Docket Number EPA-HQ-OPP-2007-1140 

www.regulations.gov 

Silica Gel and Silicon Dioxide 

Proposed Interim Registration Review Decision 

Case Number 4081 

June 2015 

Approved by: ~nCLLCl e Y~r-: --i t_A_/ 0-) 

Richard P. Keigwin, Jr. 

Director 

Pesticide Re-evaluation Division 

Date: {J) / .J '-+ / . 0 I S 
Table of Contents 

Contents 

I. Introduction ............................................................................................................................. 3 

II. Use and Usage ......................................................................................................................... 4 

Ill . Scientific Assessments ............................................................ .................... ...... ...................... 5 

A. Human Health Assessment .................................................................................................... 5 

Hazard Characterization and Dietary Risk .................. ................................................... ........ 5 

Residential and Occupational Exposure ................................................................................. 5 

Aggregate Exposure and Risks ............................................................................................... 5 

Food Tolerances ...................................................................................................................... 5 

Hu1nan Incidents ..................................................................................................................... 5 

B. Environ1nental Assessment ................................................................................................... 6 

Environmental Fate and Exposure .......................................................................................... 6 

Ecological Risk Conclusions ...................................................................... ... ......................... 7 

Endangered Species Assessment ............................................................................................ 7 

Ecological Incidents ......................................................................... ............... ... ..................... 9 

C. Endocrine Disruptor Screening Program .............................................................................. I 0 

IV. Proposed Interim Registration Review Decision ............................................................... I 0 

A. Pollinator Studies and Assessment .................................................................... ....... ........... 11 

V. Next Steps and Timeline .......................... .......................................................................... 12 

2 
I. Introduction 

This document is the Environmental Protection EPA's (EPA or the EPA) Proposed 

Interim Registration Review Decision for silica gel and silicon dioxide (silicates, silica silicates 

or diatomaceous earth (DE)) and is being issued pursuant to 40 CFR sections 155.56 and 155.58. 

A registration review decision is the EPA's determination whether a pesticide meets, or does not 

meet, the standard for registration in the Federal Insecticide, Fungicide, and Rodenticide Act 

(FIFRA). The EPA may issue, when it determines it to be appropriate, a proposed interim 

registration review decision before completing a registration review. Among other things, the 

proposed interim registration review decision may require new risk mitigation measures, impose 

interim risk mitigation measures, identify data or information required to complete the review, 

and include schedules for submitting the required data, conducting the new risk assessment and 

completing the registration review. Further information on silica gel and silicon dioxide, can be 

found in EPA 's public docket (EPA-HQ-OPP-2007-1140) at www.regulations.gov. 

FI FRA, as amended by the Food Quality Protection Act (FQPA) of 1996, mandated the 

continuous review of existing pesticides. All pesticides distributed or sold in the United States 

generally must be registered by the EPA based on scientific data showing that they will not cause 

unreasonable risks to human health or to the environment when used as directed on product 

labeling. The registration review program is intended to make sure that, as the ability to assess 

and reduce risk evolves and as policies and practices change, all registered pesticides continue to 

meet the statutory standard of no unreasonable adverse effects. Changes in science, public 

policy, and pesticide use practices will occur over time. Through the registration review 

program, the EPA periodically reevaluates pesticides to make sure that as these changes occur, 

products in the marketplace can continue to be used safely. Information on this program is 

provided as www.epa.gov/oppsrrd I /registration review/. 

The Reregistration Eligibi lity Decision document (RED) for silica gel and silicon dioxide 

was completed in September 1991. In 2008, EPA initiated the registration review of silica gel 

and silicon dioxide with the opening of the silica gel and silicon dioxide registration review 

public docket (docket number EPA-HQ-OPP-2007-1140, accessible at www.regulations.gov.) 

Silica gel and silicon dioxide are formulated as dust or wettable powders (and sometimes 

combined with pyrethrins and piperonyl butoxide (PBO)) and have both indoor and outdoor uses 

in both commercial (e.g. , rights of ways, nursery greenhouses and industrial sites) and residential 

settings (e.g. , landscape maintenance, lawn and structural pest control) . 

Pursuant to 40CFR§155.50, the EPA initiated registration review for case no. 4081 

which includes silica gel (PC code no. 072602) and si licon dioxide (PC code no. 072604). The 

following timeline highlights significant events that have occurred during the registration review 

of silica gel and silicon dioxide: 

• March 26, 2008 - The EPA published the Silica and Silicates Summary Document, dated 

March 14, 2008 in docket number EPA-HQ-OPP-2007-1140 for a 60-day public 

comment period. The Summary Document included the EPA's Preliminary Work Plan 

for Silica and Silicates, the Problem Formulation.for Ecological Risk Assessment.for 

3 
Silicon Dioxide and Silica Gel, dated November 16, 2007 and the HED Registration 

Review Scoping Document, dated November 16, 2007. 

• August 05, 2008 - The EPA published the Silica and Silicates Final Work Plan. The 

EPA indicated that it would conduct a comprehensive ecological risk assessment that 

included an endangered species risk assessment, and that EPA would not conduct a 

human health risk assessment for the silica gel and silicon dioxide registration review. 

