OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION **UNITED STATES ENVIRONMENTAL PROTECTION AGENCY**

WASHI NGTON , D.C., 20460

September 20, 2011 **MEMORANDUM Subject:**  Response to Comments on the Preliminary Problem Formulation for the Ecological Risk and Drinking Water Exposure Assessments for Cry olite (PC Code 075101; DP Barcode 383606) **To:** Molly

Clay ton, Risk Manager Reviewer Risk Management and Implementation B ranch 3 Pesticide Re

- evaluation Division **From:** James Hetrick, Ph.D., Senior Science Advisor

Melissa Panger, Ph.D., Senior Biologist Dana Spatz, Branch Chief Environmental Risk Branch 3 Environmental Fate and Effects Division Office of Pesticide Programs This memorandum provides a response to public comment on the Registration Review Preliminary

Problem Formulation for the Ecological Risk and Drinking Water Exposure Assessments for Cry olite (PC Code 075101; DP Barcode 383606). Comments were rec eived from the Fluoride Action Network (FAN) (7/5/11). The comments will be addressed according to topic headings in the comment document. 3.4.1. OPP should require that testing for adverse effects include cryolite and **all** of its degradation products and complexes. **FAN Comment:**  The FAN believes that cry olite use will el ev ate the aluminum and fluorine concentration s to levels of toxicological concern. They contend the Agency

did not adequatel y address the environmental chemistry of aluminum. Additionally , they believe the sy

nthetic cr yolite is chemical ly different than natural cry olite due to the presence of impurities including aluminum oxide, aluminum fluoride, lithium fluoride, magnesium fluoride, calcium fluoride, quartz, and iron oxide. They referenc e MSDS data sheet s stating degradation of fluoro

complexes (at acidic pH), hy drox yl

- aluminum (at environmental pH), and fluorhy dric acid

.**EPA Response:** The introduced F - , Al 3+ , and Na + from cry olite dissolution will be incorporated

in to the natural b iogeochemical cy cles in the soil and aquatic environments. Mechanisms controlling environmental concentrations of F - , Al 3+, and Na+ include sorption, mineral precipitation, and ligand complexation. The formation of fluoro

- complexes and hy droxy l

aluminum complexes will occur regardless of the application of cr yolite

. These complexes occur naturally in soil and water environments. The relative proportion of the fluoro

- complexes is highl y dependent on the F

- concentration. I n the absence of fluoride precipitation, the fluoro

complex (AlF 3 ) is the predominate inorganic Al complex. However, the precipitation of fluorite (CaF 2 ) changes the distribution of fluoro

- complexes and hy dr oxy l

- aluminum complexes

. The fluoro

- complexes are only predominate in acidic environments (pH<6.4). In near neutral and alkaline environments (pH>6.4), the hy drox yl

- aluminum complexes Al(OH)3 and Al(OH) 4 - are predominate. These data indicate the fluo ro - complexes of aluminum should be important in acidic environments.

pH 3 4 5 6 7 8 9MoleFraction

0.0 0.2 0.4 0.6 0.8 1.0 Al3+ AlOH+2 Al(OH)2+ Al(OH)3 Al(OH)4- AlF+2 AlF2+ AlF3 AlSO4+

pH 3 4 5 6 7 8 9MoleFraction

0.0 0.2 0.4 0.6 0.8 1.0

**Figure 1: Mole Fraction Diagram s**  **for Al 3+**  **and fluoro**
**- complexes and hydroxyl**  **- aluminum**  **complexes. (Equilibrium conditions assumed are log (SO 4**  **2 -**  **)=**
**- 4 M**  **. Top Graph**  **) No F**
  ** precipitation assumed. Bottom** **Graph ) Fluorite precipitation assumed.** As stated in the problem formulation, the incremental addition of cr yolite is not expected to

cause elemental exceedance of natural background concentrations, especia lly for aluminum and sodium (Table 1 ). More importantly , chemical equilibrium in soil and aquatic environments is expected to buffer concentrations of Al 3+ and F -

. **Table 1**  **. Relative contribution of elemental components from cryolite**  **application to soil .**  Elemental Components Elemental

Fraction Elemental

Maximum Application Rate (lbs/A) 1 Elemental

Maximum Application Rate (mg/kg) 2 Average

Elemental Concentration in Soil (mg/kg) Al 0.13 19.97 9.985 71000 F 0.55 84.48 42.24 200 Na 0.32 49.15 24.58 6300 T he chemistry

of Al 3+ in soil solution is controlled by the aluminum oxide minerals (Lindsay, 1979). In contrast, the fluoride concentration in soil solution may be controlled by

fluori de min erals such as fluorite (CaF 2 ), fluorphlog opite (KMg 3 AlSi 3 O 10 F 2 ), and fluoroapatite (Ca 5 (PO 4 ) 3 F). Figure 2 illustrate s that free ion concentrations of F and Al 3+ from cry olite dissolution in soil will be supersaturated to fluorite and gibbsite (γ

- AlOH 3 ). ). From a single application of cry olite , the theoretical soil solution concentration of total fluoride and aluminum is 0.01111 moles/liter ( 210 mg/L) and 0.00185 moles/liter ( 49.91 mg/L)

. Thermod ynamic equilibrium will cause precipitation of the dissolved fluorite and gibbsite in soils.pH 2 3 4 5 6 7 8 9 10log(F-)

-10 -8 -6 -4 -2 0

Fluorite-Soil Ca Fluorite-CaCO3 (0.003 M CO2) Fluorite-CaCO3 (0.0003 M CO2) Theoretical Soil Fluoride Concentratio **Soil Solution Fluoride Concentration**

**Supersaturation**

**Supersaturation**

pH 3 4 5 6 7 8 9log(Al3+)

