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 Web site 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 Web site.
Research that found no effects is not included on the timeline, although the Web site 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.