Childhood and Adolescence
Research shows that childhood and adolescent exposures to medical radiation and chemicals like the pesticide DDT are linked to higher rates of breast cancer. Early puberty puts girls at a higher risk for later-life breast cancer.
Today, girls are entering puberty earlier than a generation ago — in part due to childhood exposures to endocrine disruptors (substances that can alter the body’s hormonal responses).
Girls get their first periods today, on average, a few months earlier than girls did 40 years ago, and they develop breasts one to two years earlier (Steingraber, 2007). This trend may be due to exposures to endocrine-disrupting compounds such as bisphenol A (BPA) and phthalates (Aksglaede, 2006; Steingraber, 2007) before puberty, when the reproductive system, including breast tissue, is extremely sensitive to low levels of estrogens (Aksglaede, 2006). The younger girls are when they enter puberty, the greater their risk of breast cancer later in life.
Evidence suggests that breast development is sensitive to other chemical exposures as well. A 2007 study illustrated that childhood and early adolescent exposures to the now banned pesticide DDT were associated with a fivefold increase in breast cancer before age 50 (Cohn, 2007). This is a particularly powerful study for two reasons. First, although researchers often have to rely on people’s best guesses about what they were exposed to earlier in life, in this case, scientists had access to blood samples taken during adolescence, allowing for actual measurements of DDT exposure. Second, since DDT was banned in 1972, scientists could study effects on health before and after the ban and distinguish effects on women dependent on their age during the period of peak use of DDT.
Research on childhood and adolescent exposures to ionizing radiation illustrates a similar effect. Women in Hiroshima and Nagasaki who were under 20 when the United States dropped the atomic bombs had higher rates of breast cancer than older women (Land, 1995; Pukkala, 1997). Similarly, young women exposed to massive amounts of radiation from the 1986 Chernobyl nuclear reactor accident are experiencing higher rates of breast cancer (Pukkala, 2006). It is too early to assess the late-life effects on women who were girls or teens at the time of the accident.
Girls who received repeated X-rays for scoliosis, and adolescent and very young women who received radiation treatment for Hodgkin’s and non-Hodgkin’s lymphoma, experienced higher rates of breast cancer than women who were older at the time of their X-rays or radiation treatment (Schellong, 1998; Clemons, 2000; Tward, 2006; Howe, 1996). Their rates were also elevated relative to their peers who did not receive medical radiation.