OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460

February 2 5 , 2016

PC Code: 076702

DP Barcode: 429260

MEMORANDUM

SUBJECT : Combined Problem Formulation and Pr eliminary Risk Assessment in Support of the Registration Review of Lime Sulfur

TO : Katherine St. Clair, Chemical Review Manager Kevin Costello, Branch Chief Risk Management and Implementa tion Branch II

Pesticide Re

- Evaluation Division (7508P)

FROM : Karen Milians, Ph.D., Chemist Andrew Sayer

, Ph.D., Biologist

Environmental Risk Branch IV Environmental Fate and Effects Division (7507P )

REVIEWED BY : T homas Steeger, Ph.D., Senior Science Advisor

BY Jim Carleton, Ph.D., Environmental Scientist

Environmental Risk Branch IV Environmental Fate and Effects Division (7507P )

THROUGH : Jean Holmes

, DVM, MPH, Branch Chief

Environmental Risk Branch IV

Environmental Fate and Ef fects Division (7507P )

This memorandum transmits the combined problem formulation and preliminary ecological risk

assessment in support of the R egi stration R eview of calcium polysulfides (PC Code 076702)

hereafter referred to as lime sulfur

. The problem formation and preliminary risk assessment (PRA)

w ere co mbined because the current data base is considered to be sufficient to support the Registratio n Review of lime sulfur given the relatively limited use of the compound as a pesticide

. T h e PRA i dentifies potential risks to non

- target organisms ; however, for many of these taxa, the risk is considered low given the low likelihood of exposure

.

The environmental fate and ecological effects of lime sulfur when used as a f ungicide/acaricide

were pre viously evaluated in 2005 to support the Reregistration Eligibility Decision (RED ; DP- Page 2 of 30

- Barcode D313165 ) of inorganic p olysulfides 1

. Since the 2005 RED, no additional data have been provided to EPA and risk estimates have not changed from those identified in the RED

. While acute risk quotients (RQs) exceed levels of concern (LOCs) for aquatic and terrestrial animals, the likelihood of actual exposure to residue s at levels capable of causing adverse effects in these

animals is consider ed low. There is uncertainty however regarding the potential for adverse effects to terrestrial invertebrates exposed to lime sulfur from applications made at bloom to pollinator

attractive trees, i.e., apples . Although available contact toxicity data do no t suggest that lime sulfur is acutely toxic to adult honey bees ( Apis mellifera ) which serve

, for assessment purposes, as a surrogate for beneficial terrestrial invertebrate s, t here are limited anecdotal reports of adverse effects to adult bees foraging in orchards during application of lime sulfur to orchards. This represents an uncertainty compared to laboratory

- based acute studies, but it could be mitigated by applying when bees are not active . Additionally, exposure to lime sulfur co uld be minimalize d if the compound is applied at times when bee foraging activity is reduced, i.e ., early morning or late evening. There is also s ome uncertainty regarding potential risk to terrestrial plant s given reported

incidents involving plants and its use as an apple blossom thinner

. Although lime sulfur can move from application sites to adjacent surface waters (both freshwater and estuarine/marine) via drift

from treated areas , the material is expected to rapidly dissociate into products that consist mainly

of sulfur and calcium ions, which are not believed likely to substantially alter natural background

levels of these elements in the environment. Consistent with the previous assessments and considering the rapid dissociation of lime sulfur

, EFED conclude s that there i s a low likelihood of

adverse effects to the environment from exposures resulting from the registered use of the compound as a fungicide /acaricide. Although there are data to indicate that lime sulfur is not acutely toxic to adult honey bees on a contact exposure basis, t here is uncertainty regarding the potential for adverse effects to non

- Apis terrestrial invertebrates and terrestrial plants following direct exposure.

1 USEPA. 2005. Reregistration Eligibility Decision for Inorganic Polysulfides List D. Case No. 4054. Office of Chemical Safe ty and Pollution Prevention formerly the Office of Prevention, Pesticides and Toxic Substances (7508C). Sept. 30, 2005. http://www.epa.gov/pesticides/reregistration/REDs/inorganic_polysulfides_red.pdf- Page 3 of 30

- 

# Ecological Risk Assessment for the Registration

Review of Lime Sulfur



# CaS

x

(x = 2, 3, 4, 5, 6, and 7; predominantly 5)



## Calcium Polysulfide (Lime Sulfur)

CAS Registry No : 1344

- 81

- 6 PC Code: 076702

Prepared by: Karen Milians, Ph.D., Chemist Andrew Sayer

, Ph.D., Biologist U.S. Environmental Protection Agency Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch IV 1200 Pennsylvania Ave., NW

Mail Code 7507P Washington, DC 20460 Reviewed by:

Jean Holmes

, DVM, MPH, Branch Chief Thomas Steeger, Ph.D., Senior Science Advis or Jim Carleton, Ph.D., Senior Scientist

February 25 , 201 6Page 4 of 30 

### Table of Contents

1. Executive Summary

................................ ................................ ................................ ............ 5

2. Problem Formulation

................................ ................................ ................................ .......... 6

2.1. Mode of Action

................................ ................................ ................................ ....... 6

2.2. Use a nd Usage Characterization

................................ ................................ ............. 6

2.4. Previous Risk Assessments

................................ ................................ ..................... 6

2.5. Water Quality

................................ ................................ ................................ .......... 7

2.6. Stressors of Concern

................................ ................................ ............................... 7

2.7. Conceptual Model

................................ ................................ ................................ ... 8

2.7.1. Risk Hypothesis

................................ ................................ ................................ ...... 8

2.8. Analysis plan

................................ ................................ ................................ ........... 8

2.8.1. Eco systems of Concern

................................ ................................ ........................... 8

2.8.2. Assessment and Measurement Endpoints

................................ ............................... 9

3. Exposure Characterization

................................ ................................ ................................ .. 9

3.1. Environmental Fate and Transport Summary

................................ ......................... 9

4. Ecological Effects Characterization

................................ ................................ .................. 11

4.1. Aquatic Organisms

................................ ................................ ................................ 11

4.1.1. Freshwater Fish

................................ ................................ ................................ ..... 12

4.1.2. Freshwater Invertebrates

................................ ................................ ....................... 12

4.1.3. Estuarine/Marine Fish

................................ ................................ ........................... 12

4.1.4. Estuarine/Marine Invertebrates

................................ ................................ ............. 12

4.1.5. Aquatic Plants and Algae

................................ ................................ ...................... 13

4.2. Terrestrial Organisms

................................ ................................ ............................ 13

4.2.1. Avian Taxa

................................ ................................ ................................ ............ 14

4.2.2. Terrestrial Invertebrates

................................ ................................ ........................ 14

4.2.3. Mammals

................................ ................................ ................................ ............... 14

4.2.4. Terrest rial Plants

................................ ................................ ................................ ... 15

5. Reported Ecological Incidents

................................ ................................ .......................... 16

6. Risk Characterization

................................ ................................ ................................ ........ 16

7. E ndocrine Disruptor Screening Program

................................ ................................ .......... 22

8. Endangered Species Assessments

................................ ................................ ..................... 22

9. Risk Conclusions

................................ ................................ ................................ .............. 24

10. Literature Cited

................................ ................................ ................................ ................. 25

11. Appendix A: The Sulfur Cycle

................................ ................................ ......................... 27

12. Appendix B: Output from OPP Aggregate Incident Database for Lime Sulfur

............... 30Page 5 of 30 1. Executive Summary

Calcium polysulfides, CaS
x (also called lime sulfur solution) have fungicidal and secondary acaricidal activity and are used to control powdery mildews, anthracnose, scab, spider mites and

other diseases on alfalfa, clover and fruits . The compound is also used to thin fruit in app le

orchards

. Lime sulfur is a n alkaline and corrosive solution containing 29

- 30% CaS
x ( where x = 2, 3, 4, 5, 6, and 7 ) as the active ingredient (a.i) , with the predominant form being the pen t a sulfide (pH 11.5

- 11.8) . In addition, minor amounts of calcium thiosulfate (CaS 2 O 3 ), calcium sulfite (CaSO 3 ), sulfur (S), and gypsum ( CaSO 4 ·2H 2 O ) may be present. The calcium polysulfides rapidly dissociate in the presence of moisture to form calciu m cations and anionic and elemental

sulfur. Given the anticipated rapid dissociation of calcium polysulfides into constituent ions on

introduction to water

, c alcium polysulfides are not expected to accumulate in surface water, or to accumulate on forage sources in the terrestrial environment. Therefore, there is a low likelihood

of c hronic exposure for aquatic and terrestrial organisms.

While toxicity tests indicate that the compound ranges from highly to moderately toxic to aquatic animals, adverse effects may in large part be based on direct mixing of the active in gredient in water with poor buffering capacity in laboratory

- based studies and may not be reflective of actual exposure conditions under which the compound is expect to rapidly dissociate. For terrestrial organism s , lime sulfur is slightly to practically non

- toxic to birds (reptiles and terrestrial

- phase amphibians), moderately toxic to mammals

, and practically non

- toxic to terrestrial invertebrates

on an acute basis

.

Although r isk estimates exceed the level of concern (LOC) for federally listed threate ned and endangered ( listed) and non

- listed species of aquatic and terrestrial animals on an acute exposure
basis , the likelihood of adverse effects from exposure to lime sulfur is considered low given rapid dissociation of calcium polysulfide to co nstituents with very low toxicity under typical

environmental conditions

. Similarly, the likelihood of chronic exposure to the compound and

hence risk is considered low. Although lime sulfur is practically non

- toxic to honey bees ( Apis mellifera ) on an ac ute contact exposure basis

, there is some anecdotal information that bees may be adversely affected if application s are made while bees are actively foraging; the likelihood of an adverse effects could be reduced though by applying at times when honey bee foraging activity is low. Larvae of other beneficial insects may be affected at maximum application rates; however, the instability of the compound under most environmental conditions may limit the extent to which

this occurs.

