Exposure to thermal spraying

In thermal spraying, the material to be applied is melted and applied to a substrate under high pressure. It often concerns metal products with which vapor and dust are created. The question is how high exposure to these and other products can be.

Exhibition studies

The systematic review by Antonini et al. (2020) provides an overview of a number of studies into the level and nature of exposure with thermal spraying. Not much research appears to have been done to date. Measurements with thermal spraying have been found to lead to very high concentrations in the air, of both particles and the metals used (Bemer et al. 2010, Huang et al. 2016).

Image by Sabine Hueber from Pixabay

This exposure is also significantly higher than for welding. In addition, employees who clean or maintain the spray booth may be highly exposed (Petsas et al. 2007). When carefully working with the right personal protective equipment in good spray booths, the values ​​can be much lower (Petsas et al. 2007)

Measurement is rather complicated due to the clumping of small particles, as can also occur with welding fumes (Bemer et al. 2010). The large percentages of very small particles (nanoscale, particulate matter) that are generated in the various processes are worrying. (Bemer et al. 2010; Viana et al. 2017; Salmatonidis et al. 2019).

The article describes the most important of the rare articles with research on exposure and health risks:

StudyFindings
Chadwick et al. (1997)Increased urine concentrations of chromium, nickel, and cobalt in workers who thermo spray.
Washington State Department of Labor
and Industries (2005)
Employee died of severe lung damage from inhalation of toxic metals during thermal spraying.
Petsas et al. (2007)Increased particle concentrations during cleaning and maintenance of thermal spray booths.
Bemer et al. (2010)The emissions from thermal spraying are much higher than from welding
Huang et al. (2016)

Total dust concentrations in thermal spraying exceed the local limit values ​​four to eight times
Viana et al. (2017)Increased generation of ultra-fine particles inside and outside the spray booth.
Salmatonidis et al. (2019, 2020)90% of the particles formed in thermal spraying are smaller than 90 nm.

Biomonitoring

I only found one article in which biological monitoring in the urine was carried out with thermal spraying. In 1997 Chadwick et al. Examined 34 thermal spray workers in Great Britain. They worked with cobalt, chrome and nickel, among other things. He found cobalt concentrations of 20–30 µg / m in environmental measurements3 and in the urine or 10–20 µmol / mol creatinine. This was 10-20 times higher than for the unexposed workers.

Conclusion

Antonini et al. (2020) conclude that exposure via thermal spraying is an emerging health risk about which not enough is known due to a lack of research. In particular, the high degree of ultra-fine particles that are generated in this process and the use of various metals create risky situations. All the more because biomonitoring has already shown that employees actually ingest these metals.

Sources

Antonini, JM, McKinney, WG, Lee, EG, & Afshari, AA (2020). Review of the physicochemical properties and associated health effects of aerosols generated during thermal spray coating processesToxicology and Industrial Health, 0748233720977975.

Bémer, D., Régnier, R., Subra, I., Sutter, B., Lecler, MT, & Morele, Y. (2010). Ultrafine particles emitted by flame and electric arc guns for thermal spraying of metals. Annals of Occupational Hygiene, 54 (6), 607-614.

Petsas, N., Kouzilos, G., Papapanos, G., Vardavoulias, M., & Moutsatsou, A. (2005, September). Levels and Composition of Suspended Particles in a Thermal Spray Industry. In 7th World Congress on Recovery, Recycling and Re-integration (pp. 25-29).

Petsas, N., Moutsatsou, A., Papapanos, G., Economou, S., Vardavoulias, M., Pantelis, DI, & Sarafoglou, CI (2006). Nanophased thermal sprayed alloyed steel coatings for diesel engine components. BOOK INSTITUTE OF MATERIALS, 807, 439.

Petsas, N., Kouzilos, G., Papapanos, G. et al. Worker Exposure Monitoring of Suspended Particles in a Thermal Spray Industry† J Therm Spray Tech 16, 214–219 (2007).

Chadwick JK, Wilson HK, White MA. An investigation of occupational metal exposure in thermal spraying processes. Sci Total Environ. 1997 Jun 20; 199 (1-2): 115-24. doi: 10.1016 / s0048-9697 (97) 05487-9. PMID: 9200854.

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