UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON , DC 20460 OFFICE OF CHEMICAL SAF ETY AND POLLUTION PREVENTION
PC Codes: 050507, 034902 DP Barcode: 421836 Date: August 19 , 2014 MEMORANDUM Subject:
To:

From: Registration Re view Preliminary Risk Assessment for Ferric and Ferrous S ul fates Katherine St. Clair, Risk Manager Reviewer Cathryn Britton, Team Leader Kevin Costello, Branch Chief Risk Management and Implementation Branch 2 Pesticide Re-E valuat ion Division (7508 P) Office of Pesticide Programs ..11 j 

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... 04/ \-- Edward Odenkirchen, Ph.D., Senior Science Ajvi sor \ 

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## tl '{ Sujatha Sankula, Ph .D ., Branch Chief

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# =- Environmental Fate and Effects Division (7507P) Office of Pesticide Pro grams
The Environmental Fate and E ffects Divi s ion (EFED) h as compl eted a condensed preliminar y risk assessment fo r ferrou s and ferr ic sulfates in support of Registration Review
. Discus sion with the Pesticide Re -Ev aluatio n Di vi sion ri sk managers lead to a condensed preliminary ris k assessment approach th at evaluated the risks in the context of past risk assessments supporting regulatory decisions and a determination if new uses or new data would alter the previous risk conclusions. This assessment relies on the previous Registration Eligibility D ocument (RED) for Iron Salts (http: //www.epa.gov/oppsrrd 1 / REDs/old reds /iron salt.pdf), the EFED Registration Review Problem Formulation for Ferrous Sulfate Monohydrate and Ferric Sulfate (Iron Salts) (D358772 , http: //www.regulations.gov/# !documentDetaii;D=EPA -HQ- O PP -2008

- 0626-0004), an d EFED's reviews of terrestrial plant seedling emergence an d vegetative vigor studies categorized as supplemental for both chemicals (DP Barcodes: D 399697, 400115 , 404679) and honeybee adult acute contact studies categorized as supplemental for limit tests, acceptable for the ferrous sulfate dose

-response test and supplemental qualitative for the ferric su lfate dose-response test (DP B arcodes; D 392671, 392679, 393680, 406105) submitted in response to the Registration Review D ata Call -Ins (http: //www.regulations.gov/#!documentD etaii;D =EPA-HQ-OPP-2008-0626-00 14 and http: //www. reg u lations.go v/# !documentDetail:D=EPA-HQ-OPP-2008-0626-00 13 ).Background Iron is the fourth most abundant element and the second most abundant metal in the earth's crystal rocks. Iron occurs in a wide variety of minerals, and it is present in foods naturally and through added ingredients. Ferrous sulfate (or iron (II) sulfate, FeS04) is known as the monohydrate, FeS04·H20; the tetrahydrate, FeS04-4H20; the pentahydrate, FeS04 · 5H20; and the heptahydrate, FeS04 ·7H20
. The heptahydrate is also called green vitriol, copperas, o r melanterite (a mineral that commonly occurs with pyrite). It is a blue-green monoclinic crystalline water-soluble salt. It is prepared commercially by oxidation of pyrite (iron sulfi de) or by treating iron with sulfuric acid. F errous sulfate monohydrate is a white, monoclinic, crystalline powder that occurs naturally as the mineral szomolnokite. Iron (II) sulfate is most commonly encountered as the blue-green heptahydrate. Iron (II) sulfate can be found in various states of hydration, and several of these forms exist in nature.
• FeS04· H20 (mineral: szomolnokite) • FeS04·4 H20 • FeS04 · 5 H20 (mineral: s ideroti l) • FeS04·7 H20 (mineral: melanterite) Ferric sulfate (or iron (III) sulfate , Fe2(S04)3) is a ye llow rhombic crystalline hygroscopic water soluble salt that decomposes when heated to a temperature of 480°C. Iron salts are herbicides used primarily to control mosses. There are 16 products containing ferrous and ferric sulfates. For ferrous sulfate the end use products are formulated as a granular for terrestrial non-food and outdoor residential u se ornamental herbaceous plants, lawn s and turf, woody shrubs and vines. Ferrous sulfate is applied by hand or spreader at a single ac tiv e ingredient rate of 1 to 4 .7 lb/1 000 ft2