• December I 0, 2009 - Generic Data Call-In (GDCl-072602-847) for silica gel and silicon 

dioxide was issued. Data required by the EPA included: 

o GLN 830.7050: UV/Visible absorption 

o GLN 850.2100: Avian acute oral toxicity test 

• March 07, 2013 - The EPA published the Environmental Fate and Ecological Risk 

Assessment for the Registration Review of Silica, dated January 16, 2013 for a 60-day 

public comment period, during which time, no comments were received . 

• June 24, 2015 - The EPA is now publishing the Silica and Silicates Proposed Interim 

Registration Review Decision, in docket number EPA-HQ-OPP-2007-1140, for a 60-day 

public comment period. 

Additional information on silica gel and silicon dioxide can be found in the public docket, 

EPA-HQ-OPP-2007-1140, which can be accessed at www.regulations.gov. 

II. Use and Usage 

Silica gel and silicon dioxide are both derived from DE deposits which are commonly 

found in most soils. Silicon dioxide is DE, a naturally-occurring material composed of the shells 

of minute, single-celled algae . Unlike silicon dioxide, silica gel has no registered outdoor uses. 

Silica gel is characterized as the amorphous form of silicon dioxide, which is made by the 

gelation of sodium silicate and sulfuric acid. Because silica gel has no outdoor uses, the EPA 

considered environmental exposure solely from silicon dioxide when conducting its 

environmental fate and effects assessment. What little use data on silica gel and silicon dioxide 

is available indicates that less than 50,000 pounds is used annually. 

4 
III. Scientific Assessments 

A. Human Health Assessment 

A summary of the EPA's human health analysis is presented below. For detailed 

information on EPA's human health assessment for silica gel and silicon dioxide, see the Silica 

and Silicates Registration Review Summary Document, dated March 14, 2008, available in the 

public docket found at EPA-HQ-OPP-2007-1140-0005, which can be accessed at 

http://www.regulations.gov/. 

Hazard Characterization and Dietary Risk 

No toxicological endpoints were identified in the silica gel and silicon dioxide hazard 

database due to its low toxicity. The EPA believes that exposure to silica gel and si li con dioxide 

from direct or indirect app lication to food commodities, or from residues in food handling and 

food preparation areas, would not result in risks of concern. The Food and Drug Administration 

(FDA) has classified si licon dioxide and silica gel as Generally Recognized as Safe (GRAS) food 

additives (21 CFR 182.90 and 182.1711 ). In addition, silicon dioxide has been exempted from 

the requirement of a tolerance when applied to growing crops and raw agricultural commoditi es 

after harvest and to animals (40 CFR 180.1017 (a) and (b); and in food and feed processing and 

storage areas (40 CFR 185.1700 and 186.1700). Based upon these considerations, EPA 

determined that a quantitative human health risk assessment was not needed for silica gel and 

silicon dioxide, and therefore a dietary (food + drinking water) assessment was not conducted. 

Residential and Occupational Exposure 

Silica gel and silicon dioxide are registered for homeowner uses (including crack and 

crevice treatment, pets, and etc.); therefore there is the potential for applicator and postapplication residential exposures to occur. However, based on the low toxicity of silica gel and 

silicon dioxide, the EPA has determined that residential exposures to these compounds would not 

be of concern, and, consequently, neither a residential handler nor a residential post-application 

assessment are needed . 

While silica gel and silicon dioxide labels require the use of a respirator to protect 

against irritating particles, the EPA has not identified any toxicological endpoints appropriate for 

a quantitative occupational assessment. Therefore, the EPA believes that neither occupational 

handler nor occupational post-application exposures would be of concern, and concluded that an 

occupational assessment is not needed. 

Aggregate Exposure and Risks 

Due to the EPA's determination not to conduct either a dietary (food and drinking water) 

or residenti al risk assessment for the silicates, an aggregate risk assessment was not needed. 

5 
Food Tolerances 

Silica gel and silicon dioxide have been exempted from the requirement of a tolerance 

when applied to growing crops and raw agricultural commodities after harvest (40 CFR 

180.100 I (c) and (d), to growing crops, raw agricultural commodities after harvest and animals 

(40 CFR 180.1017); and in food and feed processing and storage areas (40 CFR 185.1700 and 

186.1700). 

Human Incidents 

Based on a search conducted on June 2, 2015, the Agency's Incident Data System (IDS) 

has approximately 280 reported incidents associated with silica gel and silicon dioxide (between 

January I, 20 I 0 to June 2, 2015). Of the reports identified in IDS database, 11 cases involved 

either silica gel or silicon dioxide (I 0 of moderate severity, and I of major severity). The one 

major severity case involved an 18-year old female who started experiencing migraines and 

seizures about a week after her mother treated their home (floorboards and baseboards). 