Terrestrial plant data ar e not available, but adverse effects on terrestrial plants have been reported following applications of lime sulfur

. Also its use as an apple blossom thinner indicate adverse effects on terrestrial plants. To the extent that lime sulfur adversely affects plants, there can be

adverse secondary effects to organisms that depend on those plants for forage and habitat

. Given

the uncertainty regarding poten tial risk to terrestrial plants. T errestrial plant toxicity data would

reduce th is uncertainty.Page 6 of 30 2. Prob lem Formulation

2.1. Mode of Action

Calcium polysulfides (CaS
x or lime sulfur) are inorganic pesticides applied to some agricultural

crops as a fungicid e and /or acaracide

. Lime sulfur has been used for over 100 years as a contact fungicide/acaricide to control powdery mildews, anthracnose, scab, spider mites and other diseases on alfalfa, beans, clover and fruits (Tomlin 1994). The mode of action of calcium polysulfides is

unkn own; however, g iven the rapid dissociation of calcium polysulfides in wate r
, chronic exposure of aquatic and terrestrial ecosystems to parent calcium polysulfides is not expected.

2.2. Use and Usage Characterization

Labelled Use Based on current labels, lime sulfur is registered for feed and food uses on the following crops: alfalfa, almonds, apples, blackberries, blueberries, boysenberries, caneberries, cherries (sweet), cherries (tart), citrus, clover, currants, deciduous fruit trees, gooseberries, grapes, hazelnuts, nectarines, oranges, peaches, pears, pecans, pistachio nuts, plums, prunes, quinces, raspberries, rye, stone fruits, tangerines, and walnuts. G roupings of major crop uses were based on the maximum application rates. Other factors were also considered in cluding application method, total acreage of bearing crops that may be treated, and total pounds of lime sulfur applied per year. A complete list of these uses and application parameters are included in the 2005 RED and 2015

new use document s

.

Usage

Based on available pesticide usage information for the years 2004 through 2013

, the Screening

Level Uses Analysis of Calcium Polysulfide ( SLUA ; EPA 20 1 5) provides average annual

estimates of lime sulfur usage for several crops. The SL UA indicates the greatest usage occurred on apples

, grapes and pears with on average 900 ,000 pounds

, 500 ,000 and 300,000 pounds of active ingredient ( lbs. a.i.), respectively , applied annually

.

2.4. Previous Risk Assessments

The most recent assessment of lime sulfur was conducted in 2015 ( D422723 ; USEPA 2015 )

, and a previous risk assessment of calcium polysulfides was conducted in 2005

. B oth assessments have similar conclusions ( D313165 , USEPA 2005) ; g iven the rapid dissociation of calcium polysulfides

in water

, chronic exposure of aquatic and terrestrial ecosystems to parent calcium polysulfides is not expected. Therefore, the chronic toxicity guideline studies have previously been waived. Risk

conclusions from the 2005 RED and the 2015 new use assessment are a s follows:

• listed freshwater fish (as well as aquatic

- phase amphibians) are at acute risk from drift ;

• acute risk exists to listed and non

- listed birds (as well as terrestrial

- phase amphibians and reptiles) ;

• acute risk exists to listed and non

- listed m ammals ; and,

• in the absence of terrestrial plant toxicity data, r isk may occur to listed and non

- listed

sulfur

- sensitive terrestrial plantsPage 7 of 30 The 2005 RED assessment of calcium polysulfides also noted that lime sulfur readily transform s to calcium hydroxide , Ca(OH) 2 and elemental sulfur and that calcium hydroxide is a food additive

and is generally recognized as safe (GRAS) by the U

. S

. Food and Drug Administration (FDA). According to the sulfur RED, " The human risks, if any, from both dietary and occupation al exposures are considered to be very low because of the general knowledge of the chemical sulfur, its ubiquitous occurrence, and its low toxicity, as well as its long history of use by humans, including some pharmaceutical applications ." However, sulfur can cause eye and skin irritation

and EPA has identified the potential hazard for workers re

- entering fields following foliar application of lime sulfur dust ( i.e ., eye and skin irritation to people who handle the dust or who

come into contact with treated foliage during field work).

Although the previous ecological assessment identified acute risks for freshwater fish resulting from spray drift and acute risks for birds and mammals due to direct application bas ed on laboratory studies, because of the rapid dissociation of calcium polysulfide to co nstituents with very low toxicity under environmentally realistic conditions

, no measures to mitigate potential

risks to freshwater fish, mammals

, or avian species are warranted at this time.

2.5. Water Quali ty

Lime sulfur is not identified as a cause of impairment for any water bodies under section 303(d)

of the Clean Water Act 2 ( accessed S eptember 10, 2014) . In addition, no Total Maximum Daily Loads (TMDLs) have been developed for lime sulfur and there are no aquatic life criteria for lime

sulfur 3

.

2. 6. Stressors of Concern

Calcium polysulfides are produced by reacting calcium oxide (CaO; qu i c k lime ) or calcium hydroxide (Ca(OH) 2 ; slaked lime) with sulfur to produc e a highly alkaline solution (pH 11.5

- 11.8) and corrosive product

, i.e ., CaS
x 4 . When released into the moisture

- rich compartments of the environment, lime sulfur is expected to transform (dissociate) quickly into polysulfide anions (which in turn is quickly converted to sulfur in var ious forms “S” ) and calcium cations (Ca 2+ )

. Elemental anionic s ulfur and calcium cations are ubiquitous in the environment and the amounts of calcium and sulfur incorporated into the ecosystem from the use of calcium polysulfides are considered negligible. Therefore, only the parent compound (undissociated form of CaS
x 5 ) i s the

s tressor of concern.

2 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885

3 http://www.epa.gov/waterscience/criteria/aqlife/index.html

4 T he registrant submitted information on the product chemistry of the pesticide (MRID 43894401) and on its chemical identity (MRID 41769502). Both submissions are not guideline studies.

5 The registrant submitted information on the product chemistry of the p esticide (MRID 43894401) and on its chemical identity (MRID 41769502). Both submissions are not guideline studies.Page 8 of 30 2.7. Conceptual Model

For a pesticide to pose an ecological risk, it must reach ecological receptors in biologically significant concentrations. An exposure pathway is the means by which a pesticide moves in the environment from a source to an ecological receptor. For an ecological pathway to be complete, it must have a source, a release mechanism, an environmental transport medium, a point of exposure for ec ological receptors, and a feasible route of exposure.

The conceptual model for lime sulfur provides a written description of the predicted relationships between the potential routes of exposure to lime sulfur and the predicted effects for the assessment

e ndpoint (USEPA 1998).

As discussed previously, several ecological risk assessments have been conducted by EFED for lime sulfur, including a national level risk assessment supporting the reregistration eligibility decision (USEPA 2005).

2.7.1

. Risk Hypothesis

A risk hypothesis describes the predicted relationship among the stressor, exposure, and assessment endpoint response along with the rational e for their selection. For lime sulfur , the following ecological risk hypothesis is b eing employed for this PRA :

Based on the most sensitive toxicity values, direct exposure to calcium polysulfides from their use as a fungicide/acracide may result in acute and chronic adverse effects to non

- target aquatic (freshwater fish) and terrestrial (birds and mammals) organisms as a result of the registered use of the compound. Acute adverse effects to non

- target terrestrial plants and beneficial insects are also possible.

2. 8

. Analysis plan

2.8.1

. Ecosystems of Concern

Aquatic Environment

The environmental fate properties and use patterns of lime sulfur indicate that the compound dissociates rapidly and is not likely to move directly into su rface water except as spray drift; however, exposure of aquatic ecosystems through spray drift is likely to be reduced through the large volume and natural buffering capacity of most receiving water s as well as oil formulations

of lime sulfur which limit t he extent to which drift may occur

. However, w hile direct exposure to

lime sulfur can result in acute adverse effects on aquatic ecosystems in poorly buffered systems

, the rapid dissociation of the compound in water is expected to reduce the likelihood of such effects.

The likelihood of chronic adverse effects on aquatic ecosystems is considered low given the rapid

dissociation of the compound.

Terrestrial EnvironmentPage 9 of 30 Exposure of terrestrial vertebrates ( e.g ., birds, mammals, reptiles, terrestrial

- phase amphibians) and invertebrates ( e.g ., insects ), and terrestrial plants to lime sulfur from direct spray drift from labeled use of the pesticide may cause reduced survival, growth

, and reproduction to terrestrial

invertebrates. T errestrial organisms may be subject to acute exposure to the parent compound

fr o m direct contact on

- site or through dri ft to adjacent areas , however, si milar to aquatic environments, lime sulfur is expected to rapid ly dissociat e in terrestrial environments to its non

toxic constituent (elemental forms of calcium and sulfur) that do not substantially alter natural background levels of these compounds

. In a worst case scenario, the application of lime sulfur on the terrestrial environment at the highest application rate will lower (acidify) acidic or neutral soils by less than 0.5 pH units. This is further discussed in Section 6.

