Inhalation exposure during spray application and subsequent sanding of a wood sealant containing zinc oxide nanoparticles

Abstract

Nano-enabled construction products have entered into commerce. There are concerns about the safety of manufactured nanomaterials, and exposure assessments are needed for a more complete understanding of risk. This study assessed potential inhalation exposure to ZnO nanoparticles during spray application and power sanding of a commercially available wood sealant and evaluated the effectiveness of local exhaust ventilation in reducing exposure. A tradesperson performed the spraying and sanding inside an environmentally-controlled chamber. Dust control methods during sanding were compared. Filter-based sampling, electron microscopy, and real-time particle counters provided measures of exposure. Airborne nanoparticles above background levels were detected by particle counters for all exposure scenarios. Nanoparticle number concentrations and particle size distributions were similar for sanding of treated versus untreated wood. Very few unbound nanoparticles were detected in aerosol samples via electron microscopy, rather nano-sized ZnO was contained within, or on the surface of larger airborne particles. Whether the presence of nanoscale ZnO in these aerosols affects toxicity merits further investigation. Mass-based exposure measurements were below the NIOSH Recommended Exposure Limit for Zn, although there are no established exposure limits for nanoscale ZnO. Local exhaust ventilation was effective, reducing airborne nanoparticle number concentrations by up to 92% and reducing personal exposure to total dust by at least 80% in terms of mass. Given the discrepancies between the particle count data and electron microscopy observations, the chemical identity of the airborne nanoparticles detected by the particle counters remains uncertain. Prior studies attributed the main source of nanoparticle emissions during sanding to copper nanoparticles generated from electric sander motors. Potentially contrary results are presented suggesting the sander motor may not have been the primary source of nanoparticle emissions in this study. Further research is needed to understand potential risks faced by construction workers exposed to mixed aerosols containing manufactured nanomaterials. Until these risks are better understood, this study demonstrates that engineering controls can reduce exposure to manufactured nanomaterials; doing so may be prudent for protecting worker health.

Occupational exposure to nanoparticles originating from welding – case studies from the Czech Republic

“…With regard to the preliminary literature review of exposure studies to incidental nanoparticles in the manufacturing industry, which was conducted by the authors, specific companies in the Czech Republic with expected incidental nanoparticle exposure had been identified and contacted via e-mail, telephone and in person [9,[11][12][13][14][15][16][17][18][19][20]. Subsequently, a field survey was carried out.…”

“…Nanoparticles that can occur in the working environment include the following: metal nanoparticles, carbon black, nanoparticles from materials used and produced during ceramic sintering (clay, kaolin, iron and silicon oxides, ceramics, porcelain) colored pigments (metal oxides), gypsum, cements, combustion emissions, particles released during paper manufacturing, wood and plastic nanoparticles, spray mixtures containing ZnO, composite materials (containing epoxy resin, 'nano' component, glass and carbon fibers), mixtures with nano-constituents such as TiO 2 , SiO 2 , Al 2 O 3 , and carbon nanotubes [9,[11][12][13][14][15][16][17][18]. The most common working activities that may accidentally release nanoparticles are machining (milling, turning, drilling, grinding, cutting), arc welding, spraying, surface treatment application, combustion processes, bulk material handling (mixing, packaging), melting and casting of metals [7,9,11,13,16,19].…”

Transformation of zinc oxide nanoparticles in synthetic lung fluids

“…The generation of the aerosolized NPs will increase the potential for inhalation by the applicant [ 27 ]. The concentration of NPs present in the aerosolized product can enable exposure to high doses of NPs and NP additives, primarily via inhalation [ 28 ]. Consumer safety practices, including poor protective equipment during application, increases the likelihood of product inhalation [ 28 , 29 ].…”

An Evaluation of On-Tool System for Sanding Dust Collection: Pilot Study

“…Dust particles generated at the sanding process are drawn into housing by an airflow caused by the rotation of the fan, and they are exhausted from the housing through duct into the dust collector (such as filter bag, dust box or container). Several researchers have examined performance of dust separation units during grinding metal [2,5,13,21,27,29], sandstone [10], concrete [1], stone [10,14] or sanding drywall [28] and wood [3,9,15,18,19,20,24,26].…”