November 24, 2003
Ms. Barbara Brenner
Executive Director
Breast Cancer Action
55 New Montgomery Street, Suite 323
San Francisco, CA 94105
Dear Ms. Brenner:
Your advertisement, “The Cosmetics Industry and Breast Cancer, Philanthropy or Hypocrisy,” published in The New York Times on October 24, makes the statement that “because phthalates are also endocrine disruptors, concerns have been raised as well about their association with breast cancer.” Your web site also refers to phthalates as “hormone mimicking” compounds.
These allegations are not correct in the context of the cause you champion. It is a generally accepted conclusion of the scientific community that phthalates do not act as estrogenic compounds in living organisms; they neither mimic the effect of estrogen nor interfere with its function. The misconception stems from some research in the early ‘90s, which seemed to indicate that phthalates could impact the function of estrogen in in-vitro (test tube) experiments.
However, phthalates are converted to by-products before they enter the blood stream, and it has been demonstrated that these by-products do not impact the function of estrogen.1,2 In 1998, research demonstrated that phthalates do not induce estrogen-like effects in living organisms. 3 And in 2000, additional research demonstrated that the early in-vitro studies were not relevant to what happens in live organisms. 4,5 Specifically, Parks concluded that: “none of the phthalates that are active in vitro display such estrogenic activity in vivo.” Other animal studies have shown that phthalates do not influence other hormone-driven effects, such as sexual maturation.
Additional reassurance about phthalates can be derived from the Centers for Disease Control and Prevention (CDC) Second National Report on exposure to environmental chemicals. This report shows that general population phthalate exposures are well below safety levels set by the Environmental Protection Agency, even at the 95th percentile levels. Exposure tables are attached for your information.
We provide this information in the spirit of your commitment to science and balanced communications as expressed on your web site. If you would like to pursue any phthalate matter further, you will find the Phthalate Esters Panel and its Toxicology Research Task Group open to address the Panel’s understanding of the science. In the more than 50 years of use, phthalates have been very extensively studied. Consequently, we are confident that we can address any concerns your organization may have about phthalates in its efforts to identify possible causes of breast cancer.
Very truly yours,
Marian K. Stanley
Senior Director, CHEMSTAR
Manager, Phthalate Esters Panel
References
1 Harris, C., Henttu, P., Parker, M., and Sumpter, J. (1997). The estrogenic activity of phthalate esters in vitro. Environmental Health Perspectives 105: 802-811.
2 Picard, K., Lhuguenot, J.-C., Lavier-Canivenc, M.-C., and Chagnon, M. -C. (2001). Estrogenic activity and metabolism of N-butyl benzyl phthalate in vitro: Identification of the active molecules. Toxicology and Applied Pharmacology 172: 108-111.
3 Zacharewski, T., Meek, M., Clemons, J., Wu, Z., Fielden, and Matthews, J. (1998). Examination of the in vitro and in vivo estrogenic activities of eight commercial phthalate esters. Toxicological Sciences 46: 282-293.
4 Moore, N. (2000). The oestrogenic potential of the phthalate esters. Reproductive Toxicology 14: 183-192.
5 Parks, L., Ostby, J., Lambright, C., Abbott, B., Klinefelter, G., Barlow, N., and Gray, L. (2000). The plasticizer diethylhexyl phthalate induces malformations by decreasing fetal testosterone synthesis during sexual differentiation in the male rat. Toxicological Sciences 58: 339-349.