2.8.2

. Assessment and Measurement Endpoints

Assessment endpoints represent the actual environmental value that is to be protected, defined by

an e cological entity (species, community, or other entity) and its attr ibute or characteristics (USEPA 1998). For lime sulfur , the ecological entities include the following: birds, amphibians, reptiles, mammals, freshwater fish and invertebrates, estuarine/m arine fish and invertebrates, terrestrial plants, insects, and aquatic plants and algae. The attributes assessed for each of these entities may include growth, survival, and reproduction. The assessment endpoints are intended to reflect population sustai nability and community structure within ecosystems and hence relate back to ecosystems at risk. If risks are expected for given species/taxa based on the screening

level assessment, then risks might be expected to translate to higher levels of biological organization.

Measurement endpoints are standardized so that acute toxicity is represented by levels that result in mortality to 50% of tested individuals ( i.e., LC 50 , LD 50 and EC 50 ) and chronic toxicity is represented as a no observed adverse effect concentration or level ( i.e., NOAEC or NOAEL).

Tables 1 and 2 include the most sensitive toxicity endpoints available for lime sulfur that will be

used to assess risks to terrestrial and aquatic organisms.

3. Exposure Characterization

3.1. Environmental Fate and Transport Summary

The environmental fate of lime sulfur was previously evaluated ( in 2005 ) to support the RED for inorganic polysulfides 6 and was more recently assessed to support a new use of lime sulfur to thin fruit in apple orchards (USEPA

, 2015). Since publication of the 2005 RED, no additional environmental fate data have been provided to EPA.

6 USEPA. 2005. Reregistration Eligibility Decision for Inorganic Polysulfides List D. Case No. 4054. Office of Chemical Safe ty and Pollution Prevention formerly the Office of Prevention, Pesticides and Toxic Substances (7508C). Sept. 30, 2005. http://www.epa.gov/pesticides/reregistration/REDs/inorganic_polysulfides_red.pdfPage 10 of 30 As noted in the 2005 RED, calcium poly sulfides dissociate in water into calcium cations and polysulfide anions (which in turn transform into sulfur in various forms), and therefore the fate of this pesticide in the aqueous environment is dependent on the fate of its dissociation products. In this respect, two important factors are considered: the first is the expected change in environmental background levels of calcium ions and sulfur due to application of the pesticide ; and

, the second is the fate and transport of these dissociation products

.

W ith respect to changes in the environment due to applications of lime sulfur

, the use pattern s and/or application rates of lime sulfur are not expected to increase the total calcium or sulfur

content of soils above typical background levels.

In considering the second factor, the RED noted that both calcium ions and sulfur react with other substances found in the environment, forming various calcium

- and sulfur

- containing compounds. Sulfur in its elemental form is relatively immobile, as it is hi ghly insoluble and largely precipitates

out of solution. Other forms such as thiosulfate may remain in solution and form complexes with metals commonly found in the natural environment. The fate of sulfur is dependent upon the

characteristics of the enviro nment in which it is found ( i.e

., soil, water/sediment or surface water), and is largely determined by the oxidation/reduction potential of the system and the type of microorganisms present (refer to the sulfur cycle in Appendix A ). Under oxidizing condit ions ( e.g ., in aerobic soils or surface water ) elemental sulfur is oxidized to sulfate by autotrophic bacteria. Under sufficiently low oxidizing conditions ( e.g ., in anaerobic soil/sediments) sulfate is reduced to sulfide, which may be found in forms incl uding hydrogen sulfide (H 2 S), bisulfide (HS

1 ), and free sulfide anion (S

- 2 ).

Hydrogen sulfide is a weak acid, while bisulfide and free sulfide are strong bases; the relative proportions of these three chemical entities will thus largely be governed by the pH of the medium. Sulfide may react with iron and other transition metals to form insoluble precipitates. Hydrogen

sulfide itself is somewhat volatile and may evaporate to some extent. The 2005 RED concluded that it is unlikely that elevated levels of hydrogen sulfide will form in the environment as a result

of the agricultural use of calcium polysulfides because the amount of sulfur a dded into the sulfur cycle from usage of these products is unlikely to substantially contribute to the pool of sulfur already present in reducing environments.

Calcium polysulfides are produced by reacting lime with sulfur in boiling water resulting in a concentrated alkaline solution (pH 11.5

- 11.8). Application of calcium sulfides to targeted foliage/soils and its movement to water bodies by drift results in low concentrations of calcium polysulfides in these systems. Such quantities are not believed likely to significantly alter natural background levels of these elements in the environment nor are they expected to substantially alter the pH of receiving waters because of natural buffering capacity typically present. Such additions might potentially cause small increases in the pH of a water body that has low buffering capacity; however, minor fluctuations in pH are not expected to have direct impact on the aquatic life

contained therein. Refer to Appendix A where an analysis of the contribution from spray drift alone in a low buffering capacity environment was simulated in soil and aqueous environment. The results of that analysis indicate that when using the maximum annual application rate of lime sulfur, spray drift will not significantly change the pH of the aquatic environment and therefore, is11 not expected to adversely impact aquatic life. Similarly, when lime sulfur is applied at the maximum application rate to soils with low buffering capacity, the pH in soil will not be impacted significantly.

The fate of lime sulfur depends on the fate of its dissociation products: calcium and sulfur. Calcium cations can be found naturally in the environment and are not expected to cause an adverse effect by their release. A fter application, polysulfides enter the sulfur cycle. The main processes and dissipation of elemental sulfur are oxidation to sulfate ( SO 4 2

- ; produced in soils under aerobic

conditions when bacteria are growing ) and reduction to sulfide (S 2

- ; under anaero bic conditions).

Both of t hese processes are mainly mediated by microbes. The dissipation of SO 4 2

- is dependent on leaching and soil organic matter immobilization (USEPA, 2013) . The fate of S 2

- is dependent on metal sulfide precipitation or volatilizati on of H 2 S. The oxidation of sulfur leads to formation

of sulfuric acid. The sulfuric acid will dissociate to form hydrogen ions and sulfate ion (SO 4 - 2 )

, which may decrease the pH of some soils and shallow water bodies

.

The oxidation reaction that occurs is as follows

, wherein hydrogen ions ( H + ) are liberated into the soil environment, potentially decreas ing soil pH:

CO

2 + S 0 + 1⁄2O

2 + 2H

2 O → CH

2 O + SO

4 2

- + 2 H +

S ulfate ion s may inte ract with calcium (Ca 2+ ) and magnesium ions (Mg 2+ ) in water to form sulfate (SO 4 ) salts. H ydrogen ion s will generally be neutralized by the carbonate buffering system

.

Calcium ions react with carbonate ions to form calcium carbonate. The dissolved carbonate ion acts as a base and produce s bicarbonate ion and hydroxide ion in the water (Baird, 2003).

Ca 2+ + CO 3 - 2   CaCO 3 CaCO 3 + H 2 O   Ca 2+ + HCO 3 - + OH

Elementa l sulfur, in fact, is used as an amendment to supplement soil fertility a nd it i s utilized on crops as a fungicide/ acaracid e (EPA Reg. No. 2935

- 407, PC code 077501 )

.

Considering the previously

- recognized rapid dissociation of calcium polysulfide

, and that no additional data have been identified to alter and/or contradict the previous assessments, EPA’s understanding of the environ mental fate of lime sulfur has not changed.

4. Ecological Effects Characterization

A detailed description of the available ecotoxicity data for lime sulfur is provided in the Environmental Fate and Ecological Risk Assessment written in support of the RED f o r c alcium

p olysulfides (USEPA 2005). Since the completion of that assessment, no new ecological effect s data on lime sulfur ha ve been submitted to the EPA

.

4.1. Aquatic Organisms12 Lime sulfur is categorized as highly toxic to freshwater fish and is moderately toxic to freshwater invertebrates on an acute exposure basis. Since freshwater fish serve as surrogates for aquatic

phase amphibians, lime sulfur is categorized as highly toxi c to this taxon as well. No data are available to assess the toxicity of lime sulfur to estuarine/marine animals. E xposure to lime sulfur altered the pH and dissolved oxygen content of the test water and resulted in decreased number of eggs hatched in be nthic aquatic invertebrates. In a worst case scenario, the application of lime sulfur on the terrestrial environment at the highest application rate will lower (acidify) poorly

buffered aquatic habitats (such as a pond) by less than 0. 5 pH units. This is further discussed in

Section 6. Given the rapid dissociation of lime sulfur, chronic toxicity studies have been waived. An overview of submitted aquatic organism studies can be seen in Table 1

.

4.1

. 1. Freshwater Fish

The acute toxicity of lime sulfur ( calcium polysulfides) formulation (29% active ingredient) was evaluated in the freshwater rainbow trout ( Oncorhynchus mykiss ; McCann 1976), fathead minnow ( Pimphales promelas ; MRID 40098001), and bluegill sunfish ( Lepomis macrochirus ; MRID 40098001). The most sensitive freshwater fish tested was the rainbow trout with a 96

- hour LC 50 value of 0.97 mg a.i./L. Based on this information, lime sulfur is categorized as highly toxic to
freshwater fish on an acute exposure basis. Toxicity data are not available for aquatic vascular plants; however, exposure of the nonvascular green algae to lime sulfur resulted in a 120

- hr EC 50 of 14.1 mg/L.

4.1

. 2. Freshwater Invertebrates

The acute toxicity of lime sulfur formulation (29% a.i.) was evaluated in two species of invertebrates, i.e

., water flea s
, Daphnia pulex (MRID 40098001) and Simocephalus serrulatus (MRID 40098001), with reported 48

- hour LC 50 values of 2.9 mg a.i./L and 3.2 mg a.i./L, respectively. Based on these results, lime sulfur (calcium polysulfides) is categorized as moderately toxic to freshwater invertebrates on an acute exposure basis

.