On June 2, 2015, the Agency also consulted the Centers for Disease Control and 

Prevention/National Institute for Occupational Safety and Health (CDC/NIOSH) Sentinel Event 

Notification System for Occupational Risk (SENSOR) database, and identified 138 cases from 

1998 to 2011 involving silica gel and silicon dioxide. Of the reports identified in the SENSOR 

database, 9 cases involved a single active ingredient, either silica gel or silicon dioxide (all cases 

were of low severity). Also, all 9 cases were worker related, 5 of which were related to a single 

work event where silica dust was applied, and subsequently vacuumed in an office area while 

employees were present. 

B. Environmental Assessment 

A summary of the EPA's environmental assessment for silica gel and silicon dioxide is 

presented below. For detailed discussions of all aspects of the environmental risk assessment, see 

the Environmental Fate and Ecological Effects Risk Assessment for the Registration Review of 

Silica, (dated January 16, 2013), available in the public docket EPA-HQ-OPP-2007-1140 which 

can be accessed on http://www.regulations.gov/. 

Environmental Fate and Exposure 

While silica gel and silicon dioxide are registered for use on a variety of agricultural 

crops, turf, industrial sites and homeowner uses, it is rarely applied as a broadcast, but more as a 

spot treatment. Therefore, movement of silica gel and silicon dioxide away from the treatment 

site via wind or rain is expected to be limited. Further, the U.S. Geological Survey (1984) reports 

that both silica gel and silicon dioxide are components of U.S. soils at approximately 2- 31 %. 

While silica gel and silicon dioxide can potentially be transported to aquatic environments, 

exposure to aquatic organisms is not considered to be a concern since the mode of action of the 

of these compounds is negated when wet (i.e., upon becoming wet, silica gel and silicon dioxide 

will clump, and thereby lose the ability to cut and desiccate target organisms). 

6 
Ecological Risk Conclusions 

I. Terrestrial Species 

Based upon the low toxicity of silica gel and silicon dioxide, its ubiquitous presence in 

the environment, and its limited use as a pesticide, the EPA determined that a quantitative 

ecological assessment was not required for registration review. 

Based on available data, terrestrial vertebrates (including birds and mammals) are 

unlikely to be harmed from either dietary or dermal exposure to these compounds. Further, 

because of the ubiquitous nature of the silica gel and silicon dioxide, terrestrial invertebrates 

living on and in the soil are likely to have adapted to the these compounds. However, EPA does 

expect that terrestrial invertebrates that do not live in or on the soil, (e.g. , flying or leaf-dwelling 

insects), may be adversely affected by silica gel and silicon dioxide due to its insecticidal 

properties (i.e. to cut and dessicate). 

2. Aquatic Organisms 

As noted above, because the mode of action is negated when silica gel and silicon dioxide 

become wet, the EPA does not anticipate that these compounds will adversely affect aquatic 

organisms (fish or invertebrates). 

3. Plants 

Because terrestrial plants are likely to be routinely exposed to silica as wind-borne 

particles, and because both terrestrial and aquatic plants produce a form of silica (biogenic 

amorphous silica), adverse effects to plants (either terrestrial or aquatic) are not anticipated from 

exposure to silica gel or silicon dioxide. 

Endangered Species Assessment 

The ecological risk assessment supporting the EPA 's registration review decision for 

silica gel and silicon dioxide contains a completed Endangered Species Act (ESA) analysis, 

including effects determinations for endangered and threatened (listed) species and their 

designated critical habitat, and incorporates concurrence from the U.S. Fish and Wildlife Service 

(FWS) on EPA's "Not Likely to Adversely Affect (NLAA)" determination, based on informal 

consultation. 

While EPA did not conduct a quantitative analysis of silica gel and silicon dioxide for 

either listed or non-listed species as part of its ecological assessment, EPA made a "No Effect" 

determination for all listed species, with the exception of 57 listed terrestrial invertebrate species 

for which an NLAA finding was determined. The EPA reached this conclusion based upon the 

following rationale: 

I. Silica gel and silicon dioxide have a mechanical rather than a toxic mode of 

action; therefore, the potential for adverse effect is limited in time and space 

7 
to the treated area, not off-site, and to a short interval after applications, since 

weathering renders silica gel and silicon dioxide inefficacious. Although the 

time to effective weathering is not quantified, it is expected to be no longer 

than to the next rainfall. 

2. Silica gel and silicon dioxide are naturally occurring substances, wide-spread 

in many soils at low concentrations. Thus, listed species are expected to be 

exposed to these compounds and are presumably adapted to low exposure 

concentrations. 

3. It is uncertain whether listed terrestrial invertebrate species would visit treated 

areas, or remain on these areas during the time of application, due to the 

attendant human disturbance. 

4. Silica gel and silicon dioxide are used in organic agriculture and by 

homeowners seeking less-toxic alternatives to conventional pesticides. To the 

degree that silica gel and silicon dioxide are used in place of conventional 

insecticides, EPA believes that the silicates are a much safer alternative in 

terms of any potential impacts to listed terrestrial invertebrates. 

On February I 0, 2014, pursuant to section 7 of the ESA, EPA requested informal 

consultation with the FWS on silica gel and silicon dioxide, and concurrence with the NLAA 

determination for 57 listed terrestrial invertebrate species. 

