A study published by the Canadian Center of Occupational Health and Safety also found that Titanium Dioxide has been classified as "possibly carcinogenic to humans" by the International Agency for Research on Cancer (IARC). The IARC study found that "high concentrations of pigment-grade (powdered) and ultrafine titanium dioxide dust caused respiratory tract cancer in rats exposed by inhalation and intratracheal instillation." However, this link was discovered after high dose exposure to rats in conditions unlike those found when using Titanium Dioxide as a topical ingredient; it is, however, a potential indicator for the effects of Titanium Dioxide when used in occupational situations.