. For ferric sulfate, the end use products are formulated as soluble concentrate /liquid (4.5-95.4% a.i.) for terrestrial nonfood use on ornamental lawns and turf and outdoor residential sites at a single active ingredient rate of 0.74to 2.03 lb/1000 ft2

. It is applied by sprinkler can and hose-end-sprayer. Previous RED and Current Registration Review Risk Conclusions for Terrestrial Vertebrates and Aquatic Taxa The RED evaluated the current lawn and turf uses of these two compounds for the control of moss. These uses include granules and hose-end or watering can applications. The RED indicated no risk concerns for the labeled uses of ferrous and ferr ic sulfates to terrestrial vertebrates or animals, and aquatic plants. A review of the Problem Formulation documents' lis tings of uses for the two chemicals and the summarized toxico logical and environmenta l fate data indicate nothing has fundamentally changed since the completion ofthe RED risk assessment. Therefore, EFED concludes that the finding of no concerns for direct effects to te rrestrial vertebrates or aquatic plants and animals found summarized in the RED still remains accurate. 2Terrestrial Plant Risk Lines of Evidence and Conclusions The RED did not assess the risk to terrestrial plants for ferrous and ferric sulfates and plant studies were identified as data gaps in the Problem Formulation for both chemica ls. The Environmental Fate and Effects Division (EFED) reviewed fou r T ier 1 screening terrestrial plant toxicity studies for ferrous sulfate (MRIDs 48650801, 4888050 I) and ferric sulfa te (MRIDs 4873880 I , 487340 I) in support of Registration Review. The terrestrial plant studies were considered to provide sufficient information to support a Registration Review risk assessment but were classified as supplemental owing to the fact that they could not demonstrate a NOEC in all tested species. A current understanding of the use patterns for the two chemicals shows that uses are confined to watered in (watering can or hose end sprayer) and granular applications to lawns and turf. These application scenarios are not over the top spray appl ic at io ns so spray drift loading to adjacent areas to the u se site is not expected
. Moreover, EFED does not expect that runoff loadin gs will be s ignificant to any degree b ecau se the compounds are expected to ionize and any resultant iron runoff is expected to be exceedingly low , ca. 4 X I 0-7 mg/L, and largely masked by natural iron background (communication between James Hetrick Senior Science Advisor, USEPNO PP/EFED/ERB3 and Meghan Radtke, Risk Assessment Process Le ader USEPNO PP /EFED/ERBl, June 9, 2014). Consequently no complete exposure pathway, drift or runoff , of the applied ferric su lfate or ferrous sulfate is expected to off-site plants. In light of this understanding of the exposure pathways for non-target plants, EFED concludes that there are no concerns for direct effects to terrestrial plants. Pollinators and Terrestrial Invertebrates Risk Assessment and Conclusions Toxicity of Compounds to Honey Bees (and by surrogacy other terrestrial invertebrates) The RED did not assess the risk to terrestrial arthropods and pollinators for ferrous and ferric sulfates and honeybee effects studies (the surrogate species for pollinator and arthropods risk assessment) were identified as data gaps in the Problem Formulation for both chemicals. A total of four honeybee st udies were submitted to EPA for review. Two studies were l imit studies with ferric sulfate (MRID 48548701) and ferrous sulfate (MRID 48549601) tha t

· demonstrated mortality to bees at the limit of25 ug ai/bee. These were classified supplemental.

Two dose response studies were submitted to the Agency , reviewed and found to be acceptable for ferrous su lfate for quantitative use and supplemental for qualitati ve use for ferric sulfate; the later finding with ferric sulfate owing to a split dosing design that limits the statistical confidence in the results:

• Acute Contact-Dose response study ferric sulfate (MRID 48935401, supplemental qualitative): 96-h LDso 235 uglbee • Acute Contact-Dose response study ferrous sulfate (MRID 4857860 I , acceptable): 96-h LDsa >I 00 uglbee ; NO EL I 00 uglbee 

