In 2000, the National Institute of Environmental Health Sciences' National Toxicology Program published its 9th Report on Carcinogens, which included secondhand smoke on its list of known human carcinogens for the first time.
In 2002, the National Toxicology Program issued the updated 10th Report on Carcinogens, which reconfirmed that secondhand smoke is a known human carcinogen, based on studies showing a causal relationship between secondhand smoke exposure and lung cancer, nasal sinus cancer, and other cancers.
In 2005, the National Toxicology Program issued its 11th Report on Carcinogens. The report contained a six-page section on tobacco and secondhand smoke, which again confirmed that secondhand smoke is a known human carcinogen.
The 14th Report on Carcinogens, released on November 3, 2016, likewise contained a section on the hazards of secondhand smoke exposure.