First order risk assessment for nanoparticle inhalation exposure during injection molding of polypropylene composites and production of tungsten-carbide-cobalt fine powder based upon pulmonary inflammation and surface area dose

Inhalation exposure to low toxicity and biodurable particles has shown to induce polymorphonuclear neutrophilia (PMN) in the lungs, which is a strong indicator for lung inflammation. Recently, Schmid and Stoeger (2016) reviewed mice and rat intratracheal instillation studies and assessed the relation between particles dry powder BET surface area dose and PMN influx for granular biodurable particles (GBPs) and transition metal oxides. In this study, we measured workers alveolar lung deposited surface area (LDSA) concentrations (μm2 cm− 3) during injection molding of polypropylene (PP) car bumpers and production of tungsten-carbide-cobalt (WCCo) fine grade powder using diffusion chargers. First order risk assessment was performed by comparing the doses calculated from measured LDSA concentrations during an 8-h work day with the NOEL1/100, the one hundredth of no observed effect level, assigned for GBPs (0.11 cm2 g− 1) and transition metal oxide particles (9 × 10− 3 cm2 g− 1). During the injection molding of PP car bumpers, LDSA concentrations varied from 23 to 39.8 μm2 cm− 3. During 8-h exposure PP, particle doses were at a maximum of 1.4 × 10− 3 cm2 g− 1, which was a factor 100 lower compared to the NOEL1/100 assigned for GBPs. In the WCCo fine powder production plant, the LDSA concentrations were below 18.7 μm2 cm− 3, which corresponds to the 8-h dose of 2.7 × 10− 3 cm2 g− 1. This is 3 times lower than the NOEL1/100 assigned for transition metal oxide particles. The LDSA concentrations were generally low compared to urban background levels of 44.2 μm2 cm− 3 in European cities.

Source: Koivisto, A. J., Kling, K. I., Levin, M., Fransman, W., Gosens, I., Cassee, F. R., & Jensen, K. A. (2016). NanoImpact.

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