The effects of acute exposure (72 hours) of lime sulfur (calcium polysulfides) was examined on egg hatchability in the midge ( Chironomus riparius ), a freshwater benthic invertebrate

. Results of this study demonstrate a dose

- dependent decrease in egg hatchability, with an estimated NOAEC of 3.2 mg/L ( Wegner and Hamilton 1976) . Due to several confounding factors, including

concentration

- dependent increa se in pH and decrease in dissolved oxygen, results are not suitable for quantitative use in risk assessment.

4.1

. 3. Estuarine/Marine Fish

No data are available to assess the acute toxicity of lime sulfur to estuarine/marine fish.

4.1

. 4. Estuarine/Marine Invertebrates

No data are available to assess the acute toxicity of lime sulfur to estuarine/marine invertebrates.

Chronic Effects13 EFED waived the data requirements for chronic toxicity studies of aquatic organisms due to the rapid dissociation of lime sulfur in the environment and low likelihood of chronic exposure

.

4.1

. 5. Aquatic Plants and Algae

The toxicity of lime sulfur was evaluated in the nonvascular aquatic green algae ( Pseudokirchneriella subcapitata formerly Sel e nastrum capricornutum ; M RID 43960801). Results of this study showed 120

- hour EC 05 and EC 50 values of 0.5 mg a.i./L and 14.1 mg a.i./L

, respectively.

No further information is available regarding the potential effects of lime sulfur exposure to aquatic

vascular or nonvascular plants

.

Table 1 : Lime Sulfur Acute Toxicity Values for Aquatic Animals

.

4.2. Terrestrial Organisms

Lime sulfur is categorized as slightly toxic to birds on an acute oral exposure basis and as practically nontoxic to birds on a subacute dietary exposure basis; the compound is categorized as moderately toxic to mammals on an acute oral exposure basis. Since birds serve as surrogates for reptiles and terrestria l

- phase amphibians, the same toxicity classification applies to these taxa. While lime sulfur is practically non

- toxic to honey bees on an acute contact exposure basis, Species Lime Sulfur

(Calcium Polysulfides)

Toxicity Value in mg/L

(MRID) Test Material

Rainbow trout ( Oncorhynchus mykiss ) 96

- hour LC 50 =0.97

(McCann 1976) a 29% formulation (Miller Lime Sulfur Solution)

96

- hour LC 50 =2.4

(40098001) a 29% formulation

Bluegill sunfish

( Lepomis macrochirus ) 96

- hour LC 50 = 14.1

( 40098001 ) a 29% formulation

Fathead minnow

( Pimephales promelas ) 96

- hour LC 50 = 9.2

( 40098001 ) a 29% formulation

Waterflea

( Daphnia pulex ) 48

- hour LC 50 =2.9 (40098001 ) a 29% formulation

Waterflea ( Simocephalus serrulatus ) 48

- hour LC 50 =3.2 (40098001 ) a 29% formulation

a Study report did not specify if toxicity endpoints were expressed in terms of mg formulation/L or mg a.i./L.14 exposure to other insects resulted in mortality at application rates below current maxi ma. Given the rapid dissociation of lime sulfur, chronic toxicity studies have been waived. No data are available to assess the toxicity of lime sulfur to terrestrial plants. An overview of submitted

terrestrial organism studies can be seen in Table 2

.

4 .2. 1. Avian Taxa

The acute oral exposure of bobwhite quail ( Colinus virginianus ) to lime sulfur resulted in an LD 50 value of 560 mg a.i./kg bw (MRID 43945101). Based on this study, lime sulfur is classifie d as slightly toxic to birds (and to reptiles and terrestrial

- phase amphibians for which birds serve as surrogates) on an acute oral exposure basis. T reatment

- related clinical signs and gross patholog y in the acute oral toxicity study in bobwhite quail included ataxia, hyporeactivity, immobility, crop damage, gastric ulcers and hemorrhaging (location not specified).

The sub acute dietary toxicity of lime sulfur was evaluated in bobwhite quail (MRID 43945103) and mallard ducks ( Anas platyrhynchus ; MRID 43945104). Both studies yielded LC 50 values >5,000 mg a.i./kg diet. Based on these results, lime sulfur is categorized as practically non

- toxic

to birds on a sub acute dietary exposure basis. No clinical s igns or gross patholog y were observed

in the sub acute dietary studies in bobwhite quail and mallard ducks.

4.2. 2. Terrestrial Invertebrates

The acute contact laboratory

- based study of honey bees with lime sulfur resulted in a 48

- hr. LD 50 >25 μg a.i./bee (MRID 43945102); therefore, lime sulfur is classified as practically non

- toxic to

adult honey bees on an acute contact exposure basis. However, t here are limited anecdotal reports

of adverse effects to adult bees foraging in orchards during application o f lime sulfur to orchards ; however, these reports are not consistent with the laboratory

- based acute toxicity data. This represents an uncertainty

.

In addition to the acute contact study in honey bees, the acute toxicity of formulated calcium polysulfides to non

- target beneficial insects has been reported in the open literature . These studies

have inc luded parasitic wasps ( e.g ., Aphytis lophanthae ) (Bartlett 1966; 1973), predator y beetle s ( e.g ., Cryptolaemus montrouzieri ; Bartlett 1966; 1973) and predatory mites ( e.g ., Typhlodromus doreenae) (Bartlett 1964; James and Rayner 1995). Results show that exposure to calcium polysulfides at levels consistent with label

- recommended rate s does result in mortality of these

non

- target beneficial insects unde r the conditions tested

.

4.2. 3. Mammals

In an acute oral toxicity study with Sprague

- Dawley rats ( Rattus norvegicus ) administered single doses of a calcium polysulfides formulation

, the acute LD 50 values for male and female rats

were 11 9 mg a.i./kg bw and 86.6 mg a.i./kg bw , respectively ( Accession No. 00154738). Based on these result, lime sulfur is classified as moderately toxic to mammals on an acute oral exposure basis. However, treatment

- related sublethal effects were reported in this study and included ataxia, convulsions, lethargy, morbidity , diarrhea, and weight loss. Gross patholog y findings included enlarged adrenal glands, discolored liver, and dark red lungs, kidney s , and spleen.15 Chronic Effects

D ata for chronic toxicity studies to t errestrial organisms are not required due to the rapid

dissociation of lime sulfur in the environment and an incomplete ch r o nic exposure pathway

.

4.2.4. Terrestrial Plants

No data have been submitted to the EPA to characterize risks from application of lime sulfur to terrestrial plants. Based on the use of lime sulfur to thin apple blossom s along with incident reports, lime sulfur can affect abscission in plants and may have the capacity for non

- target phytotoxicity.

Table 2 : Lime Sulfur Acute Toxici ty Values for Terrestrial Animals

.
Exposure

Scenario Species Test Material Toxicity Reference Value Reference MRID (Classification)

Mammals

Acute (Dose

based) R at Orthix Spray (aqueous product containing 16.66% a.i.) LD 50 = 86.63 mg a.i./bw

. a

( single oral dose ) Accession No.

00154738 (Acceptable)

Birds

Acute (Dose

based) B obwhite quail

( Colinus virginianus ) 29%

formulation LD 50 = 560 mg a.i./kg bw

( single oral dose ) 43945101 (Acceptable)

Acute (Dietary

based) Bobwhite

q uail ( Colinus virginianus )

and

M allard duck

( Anas platyrhynchus ) 29 %

formulation LC 50 >5000 mg a.i./kg diet (for both species)

( 5

- day dietary ) 43945103 quail (Acceptable)

43945104 duck

(Acceptable)

Terrestrial invertebrates

Acute contact Honey bee

( Apis mellifera ) 29%

formulation LD50 > 25 ug a.i./bee ( single contact dose ) 43945102 (Acceptable)

a The study report did not specify if toxicity endpoints were expressed in terms of mg formulation/L or mg a.i./L.16 5. Reported Ecological Incidents

The ecological incident information system (EIIS) is a database maintained by the Office of Pesticide Programs; the database contains ecological incidents that have been reported to the EPA

. When available, EIIS includes date and location of an incident, type and magnitude of effects observed in various species, use(s) of pesticides known or suspected of contributing to the incident, and results of any chemical residue analysis or other analyses conducted during incident investigation. EIIS incidents are categorized according to the certainty that the incident resulted from pesticide exposure. The Avian Incident Monitoring System (AIMS) is a database administered by the American Bird Conservancy that contains publicly available data on reported

avian inci dents involving pesticides. Many of the incidents listed in this database are also in the EIIS. Because of uncertainties regarding the extent to which incidents are reported to EPA, the absence of incident reports cannot be construed as the absence of in cidents. This database was

searched in December 2014 and returned no incidents related to the use of lime sulfur.

Based on the 40 CFR §159.184, information on all known “major” incidents must be submitted to

the EPA by the registrant(s). EIIS contained one incident for lime sulfur. The incident, which took place in Illinois and was reported in March 2001, caused plant damage on 160 acres of directly

treated corn and was listed as “possibly” caused by lime sulfur (based on the certainty index). It

was u ndetermined if the incident was due to a misuse of the product.

