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During human development, there are critical periods of susceptibility when mammary development, dependent on hormonal activity, may be particularly vulnerable to the effects of chemical pollutants. 

Changes in natural bodily hormone levels during pregnancy can dramatically impact the fetus, which is undergoing an intense period of growth. As early as the 1930s, lab experiments demonstrated that pregnant rats given an extra dose of estrogen, either natural or synthetic, gave birth to offspring that had defects in sexual development. In the females, such defects took the form of structural defects of the uterus, vagina, and ovaries; and, in males, stunted penises and other genital deformities.(15) Both epidemiological and lab studies done more recently demonstrate that mammary cells are susceptible to the carcinogenic effects of pollutants and hormones during early stages of development and can result in increased incidence of breast cancer.(16-20)

In 1938, the man-made hormone, diethylstilbestrol (DES), became the first manufactured estrogen prescribed for women. For the next several decades, DES was given to pregnant women who were at risk for miscarriage, the thought being that miscarriages were a result of lower levels of estrogen. While the babies born to women prescribed this drug appeared perfectly healthy at birth, they had ticking time bombs in their newborn bodies because of their early DES exposure. As they entered adulthood in the 1960s and 70s, it was discovered that they had increased risk of some types of rare cancer, reproductive tract structural differences, pregnancy complications, and infertility. Lab studies also suggest that fetal exposure to DES may be associated with an increased risk of breast cancer.(21) 

The tragedy of DES and other studies illustrate some important lessons:

• Prenatal exposure to chemicals can result in health effects later in life.
• Excessive amounts of estrogen prenatally can lead to reproductive health effects later in life, including breast cancer.
• Synthetic, man-made chemicals can fool the body and mimic the natural work of its hormones.
• The presence of one reproductive disorder may signal the presence of others.

Historically, it was thought that the placenta protected the fetus, but unfortunately we now know that fetuses are exposed to the chemical pollutants their mothers are exposed to. In a study that analyzed the umbilical cord blood of 10 randomly selected newborns, an average of 200 chemicals were detected; of the chemicals found, 180 are known to cause cancer in humans or animals.(22) 

Health effects from fetal exposure to chemical pollutants are relatively easy to track since the fetus is in a contained environment for a limited period of time. It is more difficult to track the many chemical exposures a growing child may encounter that can lead to health effects, including breast cancer, later in life. Nevertheless, periods of rapid growth and development continue throughout childhood, and children continue to be exposed to chemicals in their environment, even through some of their toys and other childcare products. Children, because of their anatomies and behavior, take in more of these substances pound per pound, than adults.

Examples of endocrine-disrupting compounds to which children are typically exposed include —

• Bisphenol A (BPA) — a synthetic estrogen that is used in some food and beverage containers (including baby bottles and some “sippy” cups) which can leach into foods and liquids
• Pesticides ingested through food and beverages and potentially encountered if used in the home or outside.
• Phthalates — an additive found in toys and some body care products.
• Dioxins — a by-product of PVC manufacturing and incineration, found in meat, fish, or milk.
• Flame retardants — found in many consumer products such as mattresses and pajamas (23)
• Recombinant bovine growth hormone (rBGH/rBST) — a synthetic hormone given to cows to increase milk production which is found in milk products.

As noted earlier, adolescence is a period when breast cells experience rapid hormone-driven growth and are at increased risk for cancer if exposed to excessive estrogen and/or toxins, therefore, immature breast cells are more likely to be damaged by exposure to environmental chemicals. Additionally, until a woman’s first full-term pregnancy, her breast cells are not fully mature and are particularly vulnerable to the effects of carcinogens.(9, 24) While current research is limited, scientists are concerned about the effects of exposure to EDs on adolescents. One recent study showed that exposure to DDT (an endocrine disrupter) during childhood or early adolescence increased the risk of breast cancer after age 50 by five times.(25)

There are specific behaviors and life-style factors that come into play during adolescence that may increase potential exposures and an adolescent’s risk of developing breast cancer later in life. These include —

• Increased use of cosmetics and personal care items, many of which contain EDs.(26)
• Alcohol consumption.(27, 28)
  
• Oral contraceptives. Some studies have reported a slight increase in breast cancer risk associated with teen use of oral contraceptives, as the use of oral contraceptives adds to a woman’s lifetime estrogen load.(28)
  
• Smoking. Cigarette smoke contains carcinogenic chemicals.(28)
• Increased consumption of fatty foodssuch as pizza and hamburgers — some studies have shown a link between consumption of dietary fat and breast cancer, though findings are mixed.(29)

breast cancer, susceptibility, life-style, behavior, chemicals, critical period

Last updated 387 days ago by Katie Huffling