ASTM D8208-19

5.1 Exposures to high concentrations of aerosolized fine and ultrafine non-fibrous metal particles, including manganese (Mn), chromium (Cr), and nickel (Ni) generated during processes that involve high energy such as welding or smelting, may elicit deleterious health effects. Animal and epidemiological studies have associated welding and related work processes with a wide range of adverse health effects, including upper respiratory effects (rhinitis and laryngitis), pulmonary effects (pneumonitis, chronic bronchitis, decreased pulmonary function), potential neurological disorders (manganese-induced Parkinsonism), and high lung cancer and pneumoconiosis death rates. Manganese has been associated with neurological diseases.

5.2 Nanoparticles produced from metals, or their oxides and chalcogenides, have found many industrial uses. Examples of nanometals include silver (Ag), gold (Au), iron (Fe), copper (Cu), cadmium (Cd), zinc (Zn), platinum (Pt), and lead (Pd); examples of nanometal oxides include aluminium oxide (Al₂O₃), magnesium oxide (MgO), zirconium dioxide (ZrO₂), cerium(IV) oxide (CeO_{5.3 Aerosol sampling methods generally specify the collection of workplace air samples using inhalable and related samplers. These exposure assessment methods, as well as the use of respirable and thoracic samplers (ISO 7708), are inadequate for measurements of nanoparticle exposure when paired with gravimetric analysis. Large particles (>1 μm) weigh substantially more than nanoparticles typical of fumes and, consequently, obscure the ability to detect nanoparticles through gravimetric filter sampling. Additionally, most size-selective samplers collect all particles in the fraction of aerosol that can penetrate into the respiratory tract. Particle deposition, which is governed by the principles of impaction, interception, and diffusion (ISO 13138), is typically overestimated by these samplers.}

5.4 There is a need to measure nanoparticle airborne concentrations apart from larger particles. An NRD sampler selectively collects nanoparticles in a manner similar to their typical deposition in the human respiratory tract. The constant motion of nanoparticles causes them to diffuse and potentially deposit in all regions of the respiratory tract, from the head airways to the deep alveolar region, as described by the ICRP 5.5 Welding fumes are dominated by incidental nanoparticles (particles with any external dimension in the nanoscale), but also include larger particles generated by splatter. Current animal and epidemiological studies investigate exposure to welding fumes without differentiating between nanoparticles and larger particles. Welding fume nanoparticles have been found to induce more toxic effects at the cellular level and to generate more reactive oxygen species (ROS) activity when compared to larger particles.

5.6 An NRD sampler was initially designed with nylon screens as the diffusion stage for the collection of nanoparticles 5.7 A new diffusion stage substrate, polyurethane foam, has characteristics more closely resembling human airways (example, Ref 5.8 The sampler with polyurethane foam has been shown to mimic the ICRP deposition curve closely when sampling spherical nanoparticles up to 100 nm diameter. Agglomerated particles collected in foam begin to show significant deviations from the simple curve as their size and shape factor increase 5.9 An accurate measurement of flow rate through an NRD sampler is required for experiments where sampling devices and filter materials are to be compared as to the size distribution aerosol they capture. Air flow rate affects the efficiency with which a sampler will capture a particular aerodynamic size of particles. Furthermore, air flow rate through a sampler may affect the distribution of aerosol particles captured on the filters and deposited on the sampler collection substrates and walls. To determine aerosol concentration from a mass of captured particles it is necessary to set and measure flow rates accurately.

1.1 This practice describes specified apparatus and procedures for collection of non-fibrous airborne metal nanoparticles generated during work activities.

1.2 Nanoparticle respiratory deposition (NRD) samplers are designed to follow a nanoparticulate matter (NPM) deposition curve based on the International Commission on Radiological Protection (ICRP) model for deposition of particles smaller than 300 nm (the minimum deposition for submicrometre particles) while removing the larger particles (1).2

1.3 This practice is applicable to personal and area sampling during work processes and situations where metal nanoparticles may be generated (for example, welding, smelting, shooting ranges).

1.4 This practice is intended for use by professionals experienced in the use of devices for occupational air sampling (such as cyclone samplers).

1.5 This practice is not applicable to the sampling of fibrous nanoparticles such as carbon nanotubes.

1.6 Detailed operating instructions are not provided owing to differences among various makes and models of suitable devices and instruments. The user is expected to follow specific instructions provided by the manufacturers of particular items of equipment. This practice does not address comparative accuracy of different devices nor the precision between instruments of the same make and model.

1.7 This practice contains notes that are explanatory and are not part of the mandatory requirements of the method.

1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.