Particulate level, properties associated with

In the present work, such a systematic approach to the physical characterization of pharmaceutical solids is outlined. Techniques available for the study of physical properties are classified as being associated with the molecular level (properties associated with individual molecules), the particulate level (properties pertaining to individual solid particles), and the bulk level (properties associated with an ensemble of particulates). Acquisition of this range of physical information yields a total profile of the pharmaceutical solid in question, whether it is an active drug, an excipient, or a blend of these. The development of a total profile is a requirement for successful manufacture of any solid dosage form. 

Mechanical filtration systems are intended to limit the introduction of pollutants from outdoors to indoors. The efficiency of such systems generally depends on the filter properties and the aerodynamic properties of filtered particles [26]. The efficiency of filters varies from 5% to 40% for low-efficiency filters, such as dry media filters, panel and bag filters, from 60% to 90% for electrostatic precipitators to over 99% for high-efficiency particulate air filters. Not only the filters, but the whole heating, ventilation and air-conditioning system contributes to particle reduction, owing to particle losses on the cooling/heating coil and other parts of the system. The selection of a system depends on the type of indoor environment, outdoor and indoor sources, the demand on the level of reduction of pollutant concentrations and the cost associated with purchase, operation and maintenance of the system. 

Thus, the distinction between the hazard (an inherent toxic property of a chemical that may or may not be manifested, depending on exposure potential) and risk (the consequences of being exposed to a hazardous chemical at a particular exposure level) is critical (Purchase, 2000). Each component of a risk assessment—hazard identification, dose-response evaluation, and exposure assessment—is essential for evaluating the potential risks associated with the use of a substance such as a nanomaterial. The components of a risk assessment are universal in their application for assessing the hazards and risks of chemicals or products for a variety of industries or environmental exposures, regardless of the types of chemicals of interest (such as solvents, fibers, particulates and nanomaterials). 

Physical characterization can be performed at molecular, particulate, or bulk (macroscopic) levels. From the terminology cited by Brittain et al. (2), molecular properties are associated with individual molecules, particulate properties are considered as properties that pertain to individual solid particles, and bulk properties are those that are associated with an assembly of particulate species. Most reports in pharmaceutical literature cover characterization of bulk properties. 

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