All ecological incidents considered “minor” only need to be aggregately reported in Aggregate Incident Reports (AIR) as quarterly counts of incidents by the registrant(s). The incidents list ed in this database may also appear in the EIIS. From the AIR, a total of six minor incidences were reported between April 1995 and June 2012 ( Appendix B ). All of these incidences involved minor plant damage ; however it is uncertain whether these incident s occurred as a result of a direct application to the affected plants at registered rates

. Because of uncertainties regarding the extent to which incidents are reported to EPA, the absence of incident reports cannot be construed as the

absence of incident s.

6. Risk Characterization

Risk characterization is the integration of exposure and effects characterization to determine the ecological risk from the use of calcium polysulfides and the likelihood of effects on aquatic life and wildlife based on varying pesticide

- use scenarios. The ri sk characterization articulates risk assessment assumptions, limitations, and uncertainties

. N o new data ha ve been submitted or reviewed by the EPA

.

As stated in the 2005 RED , calcium polysulfides are assumed to react quickly in the environment; runoff and/or leaching of the intact parent compound into nearby water bodies is assumed to be negligible. Therefore, estimates of calcium polysulfides for aquatic ecosystems were based o n drift alone using the model AGDRIFT. AGDRIFT estimates the fraction of pesticide that is

re leased indirectly to a water body due to spray drift following a typical aerial or ground based application to a crop. Drift alone was considered since the likelihood of runoff of the intact17 material f rom treatment zones is low given the rapid dissociation of the material. Application rates ranging from approximately 3 lbs a.i./A (alfalfa) to 6 7 lbs a.i./A (blueberries and grapes) were employed to estimate the fraction of spray drift and loading of c alcium polysulfides to a water body downwind from the release site. Initial concentrations of parent calcium polysulfides, in surface water ranged from less than 0.7 micrograms per liter (μg a.i./L) to approximately 120 μg a.i./L , depending upon the appli cation rate and method. Although monitoring data do not exist for calcium polysulfides in natural waters, background levels of its dissociation products of sulfur and

calciu m are usually in the milligram per liter (mg/L) range. Estimated concentrations o f the dissociation products from the maximum estimated concentration of calcium polysulfides (the 12 μg a.i./L ) results in a maximum “Ca + ” content of 24 μg a.i./L and a maximum sulfur “S

- ” content

of 96 μg a.i./L 7 being added to water bodies due to spray drift loading and are well below the ambient levels of these compounds in natural waters

.

In the biosphere , sulfur produced from calcium polysulfides becomes incorporated into the global sulfur cycle ( see Appendix A ) and its fate in the environment is dependent upon the oxidation/reduction potential of the soil, sediment or water system

, and the type of microorganisms

present.

The EFED terrestrial exposure model T

- REX was used to estimate exposures and risks to av ian and mammalian species for single spray applications of calcium polysulf ides at rates ranging from approximately 3 lbs a.i./A (alfalfa) to 67 lbs a.i./A (blueberries and grapes). The model provides estimates of exposure concentrations and calculates ri sk quotients (RQs) for three body weight

classes each for birds and ma mmals. In the calculation, the model uses chemical residues on the surface of different types of foliage that may be sources of exposure to avian, mammalian, reptilian, or terrestrial

- ph ase amphibian receptors. Maximum residues of calcium polysulfides ranged from 46 mg a.i./kg diet for fruits/pods/large insects from application to alfalfa to 15,979 mg a.i./kg diet for short grass from application to blueberries. However, these exposure estimates do not consider the extent to which the compound is subject to rapid dissociation.

Toxicity data and exposure estimates for lime sulfur are used to evaluate the potential for adverse ecological effects on non

- target species. This screening

- leve l assessment employs a deterministic risk estimation method, based on RQ values, to provi de a metric of potential risks . The potential for risk is based on the risk estimation results and other relevant information about toxicity and ecosystems potentiall y at risk, and the environmental fate and transport characteristics of lime

sulfur . U nitless RQ value s are compared to the EPA ’s LOCs to identify taxonomic groups potentially at risk of acute or chronic effects associated with lime sulfur’s registered uses.

For a complete overview of the risk estimation and risk characterization, refer to the 2005 RED.

Tables 3 through 6 , taken from the 2005 RED, are presented below. Briefly, acute RQ values

exceed LOCs for acute risk to aquatic and terrestrial animals . The highest exceedances are

associated with the highest application rate ( i.e.

, blueberries; 66.58 lbs a

. i

. /A) and lowest for alfa lfa

7 Calculation is based on an assumption that the compound is 100% CaS 5 that is 80% “S” plus 20% o “Ca + ions” (Based on a molecular weight conversion).18 (3.07 lbs a

. i

. /A) for e ach of the crop group ings assessed . The 2015 new use assessment (D422723)

evaluated the proposed use of lime sulfur to thin fruit in apple orchard s ; the blueberry application

rate modelled below is similar to the maximum rate us ed to thin apples ( i.e

., 66.58 and 71.28 lbs

a

. i

. /A for blueberries and apples, respectively).

T able 3

. Acute RQs for Freshwater Fish and Freshwater Invertebrates Exposed to Calcium Polysulfides Based on Maximum Application Rates

Crop Use (Application Rate) Application Type EEC (mg a.i./L) Acute RQ a

Freshwater Fish Freshwater

Invertebrate

Blueberries (66.58 lb a.i./A) Aerial 0.11971 0.12 b 0.041

Grapes (61.48 lb a.i./A) Aerial 0.11054 0.11 b 0.038

Air blast 0.000651 0.0007 0.00022

Almonds (49.18 lb a.i./A) Aerial 0.08843 0.091 b 0.030

Apples (33.81 lb a.i./A) Aerial 0.06079 0.063 b 0.021

Alfalfa (3.07 lb a.i./A) Aerial 0.00553 0.0057 0.0019

a RQs = EEC/LC 50 , where EECs are the peak concentrations in surface water generated from AGDRIFT, and acute toxicity reference values are as follows: freshwater fish, rainbow trout 96

- hr LC 50 = 0.97 mg a.i./L; freshwater invertebrates, waterflea 48

- hr EC 50 = 2.9 mg a.i./L.

b RQs exceed LOC for acut e risk to listed species (LOC 0.05).

Although Table 3 indicates that acute risk LOCs are exceeded for listed fish based on estimated environmental concentrations in water, l ime sulfur is not directly applied to water ; t herefore, its potential movement into surface water would be limited to drift. Current oil formulations would

reduce the amount of lime sulfur available to reach water bodies via drift and the analysis of drift

discussed earlier indicates that neither background levels of calcium and sulfur nor pH would likely be substantially affected

. L ime sulfur applied in the terrestrial environment is expected to degrade into its constituent elements , the addition of which to soil is not expected to cause significant deviations from background or ambient levels of calcium and sulfur . During a runoff

even t ( i.e.

, overland flow of water following a period of precipitation ) , negligible amounts of lime

sulfur would be expected to enter a water body

, due to the rapid dissociation of the compound in

soi ls

. Therefore, the likelihood of adverse effects on fish and aquatic

- phase amphibians from the

use of lime sulfur is considered low due to the low likelihood of exposure

. Although no data are available to assess the potential toxicity of lime sulfur to es tuarine/marine organisms, similar to freshwater organisms, the likelihood of exposure is considered low.

Table 4

. RQs for Listed and Non

- Listed Aquatic Non

- vascular Plants Exposed to Calcium Polysulfides

Crop Use (Application Rate) Application Type EEC (mg a.i./L) RQ a

Non

- Listed Aquatic Algae Listed Aquatic Algae

Blueberries (66.58 lb a.i./A) Aerial 0.11971 0.00849 0.219 Crop Use (Application Rate) Application Type EEC (mg a.i./L) RQ a

Non

- Listed Aquatic Algae Listed Aquatic Algae

Grapes (61.48 lb a.i./A) Aerial 0.11054 < 0.0 1 0.2

Air blast 0.000651 < 0.0 1 < 0.0 1

Almonds (49.18 lb a.i./A) Aerial 0.08843 < 0.0 1 0.2

Apples (33.81 lb a.i./A) Aerial 0.06079 < 0.0 1 0.1

Alfalfa (3.0 lb a.i./A) Aerial 0.00553 < 0.0 1 0.01

a RQs = EEC/LC 50 , where EECs are the peak concentrations in surface water generated from AGDRIFT, and acute toxicity

reference values are as follows for the nonvascular aquatic plant Pseudokirchneriella subcapitata: non

- listed species 120

- hour

EC 50 =14.1 mg a.i./L; listed algae 120

- hour EC 05 =0.5 mg a.i./L

Laboratory

- based studies indicate that lime sulf ur is slightly toxic to birds on an acute oral exposure basis; however, the compound is practically non

- toxic to birds ( and terrestrial

- phase amphibians and reptiles) on a subacute dietary exposure basis. While the acute oral toxicity test

was conducted a ccording to guideline specifications, the likelihood that birds (and terrestrial

- phase amphibians and reptiles) would voluntarily consume a caustic solution is considered low; therefore, the subacute dietary toxicity test is considered to be a more realist ic indicator of toxicity to lime sulfur residues on dietary forage items. Although Table 5 indicates that dose

- based RQ s exceed acute risk LOCs across the uses assessed, subacute dietary toxicity data indicate that the

LC 50 exceeded the highest dietary co ncentration tested, i.e ., LC 50 >5,000 mg/kg diet. Residues on terrestrial forage items are subject to the same processes that occur in soil and lime sulfur is expected to rapidly dissociate to constituents that are generally regarded as safe; therefore, th e likelihood of exposure by birds to elevated levels of the parent compound is considered low. EFED cannot estimate the extent to which RQ values reported in Table 5 would be reduced; however, based on available data, current uses of lime sulfur do not ap pear to represent an actual risk to birds, terrestrial

- phase amphibians or reptiles. Similar to aquatic habitats, the likelihood of chronic exposure to lime sulfur is considered low given the rapid dissociation of the compound; therefore,

the likelihood o f adverse chronic effects from the compound is considered low.

