The absence of controlled trials on humans is the biggest missing link in environmental chemicals research.
The proof-of-concept Stealth Syndrome Study supported by CRECH will be the first because it pioneered a protocol to overcome the ethical issues.
No previous trials have been conducted because it is unethical to deliberately expose humans to chemicals suspected of being harmful. This is why rats and mice (murine model) are commonly used.
However, research conducted on a murine model is no guarantee that the same effects will be seen in humans. This disconnect is often cited as one of the main reasons why the majority of new pharmaceuticals which have shown promise in the lab (murine) fail in trials with humans.
In the absence of human studies, hundreds of recent, peer-reviewed studies published in the most elite scientific journals have linked low level exposures of Bisphenol A, for example, to cancer, obesity, diabetes as well as reproductive and developmental harm (further reading here).
Despite those links and overwhelming associations, it remains scientifically incorrect to state that BPA causes any of those maladies.
This is because “linked to” and “associated with” are not as definitive as “causes” of a disease or syndrome. Correlation does not equal causation.
Correlations — as discovered by the science of epidemiology — have often saved many lives by pointing scientists to look for the causal links for many diseases and syndromes including cholera and AIDS (further reading here). But epidemiology is not definitive.