On April 2, 2014, FWS issued a letter to EPA indicating its concurrence with the EPA's 

NLAA determinations for silica gel and silicon dioxide on 57 listed terrestrial invertebrates (see 

Appendix). In an email that preceded the April 2, 20 I 4 letter, the FWS noted that one species, 

the Ash Meadows naucorid (Ambrysus amargosus) should be included among the listed species 

identified, and that there is "No Effect" to this species from silica gel and silicon dioxide 

(personal communication, email from Patrice Ashfield to Anita Pease, March 31, 2014). 

Subsequent to the issuance of FWS's concurrence letter, the FWS Oregon Field Office 

highlighted potential concerns for specific silica gel and silicon dioxide use sites (i.e ., pastures, 

vineyards) for two listed species of butterfly, namely the Fender's Blue butterfly (lcaricia 

icarioidesfenderi) and the Taylor's Checkerspot butterfly (Euphydryas editha taylori). This 

concern resulted in further work between EPA and FWS to ensure no adverse effects to these 

two species of butterfly was likely from exposure to silica gel and silicon dioxide use in pastures 

and vineyards. EPA provided additional information to the FWS regarding existing state-level 

pollinator protection requirements for silica gel and silicon dioxide, which are triggered by a 

state decision to register these compounds for a new use (via a section 18 or 24c label), and 

similar guidance available through other extension services. EPA also provided FWS with 

additional data showing low toxicity of silica gel and silicon dioxide to bees (used as a surrogate 

for butterflies) at rates exceeding current application levels. Based on this additional information 

provided by EPA, the FWS reaffirmed their concurrence with EPA's NLAA determination for 

the Fender's Blue and Taylor's Checkerspot butterflies (see Appendix for letter from C.Aubrey 

of U.S. FWS to A.Pease of U.S. EPA dated March 9, 20 15). 

8 
EPA does not anticipate conducting any further analysis of silica gel and silicon dioxide 

for potential risks to listed species and/or designated critical habitat unless additional data or 

information are obtained that would otherwise inform this determination. 

Ecological Incidents 

On May 16, 2012, EPA searched its ecological incident databases, including the 

Ecological Incident Information System (EIIS), the Avian Incident Monitoring System (AIMS), 

and the Aggregate Incident Reports database. In the EllS, one ecological incident was identified 

that occurred in Texas in 1994 and involved six fish with possible exposure to silica gel. The 

incident was reported as an " intentional misuse" and considered "possibly" caused by silica gel, 

since there are no outdoor uses of silica gel. Furthermore, the product associated with the 

incident contained a pyrethroid and PBO. No ecological incidents were reported through the 

AIMS or the Aggregate Incident Reports database. 

C. 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 effects 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 its most recent registration decision for silica gel and 

silicon dioxide, EPA reviewed these data and selected the most sensitive endpoints for relevant 

risk assessment scenarios from the existing hazard database. However, as required by FFDCA 

section 408(p), silica gel and silicon dioxide are subject to the endocrine screening part of the 

Endocrine Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including 

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 approach to making the 

statutorily required determinations. Tier I 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 I 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. Tier 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 chemicals. Between 

October 2009 and February 20 I 0, EPA issued test orders/data call-ins for the first group of 67 

9 
chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list of 

chemicals identified for EDSP screening was published on June 14, 2013 1 and includes some 

pesticides scheduled for Registration Review and chemicals found in water. For further 

information on the status of the EDSP, the policies and procedures, the lists of chemicals, future 

lists, the test guidelines and the Tier I screening battery, please visit our website. 2 

In the interim, EPA is making no human health or environmental safety findings 

associated with the EDSP screening of the silica silicates (silica gel and si licon dioxide). Before 

completing this Registration Review, the Agency will make an EDSP FFDCA section 408(p) 

determination . 

IV. Proposed Interim Registration Review Decision 

EPA has completed qualitative human health and ecological risk assessments, including 

an endangered species assessment for silica gel and silica dioxide. The EPA has also updated its 

silica gel and silicon dioxide data base by receiving the following data required under the 

registration review GDCI (GDCl-072602-847). 

• GLN 830.7050: UV/Visible absorption 

• GLN 850.2100: A vi an acute oral toxicity 

The EPA has determined that no human health risks are expected from the use of 

pesticide products that contain silica gel and silicon dioxide. The EPA has also determined that 

potential ecological effects from the use of pesticide products that contain silica gel and silicon 

dioxide would only be expected for terrestrial invertebrates that do not live in or on the soil, (e.g. 

flying or leaf-dwelling insects). The EPA believes that potential effects to these species would be 

limited in time, since the effects of silica gel and silicon dioxide only last until a rainfall event 

occurs (when the rain would cause the compounds to clump and lose its mode of action). In 

addition, EPA believes the potential effects to terrestrial invertebrates would also not be 

geographically widespread since silica gel and silicon dioxide are typically applied as a spot 

treatment. 

