The scientists in the new review said neither of those applies to hormone-like chemicals.
"Accepting these phenomena should lead to paradigm shifts in toxicological studies, and will likely also have lasting effects on regulatory science," they wrote.
In the report, the scientists were concerned that government has determined "safe" levels for "a significant number of endocrine-disrupting compounds" that have never been tested at low levels. They urged "greatly expanded and generalized safety testing."
"We suggest setting the lowest dose in the experiment below the range of human exposures, if such a dose is known," they wrote.
Vandenberg said that there may be no effect or a totally different effect at a high dose of a hormonal substance, while a lower dose may trigger a disease.
The breast cancer drug tamoxifen "provides an excellent example for how high-dose testing cannot be used to predict the effects of low doses," according to the report. At low doses, it stimulates breast cancer growth. At higher ones, it inhibits it.
"Imagine taking 100 individuals that are representative of the American population and lining them up in order of exposure to an EDC [endocrine-disrupting compound] so that the person on the far left has the least exposure and the person on the far right has the most. For many toxic chemicals, individuals with the highest levels of exposure, at the right end of the line, have the highest incidence of disease. But for some EDCs, studies suggest that people in the middle of the line have the highest risk," Vandenberg said.
She compared hormones, which bind to receptors in the body to trigger functions such as growth of the brain or reproductive organs, to keys in a lock.
"The more keys that are in the locks, the more of an effect that is seen. But at some point, the locks are overwhelmed and stop responding to the keys. Thus, in the lower range, more keys equals more of an effect, but in the higher range, more keys equals less of an effect," she said.
Vandenberg predicted the report "will start conversations among academic, regulatory and industry scientists about how risk assessments for EDCs can be improved."
"The question is no longer whether these phenomena exist, but how to move forward and deal with them."
This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.