[Pharmwaste] Prenatal Origins of Endocrine Disruption - timeline
dldebiasi at deq.virginia.gov
Tue Feb 10 14:26:11 EST 2009
Prenatal Origins of Endocrine Disruption
Critical Windows of Development is a timeline of how the human body develops in the womb, with animal research showing when low-dose exposure to endocrine disrupting chemicals during development results in altered health outcomes.
A new window into hormone-altering chemicals
A new interactive database, including a timeline showing how human fetuses develop, displays scientific data about controversial chemicals in a graphic way.
By Marla Cone
Editor in Chief
Environmental Health News
February 9, 2009
An electronic database going public on Tuesday (2/10/09) has gathered the latest science on some of the most controversial chemicals in use today, offering a handy look into potential health effects when babies are exposed while developing in the womb.
The interactive website, called "Critical Windows of Development," has compiled an array of data from hundreds of scientists studying low doses of endocrine-disrupting chemicals.
Theo Colborn, a scientist often credited with discovering in the early 1990s that environmental pollutants were mimicking and altering hormones, led the effort to create the database. She said her intent is to give scientists, policymakers, journalists and others immediate access to the information in a user-friendly, visually interesting way.
"This puts information directly at our fingertips with the utmost ease," said Gail Prins, a physiology professor at University of Illinois at Chicago and one of a few dozen scientists who have previewed the website.
"By making it electronic, the worldwide availability is a tremendous step forward in data dissemination," Prins said.
The website compiles information from hundreds of studies and inserts it on timelines that show the development of key bodily systems in both people and animals, including the male and female reproductive tracts, immune system and nervous system.
By layering research results over these timelines, Colborn provides graphic evidence that there is a large body of animal research suggesting that low doses of chemicals might be harming human fetuses.
When a Critical Windows user chooses a chemical, red lines appear on a timeline, displaying the areas of development where effects have been found in laboratory animals exposed to low doses. Clicking on a triangle retrieves a summary of each study, which then leads to direct access to the published article in a scientific journal.
So far, information is displayed for bisphenol A, dioxin and phthalates. Dozens, perhaps hundreds, of industrial chemicals and pesticides in use today can disrupt hormones, but two of them--BPA, found in hard plastic, and phthalates, used in cosmetics and vinyl--are among the most controversial.
The new database "pairs normal human development in the womb with laboratory research showing where and when low-dose exposure to bisphenol-A, phthalates and dioxin has effects," wrote Colborn, founder and president of The Endocrine Disruption Exchange, a nonprofit organization, and Carol Kwiatkowski, its director.
Some scientists said they will use the new database at upcoming public meetings where decisions are being made about regulating chemicals.
On Tuesday, Prins plans to display the website on a screen in front of the Chicago City Council as the politicians debate an ordinance that would ban BPA in plastic baby products.
"It's not just an academic exercise," said Prins, who studies how neonatal exposure to estrogens affects the prostate. "The uniformed person can make a visualization and get a grasp of what information is out there."
Next month, John G. Vandenbergh, Professor Emeritus in at North Carolina State University's Department of Biology, said he will use it at a workshop in Berlin held by Germany's environmental agency to discuss the possible human risks of BPA exposure.
Vandenbergh said it will be "useful to call up references to bolster or refute items as they arise."
Before Critical Windows, Prins said she and other scientists "had to do so much digging around" to find data. "Literature searches can really bog one down. It is painstaking. It would take us hours, weeks," she said.
For example, she recently needed to know whether exposure to BPA affected immune systems in animals. She had to search and cross-search medical literature websites. Now, with the new database, she can find the same information with a few clicks of a mouse.
Vandenbergh said one of the most important benefits is that the new timeline will help scientists instantly identify where more research is needed. "For example, I was especially surprised to see the gaps in the phthalate data," said Vandenbergh, whose research focuses on how prenatal exposure to hormones disrupts rodent physiology and behavior.
Colborn and Kwiatkowski said they created the timeline because of the "widespread and unavoidable presence of endocrine disrupting chemicals in our lives."
Many human diseases, including asthma, autism, prostate cancer and breast cancer, are reaching record numbers, while animal research has shown that exposure to certain chemicals in the womb might lead to disease by skewing development of the brain, reproductive tract and other systems.
Critical Windows focuses on fetal development because it is the most vulnerable time for damage from hormones or hormone mimics.
For example, clicking on a triangle early in the timeline shows that rats had decreased sperm count when exposed to phthalates during the first few days of gestation. Clicking on a BPA triangle showed that pre-cancerous growths were found in the prostates of mice exposed a few days after birth, a period comparable to five or six months of pregnancy for humans. For dioxin, exposure on the eighth day led to decreased brain weight in rats.
Each summary describes the animals tested, the doses used, how the chemical was administered and how it corresponds to human gestation.
The website lines up the 38 weeks of human gestation with the 41-day development period of lab rats and mice. That allows scientists and others see how each animal tests might be relevant to pregnant women.
Vandenbergh said the site is "quite user friendly" and will be helpful to those making human risk decisions. He added that it will have limited appeal to the general public, although it will be useful for teachers and professors.
The timeline only includes studies of animals exposed to one part per million or less, amounts that people may encounter in the environment or in consumer products.
All studies included on the timeline have been peer-reviewed and published; in addition, The Endocrine Disruption Exchange subjected the studies to its own review by 40 scientists before inserting them on the timeline.
"It is important to note that we did not interpret the research. We simply cataloged the information to present it to the public," Colborn and Kwiatkowskit said on their website.
Research that found no effects is not included on the timeline, although the website includes such studies on a separate list.
The lack of so-called "negative" studies does not bother Prins.
"The timeline is introduced as a reference database for studies that have shown effects. It does not bill itself as a database for all studies. So in that respect it is honest and not misleading," she said. "On the other hand, it would be nice if the government or Food and Drug Administration had a similar database site that presented all positive and negative findings"
Vandenbergh said he recommends omitting one statement on the site that says "you are exposed to hundreds of chemicals every day."
"This implies that all 'chemicals' are bad and that is just not true. Many are very beneficial, he said.
Prins said she "spent an hour or two just playing with it, looking at all the information" and concluded that Colborn and her colleagues "are trying to make it as comprehensive and complete as possible."
The one major shortcoming, Vandenbergh and Prins said, is they want data on more chemicals, including polychlorinated biphenyls, pesticides, soy products and arsenic.
The group spent years compiling the data for Critical Windows, which was funded by private foundations. Colborn said one of the most important features is that it can be updated as often as necessary. She said new studies are continously being added when they are published, and she hopes to expand it to new chemicals in the future.
Colborn is a professor emeritus of zoology at the University of Florida. In the late 1980s and early 1990s, she was a scientist at the World Wildlife Fund, where she noticed that various scientists were finding evidence that chemicals in the environment could act like hormones and skew animals' development.
Deborah L. DeBiasi
Email: dldebiasi at deq.virginia.gov
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