In accordance with 40 CFR Sections 155 .56 and 155.58, the EPA is issuing this Proposed 

Interim Registration Review Decision. Pending the outcomes of EDSP analysis for silica gel and 

silicon dioxide, the EPA has made the following Proposed Interim Decision: 

• No changes are proposed to silica gel and silicon dioxide registrations or their labeling; 

• EPA has made a "No Effect" determination under the Endangered Species Act (ESA) for 

all listed species, excluding 57 listed terrestrial invertebrate species, for which a NLAA 

determination was made, and no modification of designated critical habitat for such 

species. In letters dated April 2, 2014, and March 8, 2015, the FWS indicated its 

concurrence with the EPA's conclusion that silica gel and silicon dioxide are NLAA the 

57 listed terrestrial invertebrate species. 

1 See http://www.regulations.gov/# !documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals. 

2 http://www.epa.gov/endo/ 

10 
V. Next Steps and Timeline 

A. Interim Registration Review Decision 

A Federal Register Notice will announce the availability of this Proposed Interim 

Registration Review Decision for silica gel and silicon dioxide and allow a 60-day comment 

period. lfthere are no significant comments or additional information submitted to the docket 

during the comment period that leads the EPA to change its proposed decision, EPA may issue 

an Interim Registration Review Decision for silica gel and silicon dioxide (case 4081 ). 

However, a final decision for silica gel and silicon dioxide may be issued without having 

previously issued an interim decision. A final decision on the silica gel and silicon dioxide 

registration review case will occur after an EDSP FFDCA section 408(p) determination has been 

completed. 

11 
Appendix 

FWS Correspondence for Informal Endangered Species Consultation on 

Silica Gel and Silocon Dioxide 

12 
United States Department of the Interior 

FISH AND WILDLIFE SERVICE 

Washington, D.C. 20240 

In Reply Refer To: 

FWS/ AES/DER/BCW05706 l 

09£30000-2014-1-0001 

Ms. Anita Pease 

Associate Director 

U.S. Environmental Protection Agency 

Office of Pesticide Programs 

Environmental Fate and Effects Division 

1200 Pennsylvania Ave., NW 

Washington, D.C. 20460 

f.O D - 2 2014 

Subject: Informal Consultation on the Proposed Registration of Silicon Dioxide and 

Silica Gel 

Dear Ms. Pease: 

This letter is in response to your February 10, 2014, email requesting the U .S . Fish and 

Wildlife Service's (Service) concurrence that the proposed registration of silicon dioxide 

and silica gel (Case No. 4081) is not likely to adversely affect any listed species or 

critical habitat pursuant to section 7 of the Endangered Species Act of 1973 (16 U.S.C. 

1531 -1544), as amended (ESA). This consultation is based on the provided 

Environmental Fate and Ecological Risk Assessment for the Registration of Silicon 

Dioxide and Silica Gel. 

The EPA is currently in the final stages of Registration Review for the active ingredients 

of silica gel and silicon dioxide. Silica gel was first registered for use in 1956 and silicon 

dioxide in 1960. Through Registration Review, EPA determines whether a pesticide 

continues to meet the Federal Insecticide, Fungicide and Rodenticide Act standard for 

registration. Silica gel is only registered for indoor uses, and therefore is not discussed 

further in this document. 

The EPA focused their risk assessment on silicon dioxide, in the form of diatomaceous 

earth (DE), which is currently registered for outdoor uses. Silicon dioxide is a biogenic 

form of silica, generally derived from DE deposits. The insecticidal mode of action is 

physical (desiccation) rather than toxicological. When used as an insecticide, DE kills 

insects by abrading and absorbing oils from the insect's exoskeleton, leading to the 

dehydration and death of the insect. DE must be applied in pure form in sufficient 

concentration to be effective. 
Ms. Anita Pease 

According to EPA's risk assessment, there are at least 24 products with outdoor uses 

containing DE as the active ingredient. These products are formulated as dusts or 

wettable powders and can be applied using hand or electric puffer dusters or liquid spray 

equipment. There is one DE product that may be applied by fixed winged aircraft on 

"unspecified field crops," but the application rate is limited to 0.625 lbs/acre and is 

thought to be a pesticide carrier rather than an efficacious component at that application 

rate (Konmic, 1998). The highest broadcast rate identified on the product labels is 83 lbs 

active ingredient/acre, though higher per acre rates are permissible for highly localized 

uses (e.g., crack and crevice). Use sites identified on product labels include agricultural 

crops (vegetables, fruits, grains, cotton, spices, tree nuts, tea), pastures, agricultural 

buildings and equipment, airports/landing fields, commercial animal kennels and sleeping 

quarters, commercial/institutional/industrial premises and equipment, golf course turf, 

household/domestic dwellings outdoor premises, ornamentals (ground cover, herbaceous 

plants, non-flowering plants, woody shrubs, and vines), shade trees, residential lawns and 

gardens, and refuse/solid waste containers. Although labeled for a wide variety of use 

sites, DE-based insecticides are most frequently applied to pests in homes and gardens, 

and in the protection of agricultural stored products (indoor use) (USEPA 2014). 

