Suppression and dispersion of airborne dust and nanoparticulates

The inhalation of particulate matter (PM) represents a significant health concern. As a result, the United States Environmental Protection Agency has instituted a number of PM standards to minimize emission levels. These standards have been developing for the past three decades as our understanding of PM exposure and adverse health effects increases. It has been believed that dust suppression has been "beaten to death." However, it is still unclear how effective suppression and exposure validation can be achieved. Two ways to address PM exposure is firstly develop methods to reduce PM emissions (though suppression) and secondly understand the nature and propagation of PM to minimize exposure.; It has been reported that the most effective reagents are those which improve the wetting characteristics of the material. However, no studies have been done which clearly show a relationship between wetting enhancement and PM suppression. Furthermore, it has not been established what type of wetting behavior such as: low wetting contact angle, rapid particle engulfment, effective surface area coverage, and easy suppressant soakabiltiy is critical for achieving effective PM suppression. Other issues such as interparticle adhesion and repulsive forces have been identified as possible factors in PM suppression, but have not correlated with PM emissions. Still other factors such as suppressant longevity should also be considered in achieving effective PM suppression for periods of time. Therefore, there was a tremendous need to conduct systematic studies which examined these factors for different materials under varying conditions. Under some conditions, the extent of wetting and suppressant longevity may be an issue while in others (kinetic situations) the actual wetting rate may play a role. Therefore, the selection of a suitable PM suppressant has to account for the specific conditions which exist.; Another critical aspect of PM involves the fundamental behavior of the particles when they are released into the air. This behavior has a significant impact on their propagation and thus has an impact on the exposure levels which are present. Several mathematical approaches have been developed to model the propagation of PM, but it has not been established through observation what factors dictate the propagation phenomena. This aspect of PM control will also be presented.