### 3Exposure Assessment/or Bees (and other terrestrial invertebrates by analogy) EFED emp loyed the following contact exposure assessment model from avail able policy: Honey bee adult contact exposure ug/bee = (application rate lb/acre) (2.7) Maximum residues in treated areas receive pesticide treatment were estimated us ing this model as follows:
• Ferric sulfate Maximum application 2.03 lbs/ 1 000 ft2 = 90.2 lbs/acre X 2. 7 = 244 ug/bee
• Fer rous sulfate Maximum app lication 4
. 675 lbs/1 000 ft2 = 203.6 lbs/acre X 2
.7 =550 ug/bee Bee Comparison ofToxicity Values to Exposure Estimates (and screening level assessment for other terrestrial invertebrates) The ratio of exposure to availab le effects information for honeybees is as follows for the two compounds:
• Ferric sulfate (presumptive ratio as effect values canno t provide a definitive quantitative endpoint due to statistical limitations) 244 ug/bee exposure level exceeds effect estimate of235 ug/bee by a factor of 1
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• Ferrous sulfate (presump tive ratio as RQs cannot be definitively established without LDso) 550 ug/bee exposure level exceeds effect es timate by less than a factor of 5
. 5 Bee Risk Characterization (limited analogy for individuals of other terrestrial invertebrate species) In neither case can the uncertain ra t ios provided above be directly compared with the Agency Level of Concern (LOC) for acute honeybee risks of 0.4 or greater. However in both cases it appears that exposure levels are in excess ofthe best available es timates available for lethal toxicity. There i s poss ib le concern for bees directly contacted b y spray applications on lawns and turf if attractive flowering plants are also present. However, given the herbicidal nature of ferric sulfate, the likely low attraction of moss for honeybees, and an expectation that the lawn and turf uses are targeted to small treatment areas, any given app lication of the compound is not likely to resu lt in hive impacts. The f erro u s sulfate exposures exceed the maximum tested level by a factor of five; however, this value was shown to produce no adverse effects at this concentration. Because exposures to ferrous sulfate are so muc h higher than the NOEC it is n ot possible to defi n itively establis h the risk concerns. However, cons ideration of the supp lemental acute limit study wi th honey bees in which 48% of the tested bees died at an exposure of25 ug/bee (MRID 48549601) wou ld suggest that acute effects are possible though the observation of mortali ty in the limit study is 4confounded by high mortality in the controls, suggesting that the 48% fi gure might be overinflated. If one assumed that ferrous sulfate was roughly equivalent to ferric sulfate in bee toxicity**(i.e.,~200** to 300 ug/bee for an 

### LDs o), there still would be concerns that exposures in the field would exceed acute toxicity thresholds. The se toxicity considerations combined with a low attraction of moss to bees, the herbicidal effects of iron salts to bee attractive plants preventing bee attraction, and the expected limited geographic extent for any given app lica tion of the compound, any possible bee effects would be incidental and not likely to result in hive impacts. Concerns for ferric sulfate effects on individual honey bees contacting sprayed areas is weakly supported by the available data. Multiple lines of evidence would suggest that both compounds may lethally affect bees in treated areas. Consideration of the uncertain effects thresholds, the low attraction of target mossy areas for bees, and the expected low geographic extent for any given application of the compounds applied to the intended use areas wou l d suggest that any putative bee effects would not rise to a level where hives would be impacted.
Potential for Effects to Federally Listed (Threatened and Endangered) Species. Consistent with the RED and without any additional inf ormation, EFED finds no direct effect risk concerns for listed and non-listed terres trial vertebrates or any aquatic organisms. A reevalua tion of the nature of the uses of ferric and ferrous sulfates suggests that exposure pathways to off-site vegetation are inconsequential and so there are no concerns for direct effects to non -target terre strial plants. Therefore, this risk assessment indicates that there are no effects to Federally listed terrestrial vertebrates and plants and aquatic organisms associated with the registration of ferric and ferrous sulfates in accordance with existing labels. The available data on effects to honey bees would suggest locali zed acute effec ts are possible. Many of the limiting risk factors in the honeybee assessment are transferable to a risk characterization for lethal impacts: hi ghly uncertain lethali ty to tested invertebrates, low attractiveness of the target areas, and low geographical extent of treatment. Considering these line s of evidence along with an absence of spray rift and no appreciable runoff, the immediate area of application to moss, on residential and turf areas, constitutes a very limited geographical extent of exposure (the materials are applied by watering can or hose end sprayer). It is not reasonable to assume that listed invertebrate species will be in the immediate proximity ofthese application s ites and so effects are not reasonably expected to occur for Federally listed terrestrial invertebrates.

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