Some products are formulated in combination with other active ingredients [e.g., 

pyrethrins and piperonyl butoxide (PBO)] and are applied either as a wettable powder or 

as a dust when plants are wet. Pyrethrins are botanical insecticides derived from 

chrysanthemum flowers most commonly found in Australia and Africa. They work by 

altering nerve function, which causes paralysis in target insect pests, eventually resulting 

in death (EPA 2014). PBO acts as a synergist. Synergists are chemicals that primarily 

enhance the pesticidal properties of other active ingredients, such as pyrethrins and 

synthetic pyrethroids (EPA 2006). Although products containing these other active 

ingredients were not analyzed in EPA's risk assessment, EPA concluded that any 

synergistic effects with pyrethrins and/or PBO are not expected due to the inert nature of 

OE. 

In 1991, EPA completed a Reregistration Eligibility Decision on Silicon Dioxide and 

Silica Gel (EPA 1991 ). This assessment was used as the basis for EPA' s cWTent risk 

assessment. At the time, it was concluded that silicon dioxide and silica gel do not pose 

wrreasonable risks to the environment, including non-target organisms, at labeled use 

rates because they are chemically unreactive in the environment, occur naturally in 

various forms and are practically non-toxic to non-target organisms. 

Silicon dioxide is ubiquitous in the natural environment and a major component of most 

soils. Most of the silica in soils is in the crystalline form, which does not have 

insecticidal properties. However, most soils contain 2-3 percent amorphous silica, which 

does have insecticidal properties. The efficacy of DE, an amorphous form of silica, is 

limited in time and space (EPA 2014). DE is toxic to insects when it is highly pure, of 

uniform small particle size, and has a high oil absorption capacity (Korunic 1997). 

Therefore, DE loses its effectiveness when it gets wet, clumps together, or becomes 

contaminated with other substances (e.g., clay or other soil particles) (EPA 2014). Any 

sign]ficant drift of DE away from the application site would likely not be of a high 

2 
Ms. Anita Pease 

enough concentration to be efficacious. Aquatic systems are not considered to be of a 

concern because DE is not applied directly to water and diatoms are present in almost 

every aquatic system (EPA 2014). Runoff from the target area is expected to be 

dominated by naturally occurring silicon dioxide, and thus DE would be indistinguishable 

from soil particles, naturally occurring diatoms or sediment (deposited or suspended) 

(EPA 2014). Species affected by application of DE are expected to be terrestrial 

arthropods on the treated area. 

The EPA made the determination of no direct effect for all listed species except for 57 

terrestrial non-subterranean arthropods (Appendix A) that may be exposed to DE at the 

site of application. In addition, the EPA made the determination of may affect, not likely 

to adversely affect for indirect effects to terrestrial invertebrates, birds, terrestrial-phase 

amphibians and reptiles and mammals due to their reliance on insects as a food source. 

For the 57 non-subterranean terrestrial arthropods, EPA made the determination of may 

affect, not likely to adversely affect based on the following reasons: 

1. DE has a mechanical rather than toxic mode of action; therefore, the 

potential for an adverse effect is limited in time and space, to the treated 

area, not off-site, and to a short interval after application, since weathering 

renders DE inefficacious. Although the time to effective weathering in not 

quantified, it is expected to be no longer than to the next rainfall. 

2. DE is a naturally occurring substance, wide-spread in many soils in low 

concentrations. Thus, listed species are expected to be exposed to silica, 

and are presumably adapted to low exposure concentrations. 

3. It is uncertain whether individuals would visit treated areas, or remain on 

these areas during the time of application, due to the attendant human 

disturbance. 

4. DE is used in organic agriculture and by homeowners seeking less-toxic 

alternatives to conventional pesticides. To the degree that DE is used in 

place of conventional insecticides, EPA concludes that this compound is a 

much safer alternative to listed terrestrial invertebrates. 

Direct Effects 

After review of the 57 non-subterranean terrestrial arthropods identified by EPA, the 

Service concurs with EPA's determination of may affect, not likely to adversely affect for 

the registration and application of DE at appropriate use sites. The following summaries 

describe our rationale for our concurrence. 

American burying beetle 

The American burying beetle (Nicrophorus americanus) eats carrion and insects 

(USFWS 2008a). Habitat generally includes deciduous and evergreen forests, sru:ub 

habitat, riparian forests and grasslands. The prevailing theory of the beetle's declme, 

rmderway for nearly a century and a serious concern by the 1920s (Ratcliffe 1996), points 

to habitat loss, degradation and fragmentation leading to a corresponding decrease in 

suitable carrion (USFWS 1991, Sikes and Raithel 2002). As more and more l~d was 

developed or converted for agriculture and other uses, the resulting altered habitats 

3 
Ms. Anita Pease 

favored scavenging mammals and bird species that compete with carrion beetles for 

resources (USFWS 2008a). On the contemporary landscape, vegetation aspects of 

American burying beetle's habitat across large areas of the species' historic range, 

particularly east of the Mississippi River, are no longer suitable because of development, 

habitat conversion for agricultural crops, grazing, or alterations that preclude the presence 

of carrion resources required by the burying beetle to thrive (USFWS 2008a). Based on 

the available information, adult American burying beetles are highly unlikely to find 

suitable carrion at sites registered for DE use due to competition with scavenging 

mammals and bird species now relatively common at those use sites. Even if the burying 

beetle were to find suitable carrion at one of these use sites, it would have to co-occur 

with the timing of DE application and the Service believes that is highly improbable. 

