Identification of diniobium pentaoxide as a novel nuisance dust in a 90-day nose-only inhalation study

Objective: The presence of fine dusts in the industrial working environment has significant implications for occupational safety. As a result, legislators have implemented regulations to protect employees from adverse lung effects. The establishment of limits aims to prevent health hazards, particularly lung diseases, even with prolonged exposure. Niobium, a chemical element widely used in the industry, is commonly found as an additive in various alloy products. Materials and Methods: Given the inhalation potential during manufacturing and the substantial volume of niobium used, a 90-day-nose-only inhalation study of diniobium pentaoxide (Nb2O5) was conducted in rats. Following exposure of rats to 1.5, 6, and 24 mg/m3 Nb2O5, various endpoints were examined to assess potential lung toxicity and exposure–concentration–response relationships associated with the inhaled test substance. Results: Analysis of polymorphonuclear neutrophils (PMNs) in bronchoalveolar lavage fluid (BALF) in the treated groups showed levels close to clean air control levels. Histopathological analysis revealed the presence of particle-laden macrophages in lung alveoli, bronchus- and nose-associated lymphoid tissue, and lung-associated lymph nodes in the group exposed to the highest concentration. Additionally, activation of pneumocytes type 2 was observed. Discussion and Conclusions: All findings were interpreted as adaptive and non-adverse. Therefore, no adverse effects were observed in any of the endpoints, including the group exposed to the highest concentration. Under the conditions of this study, a NOAEC (no observed adverse effect concentration) of 24 mg/m3 was determined. Diniobium pentaoxide is thus considered a newly discovered nuisance dust.