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

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.

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.

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.

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.