Inhalation of
beryllium dusts generated during milling of ores and cutting of
beryl-containing gemstones is associated with development of
beryllium sensitization and low prevalence of chronic
beryllium disease (CBD). Inhalation of
beryllium aerosols generated during primary
beryllium production and machining of the
metal,
alloys, and ceramics are associated with sensitization and high rates of CBD, despite similar airborne
beryllium mass concentrations among these industries. Understanding the physicochemical properties of exposure
aerosols may help to understand the differential immunopathologic mechanisms of sensitization and CBD and lead to more biologically relevant exposure standards. Properties of
aerosols generated during the industrial milling of bertrandite and
beryl ores were evaluated. Airborne
beryllium mass concentrations among work areas ranged from 0.001 microg/m(3) (
beryl ore grinding) to 2.1 microg/m(3) (
beryl ore crushing). Respirable mass fractions of airborne
beryllium-containing particles were < 20% in low-energy input operation areas (ore crushing,
hydroxide product drumming) and > 80% in high-energy input areas (
beryl melting,
beryl grinding). Particle specific surface area decreased with processing from feedstock ores to drumming final product
beryllium hydroxide. Among work areas,
beryllium was identified in three crystalline forms:
beryl, poorly crystalline
beryllium oxide, and
beryllium hydroxide. In comparison to
aerosols generated by high-CBD risk primary production processes,
aerosol particles encountered during milling had similar mass concentrations, generally lower number concentrations and surface area, and contained no identifiable highly crystalline
beryllium oxide. One possible explanation for the apparent low prevalence of CBD among workers exposed to
beryllium mineral dusts may be that characteristics of the exposure material do not contribute to the development of lung burdens sufficient for progression from sensitization to CBD. In comparison to high-CBD risk exposures where the chemical nature of
aerosol particles may confer higher bioavailability, respirable ore dusts likely confer considerably less. While finished product
beryllium hydroxide particles may confer bioavailability similar to that of high-CBD risk
aerosols, physical exposure factors (i.e., large particle sizes) may limit development of alveolar lung burdens.