations were higher than the outdoor levels showing the influence of the indoor sources, such as the presence of people and indoor activities, as well as, anthropogenic outdoor sources, and natural emissions. Elevated PM1 particle number concentrations were also encountered in the Historical Museum of Crete in Heraklion and the Criminology Museum of the University of Athens due to the high anthropogenic emissions of the urban areas. The lowest concentrations of viable, cultivable airborne microorganisms were measured in the Historical Museum of Crete at the coastal site, which encounters also well controlled microclimatic conditions. In comparison to the other two naturally ventilated sites, the highest concentrations of viable, cultivable airborne fungi were measured in the Neophytos Doukas Library at the mountainous site, whereas the highest concentrations of viable, cultivable airborne heterotrophic bacteria were measured in the Criminology Museum of the University of Athens at an urban site, where mummified tissues and dry specimens are exhibited. The closed showcases of the two museums and the library could only protect the exhibits from viable, cultivable airborne fungi, but not from specific categories of bacteria. Acid producing bacteria in the Historical Museum of Crete, cellulose metabolizing bacteria in the Neophytos Doukas Library, and opportunistic pathogenic heterotrophic bacteria in the Criminology Museum of the University of Athens showed to be enriched inside the closed showcases.

Highlights

Particulate matter, microorganisms in air and environmental conditions present a potential risk to museum collections
The current study reports on particulate matter mass and number concentrations, viable, cultivable airborne microorganism concentrations, as well as, environmental conditions in two museums and a library in Greece for a period of 2 years
The lowest particulate matter concentrations outdoors were observed at the Neophytos Doukas Library in Zagori which is located in a mountainous region at the north west of the Greek mainland, whereas the highest particle levels indoors are measured in the Criminology Museum of the University of Athens

Summary

Introduction

Particulate matter, microorganisms in air and environmental conditions present a potential risk to museum collections. Extensive indoor/outdoor measurements of particulate matter mass/number concentrations and viable, cultivable microbial load were performed in two museums and a library in Greece for a period of 2 years at selected time intervals. Measurements of inhalable particulate mass (PM10, PM2.5, PM1) and viable, cultivable airborne microorganism concentrations (heterotrophic bacteria, cellulose metabolizing bacteria, acid producing bacteria and mesophilic fungi) in air were performed. The viable, cultivable microorganism load (bacteria and fungi) in the air inside museums has been identified as a major problem for the deterioration of cultural heritage objects [8]. Organic materials are very complex in structure and their deterioration is a complicated process. Besides the importance of thermal or photochemical induced oxidation process, ionic hydrolysis reactions and reactions induced by UV, there are several other factors which affect the deterioration of organic objects. All the reactions create changes in the organic structure caused by alterations in the chemical bonding and may lead to a disintegration of an object [1, 4]

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Conclusion