The California Air Resources Board (CARB) evaluated formaldehyde exposure in California and found that one of the major sources of exposure is from inhalation of formaldehyde emitted from composite wood products containing urea-formaldehyde resins. Formaldehyde is a respiratory irritant. In addition, the International Agency for Research on Cancer (IARC) classifies formaldehyde as being "carcinogenic to humans" based on the increased risk of nasopharyngeal cancer. Formaldehyde was also designated as a toxic air contaminant (TAC) in California in 1992 with no safe level of exposure. State law requires CARB to take action to reduce human exposure to all TACs.