Occupational exposure risk during spraying of biocidal paint containing silver nanoparticles

Abstract

The study assessed potential to exceed occupational exposure limits while spraying paint with and without a silver nanoparticle biocidal additive. A tradesperson performed the tasks in a sealed chamber with filtered air supply. Integrated air sampling entailed transmission electron microscopy with energy dispersive X-ray analysis, direct-reading of particle number concentrations, and determination of silver mass concentration by NIOSH Method 7300. Silver nanoparticles were primarily embedded in paint spray droplets but also observed as isolated particles. Using an α-level of 0.05, median nanoparticle number concentrations did not differ significantly when spraying conventional vs. biocidal paint, although statistically significant differences were observed at specific particle size ranges <100 nm. The geometric mean concentration of total silver while spraying biocidal paint (n = 6) was 2.1 µg/m³ (95% CI: 1.5–2.8 µg/m³), and no respirable silver was detected (<0.50 µg/m³). The results address a lack of silver nanoparticle exposure data in construction and demonstrate the feasibility of a practical sampling approach. Given similar conditions, the measurements suggest a low probability of exceeding a proposed silver nanoparticle exposure limit of 0.9 µg/m³ as an airborne 8-hr time-weighted average respirable mass concentration. A full workday of exposure to respirable silver at the highest possible level in this study (<0.50 µg/m³) would not exceed the exposure limit, although limitations in comparing short task-based exposures to an 8-hr exposure limit must be noted. There was airflow in the study chamber, whereas exposure levels could increase over time in work environments lacking adequate ventilation. Potential to exceed the exposure limit hinged upon the respirable fraction of the paint mist, which could vary by material and application method. Additional research would improve understanding of silver nanoparticle exposure risks among construction trades, and biological responses to these exposures. Given the potential for exposure variability on construction jobsites, safety and health professionals should be cognizant of methods to assess and control silver nanoparticle exposures.

Keywords:

• Coatings
• construction
• exposure limits
• nanomaterials
• painters

Acknowledgments

The authors have declared no conflicts of interest. The authors thank and acknowledge Dr. Jenny Roberts, Dr. Eun Gyung (Emily) Lee, and Dr. Aaron Erdely of NIOSH for their technical assistance and support; Spencer Schwegler, John Burcaw, and the International Union of Painters and Allied Trades for guidance on tool selection and work practices; and Franco Harris and Melanie Barton of SilverArmor Paints and Coatings for supplying the paints used in this study, answering questions about the products, and for being amenable to having the safety of their products evaluated by independent researchers. Any mention of specific companies or products does not imply that they are endorsed or recommended by CPWR or NIOSH. Opinions expressed are those of the authors and do not necessarily represent the official views of CPWR or NIOSH.

Additional information

Funding

The National Institute for Occupational Safety and Health (NIOSH) funded this study through a cooperative agreement (Number U60-OH009762) with The Center for Construction Research and Training (CPWR).