Can secondhand smoke cause breast cancer?
Research is still being done to find out whether secondhand smoke may increase the risk of breast cancer. Both mainstream and secondhand smoke have about 20 chemicals that, in high concentrations, cause breast cancer in rodents. Chemicals in tobacco smoke reach breast tissue and are found in breast milk. Any link between secondhand smoke and breast cancer risk in human studies is a subject of debate, partly because breast cancer risk has not been shown to be increased in active smokers. One possible reason for this is that tobacco smoke may have different effects on breast cancer risk in smokers and in those who are exposed to secondhand smoke. A report from the California Environmental Protection Agency (Cal/EPA) in 2005 concluded that the evidence about secondhand smoke and breast cancer is “consistent with a causal association” in younger women. This means that the secondhand smoke acts as if it could be a cause of breast cancer in these women. The 2006 US Surgeon General’s report,