Butterflies 

There are 24 species of listed butterflies for which EPA made the determination of may 

affect, not likely to adversely affect. These 24 species of butterflies share similar life 

history characteristics. These butterflies all occur in remnant native habitats and rely on 

one or several native host plants for larval development. Additionally, many of the adult 

forms rely on native nectar sources for food and are rarely found outside of their native 

habitat. In many cases, these native habitats are interspersed with agricultural lands or 

other human developments; however, it is highly unlikely that adults of these species 

would be found foraging far from their larval host plants. Based on the available 

information, it is highly improbable that the adults of these 24 species of butterflies 

would be found to forage in any of the DE registered use sites because they are unlikely 

to contain suitable nectar sources. 

Casey's June beetle 

Casey's June beetle (Dinacoma caseyi) distribution is confined to an area ofless than 800 

acres in southern Palm Springs, California (USFWS 2009a). Casey's June beetle habitat 

is typically associated with broad, gently sloping, depositional surfaces that form at the 

base of the Santa Rosa Mountains in the dry Coachella Valley region by the overlapping 

or converging of individual alluvial fans (bajada) (Bates and Jackson 1987). Casey's 

June beetles emerge from underground burrows sometime between late March and early 

June, with abundance peaks generally occurring in April and May (Duff 1990; Barrows 

1998). Females are always observed on the ground and are considered flightless (Duff 

1990; Hovore 1995; Hovore 2003). During the active flight season, males emerge from 

the ground and begin flying near dusk (Hovore 2003). Males flying in the area are 

attracted to females by pheromones (Cornett 2004). Males are reported to fly back and 

forth or crawl on the ground where a female beetle has been detected (Duff 1990). After 

mating, females return to their burrows or dig a new burrow and deposit eggs. Casey's 

June beetle continues to be impacted by threats to the individual including loss of 

individuals due to attraction to swimming pools and light sources (USFWS 2013a). 

Lights attract male beetles away from habitat and females resulting in wasted energy, and 

they are frequently trapped and die in lights that have broken covers (K. Osborne 2012, 

pers. comm., in USFWS 2013a). Based on available information, designated use sites 

(e.g., home properties), are no longer suitable habitat for Casey's June beetles. Females 

do not fly and would not be anticipated to found outside their preferred habitat. Although 

4 
Ms. Anita Pease 

males do fly in search of females, and have been attracted to lights, it is highly unlikely 

that they would be attracted to DE treated use sites since females would not be present. 

Delhi sands flower-loving fly 

The Delhi Sands flower-loving fly (Rhaphiomidas terminatus abdominalisis) is generally 

found in areas containing Delhi fine sands soil type (USFWS 2008b ). Oviposition (egglaying) occurs within loose, sandy soils in late summer months and may primarily occur 

near telegraph weed (Rogers and Mattoni 1993; Kingsley 1996). Larval stages develop 

completely underground and emerge as adults from July through September. Adults are 

most active during the wannest, sunniest parts of the day, and both males and females 

extract nectar from California buckwheat and other plants (Kingsley 1996). Based on the 

Delhi sands flower-loving fly 's association with specific habitats and nectar sources, it is 

highly unlikely that adult flies would be attracted to or exposed to DE treated use sites. 

Delta green ground beetle 

Currently, the delta green ground beetle (Elaphrus viridis) is only known to occur at the 

Jepson Prairie in Solano County, California (USFWS 2009b). It is believed that adults 

emerge from diapause and females lay their eggs in early winter, and then the species 

disappears from view until active adults reappear the following winter (USFWS 2009b ). 

It is also believed that, as vernal pool habitats become dry, the beetle larvae crawl into 

cracks in the soil, and survive the hot, dry summer and fall as diapausing pupae (USFWS 

2009b). The beetle is typically found along the margins of vernal pools and in bare areas 

along trails and roadsides, where individuals often hide in cracks in the mud and under 

low-growing vegetation (USFWS 2009b). Based on the delta green ground beetles 

association with vernal pool and prairie habitats, it is highly unlikely that adult beetles 

would be attracted to or exposed to DE treated use sites. 

Hawaiian damselflies 

The five listed Hawaiian damselflies are all associated with stream and riparian habitats. 

In four of the five species, the immature larval stages (naiads) are aquatic. The flying 

earwig Hawaiian damselfly (Megalagrion nesiotes), thought to be terrestrial or semiterrestrial, occupies habitat along a single east Maui stream on the adjacent steep, moist, 

riparian talus slope. Adults of the five Hawaiian damselflies rarely venture far from their 

breeding sites or outside of the riparian corridor. Based on the available information, the 

Service concludes that it is highly improbable that the adults of these five species of 

damselflies would be exposed to DE registered use sites. 

