Fallon:
Coincidentally with the assignment, the CDC issued its report on Fallon:
http://www.cdc.gov/nceh/clusters/Fallon/1_ExecutiveSummary.pdf
A careful reading of the study indicates that no environmental agent was identified as causing the cancer cluster. There were indeed high levels of arsenic and tungsten, but these were high in the healthy as well, in fact the sick had less of them.

Here is an interesting side issue: http://www.foxnews.com/story/0,2933,80460,00.html "Clusters" are made to order for "lawyer-mediated toxicology." Attorneys who hope to make large fees by representing the "victims" try to find a "culprit" with deep pockets, like an oil company, to sue. Once they get it to a jury, they arrange for the matter to appear as the wealthy company versus the poor, sick, or injured party, and American juries award large amounts of money to the party, whose lawyer gets the majority of it. These lawyers "advertise" by pumping up the matter in the press.

Having said that, which the FOX articles provides details for, we are still left with the question, how can there be 15 cases of a disease that is not common, in a region with 8500 residents? There are several explanations, any of which I would satisfied with, if it were 5 cases in Fallon.
1. Clusters just occur. A statistician can prove that there is a probability that some random events will occur in clusters. That is, "randomness" is not uniform (huh?).
2. Clusters are noticed.
3. Increased diagnosis. Some human diseases have a long latency period. Once a cluster is suspected or publicized, other will seek diagnosis.
4. Some human diseases are not noted by the patient, who would spontaneously recover, absent the diagnosis.
6. Physicians are prone to fads.

The take-home message is that a "cluster" is certainly not a "cause" and might not be an "effect." The 15 cases in Fallon is amazing.

Words.
Careful with the word "absorbed," which implies something is taken into, which is different than "adsorbed," which implies something remains on the surface. If you don't know which, the word "sorbed" is preferred.

New parameter words.
Q. A couple of questions I still have on this parameter is what does "non-retarded" mean?
A. This parameter is used in the groundwater transport part of the model and is probably part of "retardation factor" for particular chemicals that flow slower than the water because they are "retarded." This is different than degradation that removes the contaminant.
Q. And could dissociation constants be used as values for a given pH, if not how is this parameter different?
A. If you knew the pH, you could set the parameter to whatever you thought it should be.

Q. There is no calculated RfC for Dicamba.
A. Yes indeed. There are many chemicals for which the RfC or RfD is not known or expressed. Inhalation experiments are more difficult and expensive in the laboratory than oral.