One of our ongoing concerns here at esnl has been the flooding of the environment of daily living with a host of chemicals about which we known comparatively little.
First, these chemicals used in our foods, clothing, and cosmetics, and our our lawns, furniture, and cookware [to name just a few of their applications] have received little testing, and virtually known in the way they interact with each other both within and without that complex ecosystem that is the human body. [Consider, for instance, the growing knowledge about the role the microbes dwelling within out guts may directly impact our moods.]
A special concern has been with the class of chemicals that mimic the actions of the endocrine system, that network of glands performing key roles in regulating the mechanisms of both body and mind.
Today’s post focuses on new revelations about two groups of endocrine-disrupting compounds.
Parabens linked to breast cancer
Parabens, short for parahydroxybenzoates, are chemicals widely used as preservatives in cosmetics, including sunscreens and shampoos.
But there’s a problem.
Parabens, you see, mimic the action of estrogen, and that’s particularly bad news for women, because parabens have now been conclusively linked to increased risk of breast cancer.
The chemicals had long been suspected of a role in breast cancer, as Medscape reported three years ago:
[R]esearchers in the United Kingdom examined 160 breast-tissue samples obtained from 40 patients who had undergone a mastectomy for primary breast cancer. They found that 99% of samples had traces of at least 1 paraben, and that 60% had traces of 5 different parabens.
Importantly, 7 of the women reported never having used underarm products. This suggests that the parabens originated from another source, note the authors.
The source of the parabens measured in this and in previous studies cannot be identified; it is also not clear if the paraben traces come from long-term accumulation, current exposure, or a combination of both.
But the link has grown much stronger, as Robert Sanders of the UC Berkeley News Center reports:
“Although parabens are known to mimic the growth effects of estrogens on breast cancer cells, some consider their effect too weak to cause harm,” said lead investigator Dale Leitman, a gynecologist and molecular biologist at UC Berkeley and an adjunct associate professor of nutritional sciences and toxicology. “But this might not be true when parabens are combined with other agents that regulate cell growth.”
Existing chemical safety tests, which measure the effects of chemicals on human cells, look only at parabens in isolation, he said. They fail to take into account that parabens could interact with other types of signaling molecules in the cells to increase breast cancer risk.
To better reflect what goes on in real life, Leitman and his colleagues looked at breast cancer cells expressing two types of receptors: estrogen receptors and HER2. Approximately 25 percent of breast cancers produce an abundance of HER2, or human epidermal growth factor receptor 2. HER2-positive tumors tend to grow and spread more aggressively than other types of breast cancer.
The researchers activated the HER2 receptors in breast cancer cells with a growth factor called heregulin that is naturally made in breast cells, while exposing the cells to parabens. Not only did the parabens trigger the estrogen receptors by turning on genes that caused the cells to proliferate, the effect was significant. The parabens in the HER2-activated cells were able to stimulate breast cancer cell growth at concentrations 100 times lower than in cells that were deprived of heregulin.
The study demonstrates that parabens may be more potent at lower doses than previous studies have suggested, which may spur scientists and regulators to rethink the potential impacts of parabens on the development of breast cancer, particularly on HER2 and estrogen receptor positive breast cells.
The findings also raises questions about current safety testing methods that may not predict the true potency of parabens and their effects on human health.
“While this study focused on parabens, it’s also possible that the potency of other estrogen mimics have been underestimated by current testing approaches,” said co-author Chris Vulpe, a toxicologist formerly at UC Berkeley but now at the Center for Environmental and Human Toxicology at the University of Florida College of Veterinary Medicine.
Their study is posted online here [PDF]
Triphenyl phosphates, or is your nail polish making you fat?
Another widely used endocrine disruptor has also become the focus on new concern, as Treehugger reports:
A compound used as a plasticizer and furniture fire retardant, triphenyl phosphate (TPHP), which has been linked to hormone and reproductive irregularities, obesity, and other health issues, is also found in some nail polishes. And while painted nails may not seem like an easy pathway to exposure for potentially toxic chemicals (as opposed to ingesting or inhaling the substances), a recent study from researchers at Duke University and the Environmental Working Group (EWG) indicates otherwise, and suggests that TPHP directly enters the body during and after the polish is applied.
TPHP has been used as a replacement fire retardant compound in furniture, especially foams, following the phaseout of the previous generation of fire retardant compounds, the polybrominated diphenyl ether (PBDE) group. However, recent studies have found troubling links to increased health risks, especially hormone-related issues, with exposure to TPHP as well, and because it’s an ingredient in a common beauty product, nail polish, and is not always disclosed on the label, painting your nails with certain brands of polish can carry a health risk with it.
The new study, Nailed, conducted by Dr. Johanna Congleton, a senior scientist at EWG, and Dr. Heather Stapleton, associate professor at Duke University, first tested 10 nail polishes for the existence of TPHP, none of which disclosed the chemical on their labels, and found it in 8 out of the 10. EWG has a listing of more than 3,000 nail polishes and treatments in its Skin Deep database, of which 49% list TPHP on their ingredients, but this recent finding of undisclosed TPHP in polishes suggests that it may be in more personal care products than was originally thought.
So next time you hear corporations and their scientific front men [yes, they are usually males] proclaim the safety of their latest nostrum, bear in mind all their other past proclamations about the safety of cigarets, leaded gasoline, DDT. . .well, you get the idea.