Dramatically early breast development in Puerto Rican girls has been a long-standing mystery in public health. First noted two decades ago (Pérez 1982, Bongiovanni 1983), no explanation has ever been confirmed. Girls in Puerto suffer from the highest rate of " premature thelarche" ever recorded.

Colon et al. provide data linking this public health anomaly to phthalate exposure. The link does not prove causation, but is sufficiently strong to warrant urgent study. Can causation be established, and where does the phthalate exposure originate?

What did they do?
Colon et al. measured the presence of certain phthalates in the blood of 41 girls experiencing early breast development and a matched set of controls. The average age of girls with premature thelarche was 31 months.

What did they find?
They found high phthalate levels in the girls suffering from premature thelarche compared to the controls. The most dramatic difference they found was for DEHP, a known anti-androgen. Average for cases was 450 parts per billion vs. an average of controls of 70 ppb. In other words, girls with premature thelarche had DEHP concentrations almost 7 times that of the control group. This result was statistically significant.

Not all cases of premature thelarche in the study sample contained elevated levels of DEHP.

What does this mean?
"The present study provides the first analytical evidence of the presence of plastic additives with known estrogenic activity in girls with premature thelarche. In a study conducted in 1997 that included 17,077 girls, Herman-Giddens et al. reported that girls in the United States are developing pubertal characteristics at younger ages than previously reported. These authors concluded that the possibility that the increasing use of certain plastics and insecticides that degrade into substances that have estrogen-related physiological effects on living things should be investigated in relation to the earliest onset of puberty."

Shortly after the publication of this study, the CDC reported widespread phthalate contamination among adult Americans, but with no companion data on health impacts. The current study (Colon et al.) documents phthalate contamination in a pattern that suggests health impacts. It is restricted geographically to Puerto Rico, and deals with an age cohort different from the CDC's focus. Taken together, these two studies raise very large red flags for the debate about phthalate safety.

Colón et al. are very careful to point out that their study does not prove causation.

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