-20 -15 -10 -5 0 5

Amorp Al(OH)3 Gibbsite Theoretical Soil Solution Al3+ Concentration **Supersaturation**

**Figure 2**  **: Mineral Stability Diagrams with**  **Theoretical Soil Solution Activity of F**
**- and Al3+**  **from a Single Cryolite Application** A review of NAWQA water qualit y data provide s an indication of F and Al 3+ concentrati ons in ambient waters. The median concentration of detectable F - and Al 3+ in NAWQA samples (2000

- 2010) was 0.241 mg/L (n=7574 samples) and 5.89 ug/L (n=1274 samples), respectivel y. These data illustrate the background concentration in the surface waters

. 3.4.5. (in the summary ; “3.5.5.” in the text). OPP has failed to include amphibians in the Ecological Risk Assessment. **FAN Comment:**  As described in the cry olite Problem Formulation, OPP uses a surrogate approach in its ecological risk assessments ( i.e ., OPP assumes that toxicity to birds is similar to terrestrial

- phase amphibians and reptiles and that cry olite toxicity to fish is similar to aquatic

phase amphibians). The FAN states that the se toxicity assumptions “... ignore that amphibianshave been shown to be extremely sensitive to toxins, and are considered ‘valuable indicators of environmental stress’ (p. 4, FAN comments, 2011). They state that OPP should require cry olite toxicity data on amphibians and conduct a risk assessment for amphibians in the cry olite risk assessment conducted for Registration Review. **EPA Response:** A s discussed in the response to 3.4.1. above, the incremental addition of cr yolite is not expected to cause elemental exceedance of natural background concentrations, especi all y for aluminum and sodium , in soil or water. More importantl y, chemical equilibrium in soil and aquatic environments is expected to buffer concentrations of Al 3+ and F -

. As a result , exposure to amphibians to aluminum , fluorine or sodium from cry olit e use, either via contact with soil or in the aquatic environment, is not expected to exceed normal backgro und levels for these elements . Therefore, additional toxicity data using amphibians would not likely alter cr yolite risk conclusions. Therefore, EF ED does not recommend requesting toxicity data on amphibians for the cry olite ecological risk assessment conducted for Registration Review

. 3.4.6 . (in the summary ; “3.5.6.” in the text). OPP should require reproductive/developmental toxicity/teratogencity testing for terrestrial and aquatic species. **FAN Comment:**  “ OPP assumes that because cryolite is “practicall y nontoxic to avian species on an acute oral and sub

- acute dietary basis” an d is “no more than slightl y t oxic to small mammals on an acute oral basis” (EPA OCSPP, 2011a, p. 13) that chronic risk to birds and small mammals is not expected. However, it is well known that the developing embry o and fetus is much more vulnerable to to xins than is the adult form. Furthermore, for all but mammalian species, acute exposure of the fema le at the time of ovulation and fertilization potentially establishes a situation of chron ic exposure for the duration of embry ological development. Thus OPP should req uire reproductive/developmental toxicity /teratogenicity

testing for all representative terrestr ial and aquatic species exposed to cry olite and all of its degradation products and complexes. ” **EPA Response:** As discussed in the response to 3.4.1. above, the incremental addition of cr yolite is not expected to cause elemental exceedance of natural background concentrations, especiall y for aluminum and sodium , in soil or water. More importantl y, chemical equilibrium in soil and aquatic environments is expected to buffer concentrations of Al 3+ and F -

. Therefore, additional toxicity data using aquatic animals would not likely alter cry olite risk conclusions . Therefore, EFED does not recommend requesting additional toxicity data on aquatic animals f

or the Registration Review ecological risk assessment for cry olite

. EFED, however, does agree that there is a potential for terrestrial animals to be exposed to cr yolite via ingestion of vegetative dietary items that have been treated with cr yolite (either directly or via spray

drift)

. Additionally , due to cry olite’s use pattern, there is a potential for repeated exposure to cryolite (cry olite can be applied to crops several times per season). Therefore, EFED agrees that risk to birds and mammals from chronic exposure via the ingestion of contaminated vegetative dietary items should be assessed in the risk assessment conducted for cr yolite for Registration Review.There are currently acceptable reproductive toxicity data available for mammals (a two
generation rat study ; MRID 43387501 1 ). These data will be used in the cryolite ecological risk assessment to assess potential risks to mammals from repeated exposure to cry olite . No chronic toxicity data for cry olite are currentl y available for bird s. Therefore, to adequately assess risks to birds from potential repeated exposure to cry olite, EFED recommends that an avian reproduction study (850.2300) be conducted for cry olite. 3.4.7. (in the summary ; “3.5.7.” in the text). OPP should require chronic toxicity testing for aquatic animals. **FAN Comment:**  FAN requests that additional toxicity data on aquatic animals (chronic data) be conducted due to the potential for chronic exposure to cry olite in aquatic environments due to cr yolite’s use patte rns. **EPA Response:** As discussed in the response to 3.4.1. above, the incremental addition of cr yolite is not expected to cause elemental exceedance of natural background concentrations, especiall y for aluminum and sodium , in soil or water. More importantl y, chemical equilibrium in soil and aquatic environments is expected to buffer concentrations of Al 3+ and F -

. Therefore, additional toxicity data using aquatic animals would not likely alter cry olite risk conclusions . Therefore, EFED does not recommend requesting additional toxicity data on aquatic animals for the Registration Review ecological risk assessment for cry olite

.

1 MRID 43387501. Schroeder, R. E. (1994). A Tw o - Generation Dietary Reproduction Study in Rats with Kryocide (Cryolite). Pharmaco LSR, Inc. Toxicology Services North America, New Jersey 08875

- 2360.