Attorney Jim Love of the IAOMT
In its Final Rule on amalgam in 2009, the FDA relied on a 1995 EPA risk assessment for mercury, which relied principally on a study by Fawer, et al., in establishing a reference concentration of 0.3 µgs/m?. EPA's reliance on Fawer was criticized by the Petitioners because Fawer studied workers at a chlor-alkali plant.
Dr. Richardson criticized EPA's reliance on Fawer, et al., on the basis that the presence of chlorine gas reacted with mercury vapor. The resulting mercuric-chloride did not absorb as well as mercury vapor and did not have the same pharmacokinetics. FDA asked its Committee whether the exposure-response relationship for mercury vapor was modified by concomitant exposure to both mercury vapor and chlorine gas.
Dr. Griffin of the EPA argued that the issue wasn't worthy of consideration because 250 subjects were considered in the course of three studies, not one, and only 12 of the 250 workers were chlor-alkali workers. The balance of the subjects were dentists and fluorescent lamp workers who were not exposed to chlorine gas.
Dr. Richardson, who had already spoken to the Committee, was not allowed to address this comment, but he later communicated his objection to Michael Adjodha of the FDA.
Dr. Richardson's comments are set forth below:
Dr. Richardson further noted:
Dr. Richardson concluded:
In preparing his 2009 risk assessment for mercury, Dr. Richardson relied on Ngim, et al., which did not rely on the study of workers from the chloralkali industry. The paper also represented the lowest reported LOAEL. Dr. Griffin stated that the goal of REL development was to identify the study that had critical effects at the lowest level; and that basing the RfC on this 'most sensitive study' helps protect against effects observed at higher levels.
So, Dr. Richardson's concern for use of chloralkali workers was not a red herring. In fact, the Ngim, et al. study reported the lowest LOAEL of the studies relied on by EPA, and has no confounding interference by concomitant chlorine gas exposure. Neither Dr. Griffin nor FDA has since commented on Dr. Richardson's criticisms. As we stated in our Petition, reliance on Fawer, et al. is misplaced.
Dr. Ismail supported the view of the Petitioners that the literature needed to be updated between 1992 and 2010, and that it was inappropriate to rely on a 1995 EPA RfC while ignoring the many years of published research during this period.  Dr. Bates agreed with Dr. Ismail. 
MERCURY EXPOSURE HAS TRIED TO CONTACT DR GRIFFIN FOR COMMENT (7/20/2011), BUT SHE HAS NOT RESPONDED AT THE TIME OF THIS POSTING.
DR. GRIFFIN: I would like to -- I'd like to correct something here before we go on because it's going to have a big impact. The statement that the quantitative reference concentrations based on chloralkali workers is wrong. As mentioned earlier, there's a qualitative and a quantitative aspect to development of a toxicity value.
When we amassed the literature, the predominant occupational studies were chloralkali workers, and from those studies it was determined that neurological effects were the critical effects.
The next step was then to develop a critical effect level. Three studies were used to develop the critical quantitative effect level. Approximately 250 people total from the 3 studies, of which only 12 were chloralkali workers, the rest were dentists, fluorescent lamp workers. And so this issue about the interference of chlorine with the mercury, it's a red herring. It's really not worthy of this Panel to have to discuss. The issue of Nimm versus Fawer is really a silly issue because Nimm was one of the studies used to develop the EPA reference concentration.
So I just wanted to set the record straight before we proceed down this path. And this is not opinion; it's page 5 of the IRIS chemical file for
DR. JEFFCOAT: That's very helpful, thank you.
Do we have other comments? Yes.
DR. ASCHNER: My question is actually for Dr. Griffin. Did you say that this was based on neurological effects? Why would it based on neurological effects and not more sensitive organs like kidney?
DR. GRIFFIN: The bulk of the literature was evaluated. Again, if you go to the IRIS chemical file you will see that there are also studies that do at look at renal function. We looked for the effect which was occurring at the lowest doses consistently in the population and the central nervous system effects were occurring at much lower doses than the renal effects. And again, it's in the file.
DR. JEFFCOAT: Yes, Dr. Ismail.
DR. ISMAIL: To move the discussion forward, I think we --
DR. JEFFCOAT: Yeah, we need to --
DR. ISMAIL: -- we accept what Dr. Griffin has said; however,
there is a need for update of -- update of the literature to do a review from 19- -- I think last study was in the '80s -- to update from 1992 until 2010 what was -- has been published that could contribute or add to the body of -- the weight of evidence that you have, the EPA have used. And that's --
DR. JEFFCOAT: Other comments?
DR. DOURSON: I have a comment.
DR. JEFFCOAT: Yes.
DR. DOURSON: Michael Dourson. I concur with Dr. Griffin. The IRIS file is clear in its interpretation; it is multiple studies.
DR. JEFFCOAT: Other comments? Oh, sorry.
DR. BATES: Michael Bates. I agree with Dr. Ismail that the studies that are being considered are pretty old and there are some newer studies. And one thing I would like the Panel to consider is the possibility of using a more continuous relationship than just simply compare -- studies which compare an exposed group with an unexposed group. And one the speaker's used today,
Dr. -- I'm blanking -- Ginsberg, yes, mentioned that. And he also mentioned the study by Echevarria et al., and actually that gives a continuous relationship. This actually has more information than just comparing one group with another. So of course, this might not lead its -- lend itself to an RfC or an REL but nonetheless there is more information in it when you look at a continuous measure.
And I believe there are other studies probably out there that, you know, have these -- this continuous data. And particularly if the data could be combined across studies it could be very helpful.