Currently available human health research studies conclude that there is no evidence for a “safe” level of asbestos exposure, and thus that any quantity should be considered potentially dangerous. However, a health risk exists solely when asbestos fibres are released into the air and when the resulting contaminated air is inhaled into the lungs. Even then it appears that most people exposed to relatively small amounts of asbestos do not develop problems. The fact remains, however, that the chances of developing serious respiratory illnesses, including lung cancer, are greater in those exposed to airborne asbestos fibres.
Conversely, this correctly confers that many ACMs pose no health risk unless they are subject to physical or environmental disturbance. However, any ACM inside a building constitutes a hazard. It should be noted that hazard is a potential for harm, whereas risk is the probability that this potential may become actual. With this distinction, it is self-evident that a simple identification and analysis of asbestos containing materials (ACMs) is insufficient to gauge the degree of risk. Since it is the airborne fraction of asbestos that is dangerous, a major factor in assessing risk conditions is to have a knowledge and understanding of the design of the building in general and its air handling system. Thus, where appropriate, our building surveys include a review of the ventilation system layout and operation.
A qualitative risk evaluation provides information for assessing potential for fibre release of the asbestos and subsequent exposure of building occupants to asbestos containing materials. In order to set priorities, the qualitative risk assessment combines relevant qualitative and subjective factors to generate a numerical index for the potential asbestos hazard. Qualitative factors include condition at the time of the inspection, potential for physical change, the proximity to air currents and air plenums, and the degree of potential for occupant exposure to asbestos fibres. Subjective factors include friability and accessibility of the suspect material. The factors are compiled into overall indices which provide the risk assessment analyst with relative rather than absolute rankings of hazard potential.
Conclusions regarding risk/priority and recommendations for management are then based on the data generated.
Recognising the subjective nature of this assessment, care needs to be taken in ensuring that the inspectors are well trained and have extensive experience with these procedures.