Table 5

. Dose

- based Acute RQs for Birds Exposed to Calcium Polysulfides as Calculated by T

- REX Based on Maximum Application Rates

Crop Use (Application Rate) Body Weight

(g) Avian Risk Quotients a

Short

Grass Tall Grass Broadleaf Plants/Small

Insects Fruits/Pods/Large

Insects

Blueberries (66.58 lb a.i./A) 20 45.95 b 21.06 b 25.85 b 2.87 b

100 29.07 b 13.32 b 16.35 b 1.82 b

1,000 8.27 b 3.79 b 4.65 b 0.52 b

Grapes 20 42.43 b 19.45 b 23.87 b 2.65 b20 Crop Use (Application Rate) Body Weight

(g) Avian Risk Quotients a

Short

Grass Tall Grass Broadleaf Plants/Small

Insects Fruits/Pods/Large

Insects

(61.48 lb a.i./A) 100 26.84 b 12.30 b 15.10 b 1.86 b

1,000 7.64 3.50 b 4.30 b 0.48 c

Almond (49.18 lb a.i./A) 20 33.94 b 15.56 b 19.09 b 2.12 b

100 21.47 b 9.84 b 12.08 b 1.34 b

1,000 6.11 b 2.80 b 3.44 b 0.38 c

Apples (33.81 lb a.i./A) 20 23.34 b 10.70 b 13.13 b 1.46 b

100 14.76 b 6.77 b 8.30 b 0.92 b

1,000 4.20 b 1.93 b 2.36 b 0.26 c

Alfalfa (3.07 lb a.i./A) 20 2.12 b 0.97 b 1.19 b 0.13 c

100 1.34 b 0.61 b 0.75 b 0.08

1,000 0.38 c 0.17 c 0.21 c 0.02

a Ac ute dose

- based RQ = EEC/LD 50 , where EEC values are upper bound residues expressed as equivalent dose (mg a.i./kg body weight) generated from T

- REX and the toxicity value is the acute dose

- based LD 50 =560 mg a.i./kg diet in bobwhite quail.

b RQs are above the LOC for acute risk to both non

- listed (LOC 0.5) and listed species (LOC 0.1).

c RQs are above the LOC for acute risk to listed species (LOC 0.1).

Similar to the situation for birds and based on the dose

- based RQ values reported in Table 6 , acute risk LOCs are exceeded for mammals. However, the likelihood of mammals willingly consuming

a caustic solution of lime sulfur seems remote. While subacute dietary toxicity data are not available for mammals, the RQ values reported in Table 6 are not considered an accurate representation of the potential risk. Again though, EFED cannot estimate the extent to which RQ values would be reduced; however, based on available data, current uses of lime sulfur do not appear to represent an actual risk to mammals. As noted previously, likelihood of chronic exposure to lime sulfur is considered low given the rapid dissociation of the compound; therefore, the

likeliho od of adverse chronic effects from the compound is considered low.

Table 6

. Dose

- Based Acute RQs for Mammals Exposed to Calcium Polysulfides Calculated by T

- REX a Based on Maximum Application Rates

Crop Use (Application Rate) Body Weight

(g) Mammalian Acute Risk Quotients b

Short

Grass Tall Grass Broadleaf

Plants/Small

Insects Fruits/Pods/Large

Insects Seeds

Blueberries (66.58 lb a.i./A) 15 79.73 c 36.54 c 44.85 c 4.98 c 1.10 c

35 68.46 c 31.38 c 38.51 c 4.28 c 0.97 c21 Crop Use (Application Rate) Body Weight

(g) Mammalian Acute Risk Quotients b

Short

Grass Tall Grass Broadleaf

Plants/Small

Insects Fruits/Pods/Large

Insects Seeds

1,000 35.97 c 16.49 c 20.23 c 2.25 c 0.45 d

Grapes (61.48 lb a.i./A) 15 73.62 c 33.74 c 41.41 c 4.60 c 1.02 c

35 63.22 c 28.97 c 35.56 c 3.95 c 0.90 c

1,000 33.22 c 15.22 c 18.68 c 2.08 c 0.42 d

Almond (49.18 lb a.i./A) 15 58.89 c 26.99 c 33.13 c 3.68 c 0.81 c

35 50.57 c 23.18 c 28.44 c 3.16 c 0.72 c

1,000 26.57 c 12.18 c 14.95 c 1.66 c 0.33 d

Apples (33.81 lb a.i./A) 15 40.49 c 18.56 c 22.78 c 2.53 c 0.56 c

35 c 34.77 c 15.94 c 19.56 c 2.17 c 0.49 d

1,000 18.27 c 8.37 c 10.28 c 1.14 c 0.23 d

Alfalfa (3.07 lb a.i./A) 15 3.68 c 1.68 c 2.07 c 0.23 d 0.05

35 3.16 c 1.45 c 1.78 c 0.20 d 0.04

1,000 1.66 c 0.76 c 0.93 c 0.10 d 0.02

a EECs values are upper

- bound residues expressed as equivalent dose (mg a.i./kg body weight) generated from T

- REX.

b RQs calculated using the acute oral LD 50 value = 86.63 mg a.i./kg body weight in male rats.

c RQs are above t he LOC for acute risk to both non

- listed (LOC 0.5) and listed species (LOC 0.1).

d RQs are above the LOC for acute risk to listed speci es (LOC 0.1)

While no terrestrial plant toxicity studies were submitted, risk to listed and non

- listed terrestrial plants a re considered possible based on ecological incident reports involving plants

. Also li me sulfur is used to thin fruit and therefore can affect plants with abscission zones

.22 7. Endocrine Disruptor Screening Program

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, reproductive, and general or systemic toxicity. These studies include endpoints

, which may be susceptible to endocrine influence, including effe cts on endocrine target organ histopathology, organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and chronic

studies that assess growth, developmental and reproductive effects in different taxonomic groups. As part of registration review for lime sulfur, EPA reviewed these data and selected the most sensitive endpoints for relevant risk assessment scenarios from the exi sting hazard database. However, as required by FFDCA section 408(p), lime sulfur is subject to the endocrine screening part of the Endocrine Disruptor Screening Program (EDSP).

EPA has developed the EDSP to determine whether certain substances (includin g pesticide active and other ingredients) may have an effect in humans or wildlife similar to an effect produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator may designate.” The EDSP employs a two

- tiered approac h to making the statutorily required determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal systems. Chemicals that go through Tier 1 screening and are found to have the potential to interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tie r 2 testing is designed to identify any

adverse endocrine

- related effects caused by the substance, and establish a dose

- response relationship between the dose and the E, A, or T effect.

Under FFDCA section 408(p), the EPA must screen all pesticide chemic als. Between October 2009 and February 2010, EPA issued test orders/data call

- ins for the first group of 67 chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list of chemicals identified for EDSP screening was pu blished on June 14, 2013 8 and includes some pesticides scheduled for registration review and chemicals found in water

. Neither of these lists should be construed as a list of known or likely endocrine disruptors. Lime sulfur is not on List 1. For further

i nformation on the status of the EDSP, the policies and procedures, the lists of chemicals, future lists, the test guidelines and the Tier 1 screening battery, please visit our website. 9

8. Endangered Species Assessments

In November 2013, the EPA, along with the U.S. Fish & Wildlife Service (USFWS), the National Marine Fisheries Service (NMFS) (collectively, the Services) , and the U.S. Department of Agriculture (USDA) released a summary of their joint Interim Approaches for assessing risks to

8 See http://www.regulations.gov/#!documentDetail;D=EPA

- HQ

- OPPT

- 2009

- 0477

- 0074 fo r the final second list of

chemicals.

9 http://www.epa.gov/endo/23 listed species from pesticides. The Interim Approaches were developed jointly by the agencies in response to the National Academy o f Sciences’ (NAS) recommendations and reflect a common approach to risk assessment shared by the agencies as a way of addressing scientific differences

between the EPA and the Services. The NA S report outlines recommendations on specific scientific and technical issues related to the development of pesticide risk assessments that EPA and the Services must conduct in connection with their obligations under the Endangered Species Act (ESA) and FI FRA.

The joint Interim Approaches were released prior to a stakeholder workshop held on November 15, 2013. In addition, the EPA presented the joint Interim Approaches at the December 2013 Pesticide Program Dialogue Committee (PPDC) and State

- FIFRA Issue s Research and Evaluation Group ( SFIREG) meetings, and held a stakeholder workshop in April 2014, allowing additional opportunities for stakeholders to comment on the Interim Approaches. As part of a phased, iterative process for developing the Interim Ap proaches, the agencies will also consider public comments on the Interim Approaches in connection with the development of upcoming Registration Review decisions. The details of the joint Interim Approaches are contained in

the white paper “ Interim Approaches for National

- Level Pesticide Endangered Species Act Assessments Based on the Recommendations of the National Academy of Sciences April 2013 Report ,” dated November 1, 2013.

Given that the agen cies are continuing to develop and work toward implementation of the Interim Approaches to assess the potential risks of pesticides to listed species and their designated critical habitat, this preliminary risk assessment for lime sulfur does not contain a complete ESA analysis that includes effects determinations for specific listed species or designated critical habitat. Although EPA has not yet completed effects determinations for specific species or habitats, for this preliminary assessment EPA conducte d a screening

- level assessment for all taxa of non

- target wildlife and plants that assumes for the sake of the assessment that listed species and designated critical habitats may be present in the vicinity of the application of lime sulfur . This screening level assessment will allow EPA to focus its future evaluations on the types of species where the potential for effects exists once the scientific methods being developed by the agencies have been fully vetted.

