Fluoride Action Network

Thiessen: 2006 Submission to EPA on Sulfuryl Fluoride

August 2006 | By Kathleen M. Thiessen PhD

General Comment: Re: Dockets EPA-HQ-OPP-2005-0174 and EPA-HQ-OPP-2003-0373

Dear Sirs:

Regarding the requested stay of tolerances for sulfuryl fluoride, I would like to make a few brief comments. I regret that I have not had the time to give you a more complete review of the proposed tolerances.

First, it was inappropriate to base the tolerances for sulfuryl fluoride on the existing MCLG/MCL of 4 ppm fluoride in drinking water. That is a standard intended for the protection of adult health and was never designed for the protection of children’s health. The appropriate standard, in principle, would have been EPA’s RfD (currently 0.06 mg/kg/d, based on an assumed NOAEL of 1 ppm fluoride in drinking water; http://www.epa.gov/iris/subst/0053.htm).

Second, a National Research Council committee, of which I had the honor of being a member, recently reported that an MCLG of 4 ppm fluoride in drinking water is not protective of human health. So even if that standard were the appropriate one for use in deriving pesticide tolerances, the current value is not protective of human health.

Third, it is my professional opinion that an RfD of 0.06 mg/kg/d is not protective of human health, particularly not for some population subgroups. The NRC committee was not charged to evaluate that standard, but the report contains considerable information which, if handled by EPA’s ordinary risk assessment procedures, would lead to a much lower value for the RfD.

Fourth, a considerable fraction of the US population, especially infants and children, already has fluoride intakes exceeding 0.06 mg/kg/d, without consideration of a contribution from sulfuryl fluoride residues. Information on fluoride intakes for average or typical conditions and for certain population subgroups is contained in the NRC report and is relevant to the current context of setting limits on an additional source of fluoride exposure.

Finally, EPA should take care to ensure that tolerances for specific foods are appropriate for the amounts of those foods actually consumed by people who consume them. For example, many or most people probably have a very low intake of powdered eggs, while some individuals could have a regular intake of meal-sized amounts. The fluoride tolerance for a given food type must be protective for an individual who regularly consumes that food type, not for an “average” consumption rate based on many individuals with little or no consumption of that food type.

Sincerely yours,
Kathleen M. Thiessen, Ph.D.
Senior Scientist, SENES Oak Ridge, Inc., Center for Risk Analysis
Oak Ridge, Tennessee