Gallium arsenide (
GaAs) is an important
semiconductor material. In 2-year inhalation studies,
GaAs increased the incidence of lung
tumors in female rats, but not in male rats or male and female mice. Alveolar proteinosis followed by chronic active
inflammation was the predominant non-neoplastic pulmonary findings. IARC classified
GaAs as carcinogenic to humans (group 1) based on the assumption that As and Ga
ions are bioavailable. The European Chemical Agency Risk Assessment Committee concluded that
GaAs should be classified into Carcinogenicity Category 1B (presumed to have carcinogenic potential for humans; ECHA). We evaluate whether these classifications are justified. Physico-chemical properties of
GaAs particles and the degree of mechanical treatment are critical in this evaluation. The available data on mode of action (MOA), genotoxicity and bioavailability do not support the contribution of As or Ga
ions to the lung
tumors in female rats. Most toxicological studies utilized small particles produced by strong mechanical treatment, destroying the crystalline structure. The resulting amorphous
GaAs is not relevant to crystalline
GaAs at production and processing sites. The likely tumorigenic MOA is lung toxicity related to particulate-induced
inflammation and increased proliferation. It is concluded that there is no evidence for a primary carcinogenic effect of
GaAs.