The Neighborhood Toxicologist: Bisphenol A in the news again

Monday, December 10, 2007

Bisphenol A in the news again

For those interested in reading more about the estrogenic plasticizer bisphenol A (BPA), the Milwaukee Journal Sentinel just published its own review of BPA literature in response to the recently released National Toxicology Program (NTP) report, which according to the Sentinel, found "bisphenol A to be of some concern for fetuses and small children. It found that adults have almost nothing to worry about."

The article discusses conflicting conclusions by two different panels one convened by the NTP the other by National Institutes of Environmental Health and Safety) and NTP's recently released BPA report.

The Sentinel analyzed 258 studies, although a search of the links provided along with the article didn't lead to a list of those articles, nor the depth of their analysis, and who actually did the analysis, they do provide a graphic summarizing general conclusions of each study (found an effect, vs. did not find effect or were not looking); the dose range (low verses high); and the funding agency for each study (industry, nonindustry.)

If you want to read more about the scientific reports (those produced by government panels rather than the Sentinel), check out what J.Lowe has to say over at Impact Analysis in his blog about the "Tangled story of bisphenol A."

Cross posted from the earthportal forum

1 comment:

Anonymous said...: Great work.; 4:13 PM

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Some history: Toxicology as a formally recognized scientific discipline is relatively new (mid 1900’s) although the science itself is thousands of years old. Consider the potential results of early trial and error experiences of hunter-gatherers for whom identifying a toxic plant or animal was a life or death situation. Some of the most poisonous substances known today are naturally produced chemicals including Ricin from castor beans or tetrodotoxin from the puffer fish. Early humans’ careful observation of plants or animals with toxic characteristics such as frogs containing curare, were put to use not only for avoidance of toxic substances but for weapons as well. Additionally, many naturally derived poisons were likely used for hunting, medicinals (the Egyptians were aware of many toxic substances such as lead, opium and hemlock as early as 1500 BCE), and eventually for the political poisonings practiced, for example, by the early Greeks and Romans.

As humans sought to better understand natural compounds that were both beneficial and harmful, there was very little if any clear understanding of the fundamental chemical nature of substances. That is, there was no connection between the ‘extract’ or ‘essence’ of a poisonous plant or animal and any one particular chemical that might cause toxicity. In fact, an awareness of chemistry in its modern form did not occur until the mid to late 1600’s[i]. So it is ironic that Paracelsus, a physician from the sixteenth century and one of the early “Fathers of Toxicology” had no clear understanding of chemistry as we know it today. He along with many others at that time apparently believed that all matter was composed of three “primary bodies” (sulfur, salt, and mercury)[ii]. Yet Paracelsus also coined the now famous (or infamous) maxim of the newly emerging discipline of toxicology:

“All substances are poisons, there is none which is not a poison. The right dose differentiates a poison from a remedy.” (Paracelsus,1493-1541)

This phrase and Paracelsus’ name are committed to memory by hundreds of new toxicology students each year and has become the ‘motto’ of toxicology. Interestingly, if one takes Paracelsus at face value, it appears he was referring to potential remedies. This is an important point, since in recent years some have turned this around to suggest that exposure to very small doses of highly toxic chemicals (such as dioxins) might not be an problem! These days most of us are well aware of the fact that overdosing can turn remedies to poisons, even with apparently innocuous drugs such as aspirin and Tylenol.

[i] Ball, P. 1999. Life’s Matrix: A Biography of Water. Farrar, Straus and Giroux, NY, NY.

[ii] Ball, 2001.