The World Health Organization’s International Agency for Research on Cancer announced October 17 that it will consider air pollution as a carcinogen. While individual risk is low, sources of the gases and particulate matter can be found in multiple sectors, including transportation and agriculture. The pollution, previously considered to increase the risk of heart and lung disease, has been identified as the highest priority environmental carcinogen, ahead of secondhand smoke. Following the report’s release, Senate Environment and Public Works Chairman Barbara Boxer (D-CA) announced that the committee would hold a hearing on air pollution.