Early puberty is becoming the norm, not the exception. The Breast Cancer Fund commissioned a meta-analysis of existing data on this subject in order to explore research indicating that early menarche is a risk factor for later development of breast cancer. The resulting publication, The Falling Age of Puberty in U.S. Girls, was authored by Sandra Steingraber — best known for her work on the links between environmental toxins and cancer — traces the complex and interlocking relationships between puberty; physiological, psychological and environmental conditions; and the consequences for the maturation process of our young women.
Turning puberty on in America
It’s remarkable how little we know about puberty. While we understand the basic neural and hormonal pathways that interact to initiate the processes involved in puberty development — including development of breasts (thelarche) and pubic hair (pubarche), and first menstruation (menarche) – the process has no predetermined onset or length. Timing varies widely and can be influenced by a wide range of environmental factors and cues that are not entirely known. “Normal” puberty onset can range from ages 8-13 and takes, on average, 1.5-6 years to complete.
Good documentation exists from the last century or so to establish that the average age of first menstruation in White U.S. girls has declined by several years, from an average of 17 to 13 years of age. Over the last 50 years, the age of first menstruation continued to decline, but at a much slower rate (by a few months) and with wide ethnic disparity. White girls in the U.S. now menstruate at an average age of 12.6 years; African American girls at 12.1 years; and Latinas at 12.2 years. It’s not clear how far these differences can be traced, however, since most historical documentation focuses on White American and European girls.
There is also a dearth of information about changes in the earlier signs of pubertal development, such as the onset of breast budding. Data from the last few decades show a dramatic decline in the onset age for both breast budding and pubarche, and rates are continuing to decline. To put this into context, Steingraber says, “Girls get their first periods, on average, a few months earlier than girls 40 years ago, but they get their breasts one to two years earlier.”
In the U.S., 50% of White girls now show signs of breast budding before age 10, with as many as 14% showing breast development by age 8. The average age of breast budding for African American girls is just under 9 years, with a significant percentage of thelarche development before age 8. Steingraber concludes, “It is now the opinion of most endocrinologists…that the falling age of puberty among U.S. girls is a real and ongoing phenomenon.” It’s less clear why this is happening and what should be done about it.
Chemical cocktails and the new “normal”
Most experts agree that the decline in the age of puberty is attributable to decreased rates of disease, increased nutrition, and human females’ ability to adapt sexual maturation to environmental cues (e.g., health, food, shelter). This is why it is difficult to speak of a “normal” age and time for puberty. We are adaptive creatures and “normal” depends upon our personal and communal conditions. This also means that “normal” puberty development is not necessarily “good” or “healthy;” it’s simply an average marker of response to external circumstances that impact internal functions.
Steingraber argues that, particularly in the last several decades, these trends seem to be responding to stimuli beyond nutrition and general health. She highlights numerous studies linking exposure to environmental chemicals (particularly endocrine-disrupting chemicals, which can mimic hormones in the body) to health concerns such as shortened gestational periods in fetal development, low birth-weight babies, increased obesity, and poor insulin regulation.
This should make us sit up and take notice since, as Steingraber says, “children are exposed continuously to low-level endocrine disruptors in their diets, drinking water and air supply.” Chemical flame retardants (e.g., polybrominated biphenyls [PBBs]) have been linked to earlier menstruation and pubarche. Similarly, high levels of dioxin exposure have been associated with elevated risks for breast cancer and early menarche. Hormonally active components, which have been linked to earlier pubertal development, can be found in many products including hair tonics, pesticides, and building materials. Animal studies indicate that prenatal and early-life exposure to bisphenol A (originally developed as a synthetic hormone and now used in all polycarbonate plastics and food and beverage can lining) can induce earlier sexual maturity. Analysis of U.S. girls’ urine indicates the presence of hormonally active agents and traces of known human contaminants such as phthalates and bisphenol A.
Steingraber concludes that this chemical cocktail may be a significant factor in the “new normal” rates of girls’ pubertal development. There’s not enough research to say for sure — only enough to raise red flags. We need to know how these chemical contaminants combine with other known risks for early puberty development — smoking, obesity, physical inactivity, and psychosocial stressors — to contribute to early puberty onset, and what other physical consequences this may have for human development.
The loss of childhood
In addition to the increased risk for breast cancer and the effects of chemical contaminants on human development, there are also social reasons to be concerned about the declining age of puberty.
While one may argue that, as puberty declines, we may need to separate our notions of “childhood” from physiological development (an 8-year-old with breasts is no less a child than one who has yet to develop), society nevertheless projects a multitude of pressures on young girls who mature at an early age. Steingraber reports that girls who enter puberty earlier are more likely to report anxiety, negative self-images, suicidal ideation, substance abuse and cigarette smoking. Girls with early pubertal development are also more likely to be victims of physical and sexual violence. They have lower levels of academic achievement and a higher and earlier level of sexual activity, and are more likely to experience a teenage pregnancy. Early maturing boys do not have these behavioral patterns or outcomes. Steingraber comments, “It may be that “early puberty alters a girl’s social interactions in ways that produce trauma and erode self-esteem.”
What we need to do
Steingraber’s exhaustive analysis is a tribute to her ability to integrate biomedical knowledge with environmental and chemical research and social and cultural determinants and consequences. This is no simple endeavor.
Our lack of information about the chemicals in our environment and their consequences for human health is striking. We require a more holistic view of human bodies and our environmental surroundings. Steingraber suggests routinely screening for endocrine-disrupting chemicals and hormonally active agents in air, water, and food, and monitoring the effects these chemicals have on human development. We also need to study the potential damaging effects of chemicals on human and environmental health prior to their mass use in consumer and other products. Governments also need to better regulate the use and release of these chemicals into our environment.
Steingraber’s report effectively concludes that the trigger for girls’ early puberty development is an intermingling of factors that initiate multiple changes and set the stage for other responses. To unravel all of this, we need to begin to appreciate the interplay between our environment’s chemical burden and our bodies’ physical and social development. Our evolution may depend on it.
By Kathleen O’Grady
Kathleen O’Grady is the co-author of Sweet Secrets: Stories of Menstruation (Sumach Press) and a Research Associate at the Simone de Beauvoir Institute.
This article is abridged and adapted from “Early Puberty for Girls”, by Kathleen O’Grady, which originally appeared in the Canadian Women’s Health Network’s Network Magazine, Issue 11, No 1, Fall/Winter 2009. Available on-line at http://www.cwhn.ca/network-reseau/11-1/11-1pg4.html. It is reprinted by permission of the Canadian Women’s Health Network and Kathleen O’Grady.
The Falling Age of Puberty in US Girls: What We Know, What We Need to Know by Sandra Steingraber (Breast Cancer Fund, 2007)
State of Evidence: The Connection Between Breast Cancer and the Environment edited by Janet Gray (Breast Cancer Fund, 2008) www.breastcancerfund.org