Factors inside and outside our bodies affect our health. Those outside our bodies are often called environmental factors.
There is no one scientific definition for the term “environment.” In health research, different scientists may use different categories when deciding whether a risk factor is environmental.
Environmental factors may include things found in nature that we eat, drink, touch or breathe, as well as man-made factors. Examples may include exposures that are passive (such as sunlight or secondhand smoke) and those that are active (such as eating fruits and vegetables or drinking alcohol).
Even medications, such as birth control pills or menopausal hormone therapy (postmenopausal hormones), are sometimes considered environmental exposures.
Factors such as age, the hormones produced in our bodies (such as estrogen) and family history are considered to be personal or genetic factors rather than environmental factors. However, they can interact with environmental factors and affect our health.
Some factors in our environment help keep us healthy. Others can increase our risk of breast cancer or other diseases. Still others have little, if any, effect on our health.
Researchers can use different types of studies to learn about the environment and breast cancer risk (learn more).
To learn more about the role of the environment in breast cancer, Komen sponsored a study from the Institute of Medicine (IOM), "Breast Cancer and the Environment, a Life Course Approach."
A culturally appropriate, related Question and Answer booklet on breast cancer and the environment is also available in Spanish.
The IOM reviewed the scientific evidence on environmental factors and concluded:
Environmental factors with consistent evidence showing a link with an increased risk of breast cancer were:
An environmental factor with consistent evidence showing a link with a decreased risk of breast cancer was:
Environmental factors with consistent evidence showing no link with breast cancer risk were:
The IOM also identified future needs for breast cancer research on environmental factors including:
Building on this groundbreaking work with the IOM, Komen offered the Environmental Challenge grants in fiscal year 2013 to better understand the role that the environment may play in breast cancer development.
The five grants include separate studies into:
Learn more about Komen research programs.