The data showed that the three classes of chemical compounds were widely detectable in the study population, and that high exposure to certain chemicals was associated with early breast development. The strongest links were seen with phthalates and phytoestrogens, which were also among the highest exposures. One phenol, two phytoestrogens, and a subset of phthalates (those found in building products and plastic tubing) were associated with later puberty. However, the phthalates found in personal products such as lotion and shampoo, especially those with fragrance, were related to earlier breast and pubic hair development.

"We believe that there are certain periods of vulnerability in the development of the mammary gland, and exposure to these chemicals may influence breast cancer risk in adulthood," Dr. Wolff continued. "Dietary habits may also have an impact. Further study is needed to determine how strong the link is."

Consistent with previous studies, researchers also found that body-mass index (BMI) played a role in the onset of puberty. About a third of the girls were considered overweight, which is also an indicator of early breast development. As a result, some of the chemical associations differed in more or less obese girls. Researchers continue to study the impact of diet on pubertal development and eventual breast cancer risk.

"Exposure to these chemicals is extremely common," Dr. Wolff continued. "As such, while the association between chemicals and pubertal development seems small, the impact on the overall population is significant."

Source: The Mount Sinai Hospital / Mount Sinai School of Medicine