Breast Cancer Risk Factors
At a Glance
These factors can increase or decrease breast cancer risk. The protective factors can actually reduce breast cancer risk.
Factors that influence breast cancer risk include:
- Lifestyle factors like diet and exercise
- Systemic factors like race, power, and inequities
- Chemical and radiation exposures (see our Glossary of Exposures for more)
- Genetics
See pullouts from Paths to Prevention: the California Breast Cancer Primary Prevention Plan for the science on each breast cancer risk factor.
Chemicals in Consumer Products
- Starting in utero, we are exposed to harmful chemicals from consumer products
Diet and Nutrition
- Healthy dietary patterns may be protective against breast cancer.
Genetics
- 5-10% of breast cancers are attributed to genetic history
Ionizing Radiation
- Medical diagnostic procedures such as CT scans and X-rays
Light at Night
- Nightshift work is a probable human carcinogen
Non-Ionizing Radiation
- Cell phone evidence mixed
- Risk from electric power transmission line close proximity
Occupation
- Chronic chemical exposure in the workplace
Pharmaceutical Hormones
- Some Hormone replacement therapy (HRT) treatments are known carcinogens
Lack of Physical Activity
- Physical activity is protective against breast cancer
Place-based Chemical Exposures
- Highway pollution, industrial facilities, and trash disposal sites
Pregnancy-related Factors
- Age, number of births, and breastfeeding can all impact risk

Types: Article, Fact Sheet, Link, Report