We’ve known for decades that tobacco increases the risk of lung cancer, as well as cancers of the mouth, lips, nose, throat, larynx, esophagus, stomach, pancreas, kidney, bladder, uterus, cervix, and colon. A growing body of evidence suggest breast cancer should be added to that list as well, with the most recent studies suggesting that women who start smoking at an early age have the greatest increased risk of being diagnosed with breast cancer, especially if they started smoking prior to giving birth. The risk may possibly be higher in women who become heavy smokers at a young age. And there’s science to support the connection. The International Agency for Research on Cancer has identified 20 known or suspected substances in tobacco smoke that can increase breast cancer risk, as well as biological mechanisms that explain how exposure to these carcinogens could lead to breast cancer.

Studies on secondhand smoke have had consistent findings. These studies found younger, premenopausal women who have never smoked but did have exposure to secondhand smoke have an increased breast cancer risk. Whether secondhand smoke is also linked to postmenopausal breast cancer is not yet clear.

In addition, studies have found women who smoke are at increased risk of having a breast cancer recurrence.

If you or someone you know smokes, it’s never too late to quit. SmokeFree.gov offers tips and support for quitting. And if you don’t smoke, spend as much time as you can in smoke-free environments. It will do a lot for your lungs–and it could decrease your risk of breast cancer too!