Teenage years are also a time of rapid growth. Girls' bodies begin producing higher levels of estrogen and progesterone, their reproductive tract undergoes change to prepare for pregnancy and their breasts go through rapid development. All of these changes make their bodies vulnerable to environmental contaminants.

• Teens often begin using makeup and personal care product , many of which contain ingredients that may be harmful to their health. While the chemicals present in any one cosmetic product alone may not cause harm, teenagers, like adults, use on average more than 10 personal-care products every day.

• Each day, nearly 6,000 children under 18 years of age start smoking, and 2,000 of them will become regular smokers. Approximately 90 percent of smokers begin smoking before age 21. Studies indicate that when multiple factors are taken into account, such as the length of time a person has been a smoker and the amount she or he smokes, smoking during adolescence causes more damage than at other times, especially increasing the risk for lung cancer. Secondhand smoke may also increase risk for breast cancer, and developing breast tissue may be quite sensitive to environmental contaminants.

Resources

Breast Cancer Fund's The Falling Age of Puberty in the U.S. report

Breast Cancer Fund’s Cosmetics Popular with Teenagers Linked to Breast Cancer, Other Serious Health Problems factsheet