When a little girl starts growing breasts a year after losing her first baby tooth, her parents probably understand the situation as little as she does. And when it happens to girls across the country, and to many girls growing up in certain neighborhoods but not others, scientists struggle to explain the phenomenon as well.
Women's bodies have always carried biological freight from one generation to the next, bearing the physical imprint of industry and environmental loss. One of the most confounding effects of environmental change is precocious puberty among girls -- taking the form of an unusually young first period, early growth of pubic hair, or breast buds in the first grade -- which may be tied to where families live, the products they consume, and how healthy and happy they'll be later in life.
Various studies have suggested that the process of puberty may be influenced by exposure to a particular class of chemicals, known as endocrine disruptors, found in everyday products like water bottles, food packaging and cosmetics.
Chemistry No One Can Avoid
Endocrine disruptors change our body chemistry by altering the function of hormones, which dictate the way our bodies develop and behave. While many questions have arisen about the potential threats these chemicals pose to our health, numerous human and animal studies in recent years suggest significant, but often invidious, effects on growth, reproductive development, and, over time, risk of cancers and other diseases. An endocrine disuptor might "mimic" a pregnant woman’s natural estrogen and change the way the fetus develops, for instance. Or her shampoo could expose her every day to a chemical linked to aggressive or disruptive behavior in young children.
According to a review of environmental research by the Breast Cancer Fund, study after study has identified alarming twists in hormonal and child development -- including disruptions in puberty and elevated cancer risk in some cases -- that are tied to chemicals in cosmetics, building materials, detergents, vehicle exhaust and even baby formula packaging.
Whatever the health effects, no community can escape exposure to endocrine disruptors in a modern habitat, where toxins constantly mesh with the way we eat, work and play. Meanwhile, new research shows that the "body burden" of industrial chemicals also reflects and exacerbates divides of race, class and gender. Not only are endocrine disruptors increasingly pervasive among American women and girls; the consequences of this contamination tie into race and socioeconomic circumstance in ways we're just beginning to understand.
Last year, a group of researchers published findings of a study involving more than 1,200 girls, about six to nine years old, which showed that black and Latina girls displayed signs of puberty at a younger age than white peers, some developing breasts as young as seven years old. In an examination of related data on chemical exposures, the group also found that "Hormonally active environmental agents" had "small associations with pubertal development."
The findings reaffirmed previous studies that point to a nexus of puberty, race and chemicals in children's bodies. While scientists stress such findings are inconclusive, the mounting evidence of the chemical connection could illuminate a hidden dimension to environmental injustice in communities of color.
According to a 2007 report by the Breast Cancer Fund, the age range of puberty has been declining for American girls in general, but the patterns differ by race. The age of the first period for black girls has consistently been slightly younger than that for whites, the report stated, and "over the course of the 20th century, age at menarche fell faster and farther for U.S. black girls than for U.S. white girls." There has been a similar downward shift over the past 40 years for Mexican American girls. Other studies on girls in Europe did not indicate parallel trends.
Early onset puberty concerns health and community advocates because it ties into risks in every aspect of a girl's life. Psychologically, premature adolescence may be marked by confusion, depression, unwanted sexual advances and starting to have sex before many of their peers do. Medically, early puberty is associated with various health risks, including obesity and breast cancer -- issues that disproportionately impact black women.
The study published last year, which focused on girls in New York City, Cincinnati and Northern California, showed even more pronounced differences than seen in earlier studies: at age seven, nearly one in four black girls and nearly one in seven Latina girls showed breast growth, compared to only one in ten white girls. A year later at age eight, the rates of black and Latina breast development were 43 percent and 31 percent, respectively, but only 18 percent in whites. Another key set of findings by the research team, published in Environmental Health Perspectives by lead author Dr. Mary Wolff, revealed several small but notable correlations between some endocrine disruptors, particularly common phthalates, phenols and phytoestrogens, and unusual pubertal development.
Other research points to the effects of endocrine disruptors throughout a woman or child's life cycle. In a New York City-based study at the Columbia University's Children's Center for Environmental Health, which tracked pregnant Dominican and African-American women over several weeks, "Phthalates were detected in 85 [to] 100% of air and urine samples."
Sandra Steingraber, author of the Breast Cancer Fund report and a forthcoming book about toxins and environmental health, told On The Issues Magazine that her research on puberty patterns led her to conclude, "It was appropriate to see early puberty as a kind of ecological disorder, meaning that there are many contributing factors, not just any one."