Comparative short-term inhalation toxicity of five organic diketopyrrolopyrrole pigments and two inorganic iron-oxide-based pigments

Abstract

Diketopyrrolopyrroles (DPP) are a relatively new class of organic high-performance pigments. The present inhalation and particle characterization studies were performed to compare the effects of five DPP-based pigments (coarse and fine Pigment Red 254, coarse and fine meta-chloro DPP isomer and one form of mixed chlorinated DPP isomers) and compare it to coarse and fine inorganic Pigment Red 101. Wistar rats were exposed head-nose to atmospheres of the respective materials for 6 h/day on 5 consecutive days. Target concentrations were 30 mg/m³ as high dose for all compounds and selected based occupational exposure limits for respirable nuisance dust. Toxicity was determined after end of exposure and after 3-week recovery using broncho-alveolar lavage fluid (BALF) and microscopic examinations of the entire respiratory tract. Mixed chlorinated DPP isomers and coarse meta-chloro DPP isomer caused marginal changes in BALF, consisting of slight increases of polymorphonuclear neutrophils, and in case of coarse meta-chloro DPP increased MCP-1 and osteopontin levels. Mixed chlorinated DPP isomers, Pigment Red 254, and meta-chloro DPP caused pigment deposits and phagocytosis by alveolar macrophages, slight hypertrophy/hyperplasia of the bronchioles and alveolar ducts, but without evidence of inflammation. In contrast, only pigment deposition and pigment phagocytosis were observed after exposure to Pigment Red 101. All pigments were tolerated well and caused only marginal effects in BALF or no effects at all. Only minor effects were seen on the lung by microscopic examination. There was no evidence of systemic inflammation based on acute-phase protein levels in blood.

Keywords:

• Diketopyrrolopyrrole
• inhalation toxicity
• iron oxide
• pigments
• short-term inhalation toxicity test

Acknowledgements

The authors thank Elke Wittmer, Ernst Bohrer, Stefan Rath, Sarah Koppenhagen, Annette Knecht, Sabine Löffler, Irmgard Weber, Jeanette Vogt, Ulrich Flörchinger and the Pathology team, for their excellent technical assistance in performing the inhalation study, the clinical and histopathological examinations, and Jasmin Athas (lab work on dispersibility and contact angle) and Arnaud Gandon (lab work and assay development of FRAS assay).

Declaration of interest

The authors are employees of BASF SE, a company producing and marketing DPP pigments and iron oxide. This work was sponsored by BASF SE.