The goal of the ELLA study is to learn more about how exposure to environmental chemicals during adolescence, a period of rapid growth and change, affects the developing body and how these changes might increase breast cancer risk later in life.

Studies suggest that the origins of breast cancer can occur early, for instance in the womb and during puberty. These time periods are commonly referred to as “windows of susceptibility”—key developmental stages when an individual may be most vulnerable to environmental exposures. We see evidence of this from many studies. For example, women who were exposed in the womb to DES (diethylstilbestrol), a synthetic estrogen given to pregnant women starting in the 1940s to reduce the risk of complications, have approximately twice the risk of developing breast cancer after the age of 40 as unexposed women. Similarly, women who were exposed to the highest levels of the pesticide DDT before the age of 14 were found to have a fivefold increased risk of developing breast cancer compared to women with lower exposures.

Environmental chemicals have been shown to contribute to a broad range of developmental and reproductive problems as well, and the health effects from early life exposures may not appear until years later. For instance, researchers found that children who were exposed in the womb and in early childhood to PBDEs, a widely-used class of flame retardant chemicals, had deficits in attention, cognition and fine motor skills at ages five and seven. Environmental exposures early in life have also been linked with obesity, diabetes, and a number of other disorders.

Adolescence represents an especially important window of susceptibility, since this a period during which breast cells are dividing rapidly and the mammary gland undergoes extensive changes. Despite that, few studies to date have focused on environmental exposures during puberty. The ELLA study is unique in that it is the first study to look at the influence of environmental chemicals on breast composition in adolescent girls. Studies in mice, conducted in parallel, will further elucidate the mechanisms underlying this relationship between chemicals and breast cancer risk.