This assessment for lime sulfur indicates p otential risks of direct effects to listed freshwater fish and invertebrates, bi r ds , and mammals on an acute exposure basis . The potential for risk to listed

and non

- listed terrestrial plants exists as well due to observed phytotoxicity. Listed species o f plant

- dependent taxa may also be affected through indirect effects because of the potential for

direct effects on listed and non

- listed species upon which such species may rely. Potential direct effects on listed terrestrial plants from the use of lime sulfur may be associated with modification of Primary Constituent Elements (PCEs) of designated critical habitats, where such designations have been made. Once the agencies have fully developed and implemented the scientific methods necessary to complete risk assessments for endangered and threatened (listed) species and their designated critical habitats, these methods will be applied to subsequent analyses for lime sulfur as part of completing this registration review

.24 9. Risk Conclusions

Although the problem formulation of this assessment hypothesized that b ased on the most sensitive toxicity values, direct exposure to calcium polysulfides from their use as a fungicide/acracide may

result in acute and chronic adverse effects to non

- target aquatic and terrestrial organisms, the

likelihood of direct acute exposure to the lime sulfur is considered low and the likelihood of chronic exposure is considered even more remote

. T he 2005 RED and 2015 new use assessments concluded that based on the relatively rap id dissociation of lime sulfur to constituents that are routinely found in the environment and generally regarded as safe, the likelih ood of adverse effects

on animals is low. The assessments also concluded that there is a low likelihood that elevated

res idues of potentially toxic constituents such as hydrogen sulfide will result in the environment

from agricultural us ag e of lime sulfur

, because the amount of sulfur add ed to the sulfur cycle from

such us es does not substantially contribute to the pool of s ulfur already present in reducing

environments. While caustic intermediates ( e.g ., CaOH) can form as lime sulfur dissociates, elevated levels of these compounds are expected to be short

- lived due to the natural buffering capacity of the soil/water. This current assessment has come to a similar conclusion

.

This assessment evaluated the potential risks to terrestrial and aquatic animals and has concluded that the likelihood of acute and chronic exposure is low; therefore, likelihood of adverse effects on

these taxa is considered low. Although t his assessment indicate d potential risks of direct effects

to freshwater fish on an acute exposure basis

, a pplication of calcium poly sulfides to targeted foliage/soils and its movement to water bodies by drift is e xpected to result in low concentrations of calcium polysulfides in these systems . Such quantities are not believed likely to significantly alter natural background levels of these elements in the environment nor are they expected to substantially alter th e pH of most receiving waters because of large dilution volume s and natural buffering capacity that is typically present. In a worst case scenario, the application of lime sulfur at the highest application rate would result in a decrease by 0.33 pH units. Such additions might potentially cause small alterations in the pH of a water body that has low buffering capacity;

howev er, minor fluctuations in pH are not expected to have direct impact on the aquatic life

contained therein. The use of oil formulations of lime sulfur is believed to further reduce the importance of drift as a transport pathway to water bodies. Similarly, for estuarine/marine systems, the likelihood of exposure is considered low, especially given the in herent buffering capacity of such systems; therefore, the likelihood of adverse effects on estuarine/marine organisms from the

use of lime sulfur is conside red low. Refer to Appendix A for additional information regarding alterations of pH in an aquatic system.

This assessment indicates potential risks of direct effects to listed birds and mammals on an acute

oral exposure basis. However, the likelihood that sufficient quantities of the material would remain on dietary forage items to represent a risk to birds or mammals on a subacute dietary exposure basis is considered low. Although EFED has no data to support the contention that

neither birds or mamma ls would willingly consume caustic solutions of lime sulfur, the likelihood of this occurring is considered low. A lthough lime sulfur can move from application sites to adjacent land s via drift from treated areas, the material is expected to rapidly dissociate into mainly

sulfur and calcium ions, which are not believed likely to substantially alter natural background

levels of these elements in the environment.25 Although calcium polysulfides can be applied multiples times per year, due to the short half

- life, multiple applications are not expected to result in accumulation of the parent compound on terrestrial forage items. G iven the rapid dissipation, c hronic exposure to calcium polysulfides is not expected. T he use and application of calcium poly sulfides are not expected to significantly

increase the total calcium or sulfur content of soils and/or forage surfaces above background levels

. In a worst case scenario, the application of lime sulfur on the terrestrial environment at the highest applica tion rate will lower (acidify) acidic or neutral soils by less than 0.5 pH units. Refer to Appendix A for additional information re garding pH alterations in terrestrial environments

.

Potential risks to terrestrial invertebrates is an uncertainty. On an acute contact exposure basis, lime sulfur is practically non

- toxic to honey bees. The compound is not expected to persist in the environment and the extent to which it could be brought back to the colony to expose in

- hive bees may be limited given the humid conditions which exist in honey bee colonies, since such conditions would likely promote the dissociation of the compound. There is anecdotal information to suggest that if bees are foraging at the time of application, they may be affected. Other beneficial insects though, that may be in their larval form, such as those reported in the effects characterization may be at risk if exposed at the maximum application rate.

The use of lime sulfur may represent a potential for risk to listed and non

- listed terrestrial plants given that the compound can affect plant abscission and there are incident data to support concerns regarding phytotoxicity. Because of potential risks to t errestrial plants, secondary effects to plant

dependent taxa may also occur. Th is uncertainty is amplified by the lack of terrestrial plant toxicity

data and could be reduced if such data were provided

.

10. Literature Cited

ATSDR. 2004. Agency of Toxic Su bstances and Disease Registry U.S. Department of Health and Human Services Public Health Service. Toxicological Profile for Hydrogen Sulfide. September 2004.

Atkinson, JD, Brian RM, Chamberlain EE, Cottier W, Dingley JM, Jacks H, Reid WD, Taylor GG. 1956. Plant Protection in New Zealand. Wellington, New Zealand: Government Printer, 699 pp.

Baird, C. Environmental Chemistry 2 nd edition, W.H. Freeman and Co mpany, New York \ , NY.

2003.

Balls PW and Liss PS. 1983. Exchange of H 2 S between water and air. Atmos. Environ. 17:735

- 742.

Bartlett, B.R. 1964. The toxicity of some pesticide residues to adult Amblyseius hibisci, with a compilation of the

effects of pesticides upon Phytoseiid mites. J. Econ. Entomol. 57(4):559

- 562.

Bartlett, B.R. 1966. Toxicity and acceptance of some pesticides fed to parasitic hymentoptera and predatory Conccinellids. J. Econ. Entomol. 59(5):1142

- 1149.

Elliot S and Rowland FS. 1990. The effect of metal complexation on the hydrogen sulfide transport across the sea

- air interface. J. Atmos. Chem. 10:315

- 327.26 Bodek, I.T, Lyman, W.J., Reehl, W.F., Rosenblatt, D.H. 1988. Environmental Inorganic Chemistry. Properties, Processes and Estimation Methods. Pergamon Press. New York, NY. PP 8.2

- 1 to 8.2

- 10.

Holb, IJ, DeJong PF, and Heijne B. 2003. Efficacy and phytotoxicity of lime sulphur in organic apple production. Ann. Appl. Biol. 142 (2): 225

- 233.

Elliot S and Rowla nd FS. 1990. The effect of metal complexation on the hydrogen sulfide transport across the sea

- air

interface. J

. Atmos. Chem. 10:315

- 327.

James, D.G. and Rayner, M. 1995. Toxicity of viticultural pesticides to the predatory mites Amblyseius victoriensi s and Typhlodromus doreenae. Plant Protection Quarterly 10(3):99

- 102.

Jørgensen BB. 1982. Ecology of the bacteria of the sulphur cycle with special reference to anoxic

- oxic interface

environments. Philos. Trans. R. Soc. Lond. B. Biol. Sci. 298:543

- 561.

Llewelyn, FWM. 1965. The ‘hardening effect of lime

- sulphur sprays on maiden apple trees. Ann. Appl. Biol.

55:495

- 501.

McCann, J.A. 1976. Miller Lime Sulfur Solution: Acute Toxicity to Rainbow Trout: Test No. 1041. Biological Report of Analysis. U.S. Environmental Protection Agency, Pesticides Regulation Division, Animal Biology Section (Fish). unpublished report.

Shipton, PJ. 1969. Observations on the phytotoxicity and other effects of fungicides used on black currents. Plant

Pathol. 18: 133

- 137.

Smith KA, Bremner JM, Tabatalag MA. 1973. Sorption of gaseous atmospheric pollutants by soils. Soil Sci.

116:313

- 319.

Tate, KG, Manktelow DW, Walker JT, and Stiefel H. 2000. Disease management in Hawke’s Bay Apple Orchards converting to organic production. New Zealand Plant Protection 53: 1

- 6.

Tomlin C. 1994. Pesticide Manual 10th edition. British Crop Protection Council. The Royal Society of Chemistry, Cambridge U.K.

USEPA, 1998 . Guidance for Ecological Risk Assess ment. Risk Assessment Forum. EPA/630/R

- 95/002F, April

1998.

US EPA, 2002. Hydroxides Tolerance Reassessment Eligibility Decision (TRED). Federal Register: July 24, 2002.

