No pathogenic responses in rat lung upon exposure to ground granulated blast furnace slag (GGBS)

Objective: Granulated blast furnace slag (GBS) is a by-product of the manufacture of iron by thermochemical reduction in a blast furnace. Blast furnace slag is generated at temperatures above 1500 °C. If the liquid slag is quenched very rapidly with water, a glassy slag is generated (GBS). It is used - after grinding <100 µm - [ground granulated blast furnace slag (GGBS)] for cement and concrete production. A small particulate fraction of GGBS might be accessible to the pulmonary alveoli, where it could settle down and induces physiological inflammatory responses. Within the scope of the 'Registration, Evaluation, Authorization and Restriction of Chemicals' (REACH), GGBS was already tested in rats in an acute toxicity inhalation study, as well as in a dose range finding study as a predecessor study for this study. Both did not show systemic and local toxic effect in rats upon inhalation of high-dose GGBS.Material and methods: In this study, low (4.3 mg/m³), intermediate (9.5 mg/m³), and high-dose (24.9 mg/m³) repetitive exposure of GGBS to rats was tested over a period of 4 weeks with 6 h exposure per day for 5 days per week. Results and conclusion: Even at high doses, GGBS was inactive and did not induce clinically relevant phenotypic changes in rats compared to concomitant controls.Together with both the previous acute toxicity and the dose range finding study in rats, it was shown that the exposure to the tested GGBS was unable to induce any severe pathogenic responses.