Mould growth in archival and library collections can present a health hazard to those that access them. Spores, mycotoxins and microbial volatile organic compounds (MVOCs) produced by mould can cause both acute and chronic reactions. However, the extent of this risk is determined by several factors:
State
Mould growth may be active or inactive. To reproduce, mould requires an optimal environment of 10-35ºC and a relative humidity (RH) exceeding 65%. When disturbed by air movement or physical contact, mould releases spores into the surrounding area to form further mould colonies. Active mould can appear as fluffy or slimy growths, which may smear when touched.
Appearance and colour can vary according to species and substrate. Collection material and the surrounding storage environment may have a damp feel or musty odour. When RH decreases, mould becomes inactive. In this state, it may look like staining or mottling on the object surface, seeming desiccated, dry, powdery or crusty.
Mould can remain inactive for many years but will re-activate if ambient humidity creates a suitable environment. Typically, the majority of damage to historic collection material is caused by mould that is now inactive. As such, it is important to understand that although inactive mould does not pose an immediate risk to collection material, it does not lose its allergenic or toxigenic properties.
Quantity
The extent of mould presence may be limited to a small number of items only, or could affect substantial portions of the collection, as well as the storage space itself. The more extensive the infestation, the greater the risk to health.
Exposure
Exposure mechanisms such as inhalation, ingestion or skin contact may cause acute reactions, including sneezing, a runny nose, red or itchy eyes, and/or skin rashes, which can be difficult to distinguish from other illnesses. Twaroch et al, in their article on ‘Mold Allergens in Respiratory Allergy’, assert that the effects of exposure to mould are cumulative and between 3-10% of the population can develop an adverse reaction to it. Chronic reactions are typically species dependent. They are rare but serious, so exposure time should be limited, and mitigation measures employed (i.e. Personal Protective Equipment (PPE)).
Susceptibility
Individuals more susceptible to the effects of mould include those with eczema, asthma, respiratory or allergy problems. It is recommended that people suffering from severe immunity issues do not work with mould at all. It is also advised that pregnant women do not work with mould. Individuals who are aware they may be at risk should discuss this with their management.