Physicochemical Characteristics of Aerosol Particles Generated During the Milling of Beryllium Silicate Ores: Implications for Risk Assessment

Abstract

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.

Release of beryllium from mineral ores in artificial lung and skin surface fluids

“…Development of CBD is associated with formation of granulomas in the lung alveoli over a period of years (Sawyer and Maier 2011). Hence, whether the reason that CBD has not yet been diagnosed among persons exposed to mineral forms of beryllium is because the solubility rate is too slow to sustain an immune reaction or because aerosols in work areas such as ore crushing are too large (Stefaniak et al 2008) to penetrate to the alveoli remains unanswered at this time.…”

“…The calculated mass median diameters were 25 lm (Monitor pit) and 26 lm (Blue Chalk pit), corresponding to an aerodynamic equivalent diameter of approximately 40 lm. At the mill in Utah, the mass median aerodynamic diameter of airborne dust in the bertrandite ore crushing work area is 10.5 lm (Stefaniak et al 2008). Hence, the size of the prepared ore powders was sufficient to be inhaled by workers and included sizes observed in the workplace atmosphere.…”

Development and Evaluation of Optimized Sucrose Ester Stabilized Oleanolic Acid Nanosuspensions Prepared by Wet Ball Milling with Design of Experiments

“…9 Significantly different compared with EAC. 10 Significantly different compared with EAD. 11 Significantly different compared with EBC.…”

“…5,6) Other reported pharmacological activities include anti-inflammatory, 7) antimicrobial activity, 8) hypolipidemic and anti-diabetic effects. 9) However, the low bioavailability of OA limits its application.…”

“…10,11) The formation of nanosuspension (NS) increased the surface area of a drug due to reduced particle size can improve drug dissolution rate and is often accepted as one of the most expeditious and cost-effective method to improve the dissolution properties of poorly water-soluble drugs. Wet ball milling is a common top-down method to prepare NS.…”