USEPA, 2005. Environmental Fate and Ecological Risk Assessment for the Reregistration Eligibility Decision Document (RED) of Calcium Polysulfides, a Fungicide/acaricide. DP Barcode: D313165. Date: October 4,

2005

.

USEPA, 2013 Environmental Fate and Eff ects Preliminary Risk Assessment for the Registration Review of Sulfur. From Melendez, J. and Sappington, K. to Gayoso, J.; Britton, C.; and Costello, K.

USEPA, 2015

. Environmental Fate and Ecological Risk Assessment for Proposed Use of Calcium Polysulfide (Lime Sulfur Solution) on Apple Blossom Thinning. DP Barcod e: D422723 . Date: March 17, 2015.27 11. A ppendix A: The Sulfur Cycle

Sulfur is a natural component of the environment. In its elemental and oxidized forms, sulfur is estimated to represent 1.9% of the total weight of the earth. In soils and sediments, sulfur cycling

involves the transformation of sulfur between its +6 and

- 2 oxidation states. These reactions are largely mediated by microorganisms. The reduction of sulfate to sulfide by microorganisms such as the sulfate reducing D esulfovibrio bacteria, occurs in virtually any anaerobic habitat containing organic matter an d sulfates . Hydrogen sulfide is oxidized by chemosynthetic bacteria known as colorless sulfur bacteria, which oxidize sulfide in the presence of oxygen, and by photosynthetic green and purple bacteria. The oxidation of hydrogen sulfide to sulfate is also accomplished by

T

hiobaccilli bacteria (aerobic sulfide oxidizers). The critical nature of the microbial process is underscored by the fact that there is no known chemical reaction for the reduction of sulfur from

its +6 oxidation state to its S

- 2 state a t ambient temperature and pressure, and that 50

- 60% of global sulfur oxidation is estimated to occur through microbial processes.

Sulfur may be reduced to form hydrogen sulfide. In aqueous solution, hydrogen sulfide is a weak acid, exhibiting two acid dissociation constants. The first dissociation yields bisulfide anion (HS

– ), and the second yields sulfide anion (S 2

– ); the pK
a values for each of these dissocia tions are 7.04 and 11.96, respectively. At a pH of 7, the ratio of the concentration of aqueous hydrogen sulfide to bisulfate ion is approximately 1

- to

- 1. As the pH increases above 7, the ratio of concentration of bisulfide ion to aqueous hydrogen sulfide increases. Only above pH 12 will the concentration of sulfide ion become significant (>50%)

. Hydrogen sulfide is usually not a long

- lived chemical species in the environment. In soils and water, hydrogen sulfide reacts with iron and other

transition met als to form insoluble sulfides; however, where iron levels are low H 2 S may accumulate to toxic levels (Bodek et al . 1988). Several species of soil, aquatic, and marine microorganisms oxidize hydrogen sulfide back to elemental sulfur or various sulfates, a nd its half

time in these environments usually ranges from 1 hour to several hours (Jørgensen 1982). Hydrogen sulfide evaporates readily from surface water, and the rate of evaporation depends on factors such as temperature, humidity, pH, depth of the wat er body, and the concentration of certain metal ions. Hydrogen sulfide will cross the air

- water interface with kinetics similar to other unreactive gases, such as oxygen (O 2 ), nitrogen (N 2 ), and carbon dioxide (CO 2 ), at pHs ≤ 6 (Balls and Liss 1983). Bis ulfide and sulfide ions will form complexes with trace metal ions (i.e., Zn 2+

, Co 2+ , and Ni 2+ ) found in seawater (Elliot and Rowland 1990). Ambient atmospheric levels of hydrogen sulfide from natural sources are reported to range from about 0.11 to 0.33 p pb (0.15 to 0.46 μg/m 3 ) (ATSDR 2004).

Clay or organic matter may adsorb hydrogen sulfide, effectively acting as an environmental sink.

Smith et al. (1973) determined the sorption characteristics of hydrogen sulfide to six air

- dried and

moist soils in a laboratory study. The capacities of soil samples to sorb hydrogen sulfide ranged from 15.4 to 65.2 mg/g soil for the air

- dried soils, and from11.0 to 62.5 mg/g soil for the moist soils (50% of field capacity). Capacities and rates of sorption were not si gnificantly affected by sterilization of the soil sample, indicating that soil microorganisms are not likely to be involved in the sorption process. The authors noted that these values, however, would not provide reliable estimates of the amounts of hydro gen sulfide that could be sorbed by soils under natural conditions, where the environmental fate of the sorbed hydrogen sulfide would have to be considered. UnderPage 28 of 30 natural conditions, it is likely that some of the hydrogen sulfide would be oxidized to sulf ate, which may be removed by leaching or taken up by plants. This, in turn, may make gas sorption sites available for additional sorption (Smith et al . 1973).

S cenario in soil 10

The worst case calculation for pH change in soil will be for soils that are acidic, neutral or

contain no CaCO 3 ( i.e ., minimal buffering capacity). For neutral and acidic soils, the addition of

217 lbs of CaS 5 is calculated to decrease pH (increase acidity) by 0.5 pH units in coarse textured soils (sands, loamy sands), and 0. 2 pH units in fine textured soils (loams, clay loam, clay).

The maximum application rate of CaS 5 /A is ~217 lbs a.i./A. Because there is 80% sulfur in the

CaS 5 (5 x 32=160 g/mol) the sulfur application rate is 173.6 lbs a.i./A.

Coarse Textured Soils (6 six inches deep soil) In order to change the pH 0.5 unit; Use ratio where d1=pH unit change d1pH unit/352 lbs S/A=X/173.6 lbs S/A; Solve X=173.6/352

Fine Textured Soils (6 six inches deep soil) In order to change the pH 0.2 pH unit; Use ratio d1pH unit /1054 lbs S/A=X/173.6 lbs S/A; Solve

X=173.6/1054

Assuming that there is no contribution from CaCO 3 in soil (low buffering capacity), the

concentrations of CaS 5 needed to change the pH are a lot higher than the maximum annual application rate of sulfur.

Scenario in aqueous solution due to Spray Drift Alone 9

The pH change due to spray drift deposition of sulfuric acid in the standard pond was assessed.

The resulting concentrations were multiplied by 2 to account for the two acidic protons in

H 2 SO 4 , a nd converted to a molarity basis (see page 22 for equations) . Waters with low alkalinity (20 mg/L as CaCO 3 ) w ere assumed to test the effect of added acidity on poorly

buffered habitats.

This process in the environment can be very complex, therefore for simplicity, it was assumed that the only species providing buffering capacity i s bicarbonate (HCO 3

- ) , in a close system and

the initial pH is 7. The amount of hydrogen ion (x) entering the pond was used to change the

amount of HCO 3 - (

- x) and H 2 CO 3 (+x) i n the following equilibrium; given the pK
a for H 2 CO 3 as 6.37*:

10 http://articles.extension.org/pages/13046/raising

- soil

- ph

- and

- soil

- acidification

9 General Chemistry by Linus Pauling: Published April 1st 1988 by Dover Publications (first published June 8th 1970)Page 29 of 30 

## [ ] 

# [ ] 

# [ ] [ ] 

# [ ]
[ ] 7 E 55

. 4 CO H HCO H HCO H CO H

3 2 3

3 3 2 − = = + ⇔ − +

− +

a K Equation 1

At pH 7 ( Equation 2 ) , the ratio of bicarbonate ion [HCO 3 - ] to carbonic acid [H 2 CO 3 ] molarity is given by the ratio of the equilibrium constant K
a to the h ydrogen ion [H + ] concentration:



# [ ] 

# [ ]
[ ] ( ) ( ) 55

. 4 7

- E 1 7

- 4.55E

CO H HCO

H 3 2 3

= = = −

+ a K Equation 2

For a given alkalinity at pH 7, the amount of bicarbonate is 4.55 times the carbonic acid

concentration. Calculations u sing the maximum amount of lime sulfur that can reach the pond via spray drift (refer to page 17 for a detail discussion) ~120 μg/L, the molecular weight of CaS 5 (200 g/mol) and the initial concentrations of bicarbonate (2.00E

- 4 M) and carbonic acid (4.40E

- 4
M) were used to determine the final pH change when applying lime sulfur.

Thus, at 20 mg/L alkalinity (lower end of s urface water alkalinity range) and considering that for each sulfur entering the environment two protons are release to the environment.

The amount of H + added by spray drift (x) is used to shift the equilibrium (used to change the amount of bicarbonate ion (

- x) and carbonic acid (+x) in the equation ); and compute the new pH by rearranging E quation 2 : The amount of hydrogen ion (x) entering

[H + ] = K a x {[H 2 CO 3 ] / [HCO 3 - ]} Equation 3

Thus, using Equation 3 11 and the values mentione d above, the pH in pond water can change from

7.00 to 6.99.

Table 1 Pond

- water pH changes due to application of Lime sulfur *

Application

Method Low Water Alkalinity (20 mg/L) ** Initial pH Final pH

Aerial 7.00 6. 99

*: The CRC Handbook of Chemistry and Physics. 69 th Ed; p. D

- 163

**: Levels of 20

- 200 mg/L as CaCO 3 are typical of fresh water.

Assuming that there is low buffering capacity in pond water, the concentrations of CaS 2 needed to change the pH in water are a lot higher than the spray drift obtained using maximum annual application rate of lime sulfur.

11 General Chemistry by Linus Pauling: Published April 1st 1988 by Dover Publications (first published June 8th 1970)Page 30 of 30 A ppendix B: Output from OPP Agg regate Incident Database for Lime Sulfur