Developments in Inhalable Samplers
In 1982, ACGIH appointed an ad hoc committee on Air Sampling Procedures (ASP) with the task of preparing recommendations for size-selective sampling that would lead to an approach for establishing particle-size selective TLV's for particulate materials. Committee recommendations were first presented at the 1984 Annual ACGIH Membership Meeting and were later published by ACGIH in 1999. 1 In their recommendations, the ASP Committee opted for samplers "that would collect particles that would penetrate to, but not necessarily deposit in, the specific region of interest." 2
In 1993, revisions to Appendix D of the ACGIH TLV/BEI ® booklet, "Particle Size-Selective Sampling Criteria for Airborne Particulate Matter," were adopted by ACGIH ®. Three particulate mass fractions were defined:
1. Inhalable Particulate Mass
Those materials that are hazardous when deposited anywhere in the respiratory tract. This includes particulate matter that enters the head airways region including the nose and mouth, nasopharynx, oropharynx and laryngopharynx and those materials that can produce systemic toxicity from deposition anywhere in the respiratory system. Inhalable samplers were defined as having a collection efficiency of 50% (50% cut-point) at 100 microns.
2. Thoracic Particulate Mass
Those materials that are hazardous when deposited anywhere within the lung airways and the gas-exchange region. This includes particulate matter that enters the tracheobronchial region including the trachea, bronchi, and bronchioles. Thoracic samplers were defined as having a 50% cut-point at 10 microns.
3. Respirable Particulate Mass
Those materials that are hazardous when deposited in the gas-exchange region including the respiratory bronchioles and alveoli. A significant change from previous definitions, the 1993 recommendation increased the 50% cut-point for respirable dust samplers from 3.5 to 4.0 microns.