Hawaiian pomace and picture-wing flies 

The 14 listed Hawaiian pomace and picture-wing flies are all associated with larval host 

plants and are restricted to the natural distribution of those plants. In most cases, the 

larvae feed on the decaying stems or bark of their associated host plants. In one case, 

Drosophila musaphiliathe, the female of the species lay eggs upon ~oa (Acac~a ~o~), and 

the larvae develop in a slime flux that occasionally appears on certain trees with mJured 

plant tissue and seeping sap (Montgomery 1975). Based on the available inf?nnatio~, it 

is highly improbable that the adults of these thirteen species of pomace and p1cture-wmg 

flies would forage on plants other than those found in their native habitat. 

5 
Ms. Anita Pease 

Hine's Emerald Dragonfly 

The Hine's emerald dragonfly (Somatochlora hineana) is currently found in Illinois, 

Michigan, Missouri and Wisconsin (USFWS 2013b). The dragonfly is apparently 

restricted to wetland habitats characterized by thin soils over dolomite bedrock with 

marshes, seeps, and sedge meadows (USFWS 200 I). Other components of this wetland 

complex habitat include open, vegetated areas and nearby or adjacent forest edge 

(USFWS 2001 ). Areas of open vegetation serve as places to forage, while forests, trees, 

or shrubs provide shaded areas for the dragonfly to perch and roost (USFWS 2001). The 

life cycle of Hine's emerald dragonfly is similar to most dragonflies in that it is comprised 

of the following stages: aquatic egg, aquatic larva and a terrestrial/aerial adult (Corbet 

1962). Fully adult Hine's emerald dragonflies can live at least 14 days (Soluk et al. 

1996), and may live four to six weeks (Mierzwa et al. 1995). Most dragonfly adults are 

general predators throughout their entire life cycle, feeding primarily on insects they can 

capture while flying (USFWS 2001). Adult Hine's emerald dragonflies capture aerial 

prey in flight and have been observed foraging on small dipterans (gnats and other twowinged flies) (Vogt and Cashatt 1994). Typically, flight courses are irregular and occur 

over herbaceous habitat, often near clusters of shrubs or the forest edge (Cashatt and 

Vogt 1990; Vogt and Cashatt 1990, 1994; Nuzzo 1995). Hine's emerald dragonflies 

forage over meadows, successional fields, narrow roads and along Lake Michigan (Vogt 

and Cashatt 1994 ). In contrast to feeding flights, male territorial patrols are concentrated 

near aquatic habitats. The Hine's emerald dragonfly spends the majority of its life within 

the aquatic community and adjacent native upland habitat. Although foraging adults may 

take short ventures outside of this habitat, it is unlikely that they would rest or perch 

within a DE treated use site. 

Mount Hermon June beetle 

The Mount Hermon June beetle (Polyphy/la barbata) is a small, dark-brown scarab 

beetle, with light, irregular and broken stripes on the elytra (USFWS 2009). Seasonal 

activity in this species occurs between May and August and lasts approximately 12 weeks 

(Arnold 2003, 2004a, 2005, 2006, 2007). Females are flightless and emerge from 

burrows only to mate, after which they immediately return underground. Activity in this 

species is strictly crepuscular, with males emerging at dusk and emitting a crackling 

sound as they fly low over ground or brush likely following pheromonal cues to find 

females for mating (Arnold 2004b). Little is known about the entirety of the life cycle; 

however, Arnold (2004b) believes that it likely is a 2- to 3-year life cycle, with the 

majority of time spent underground. Arnold (2000, 2001) also believes, based on markrecapture studies, that adult males live for no longer than one week. It is likely, 

considering their short lifespan, that adult males do not feed, focusing instead solely on 

reproduction over consecutive days until their energy reserves are expended (Hazeltine 

1993). Based on available information, designated use sites (e.g., home properties), are 

no longer suitable habitat for Mount Hermon June beetles. Considering the likelihood 

that male beetles do not forage, but instead focus solely on seeking out females to mate, it 

is highly improbable that males of this species would be attracted to or exposed to DE 

treated use sites. 

6 
Ms. Anita Pease 

Sphinx moths 

There are two listed species of sphinx moths. One is located in Hawaii and one in 

California. Both sphinx moths share vary similar life history traits that include reliance 

on native host plants for egg laying and larval food and suitable soil beneath the host 

plants that allows larvae to burrow and construct shallow pupal chambers. In Hawaii, the 

Blackburn's sphinx moth (Manduca blackburni) larvae have been found to feed upon the 

non-native tree tobacco (Nicotiana glauca). Based on the available information, it is 

highly improbable that the adults of these two species of sphinx moths would be found to 

forage in any of the DE registered use sites. 

Tiger beetles 

The four listed tiger beetles are all habitat specialists. These beetles rely on specific soils 

(e.g., sandy deposits, moist salt flats, sandy clay) to construct larval burrows. For 

example, the Ohlone tiger beetle (Cicindela oh/one) is endemic to Santa Cruz County, 

California, where it is known only from coastal terraces supporting patches of native 

grassland habitat (Freitag et al. 1993). Adult Ohlone tiger beetles are typically found 

along trails or barren areas among low, sparse vegetation within the grassland habitat 

(USFWS 2009c ). Ohlone tiger beetles require these open areas for construction of larval 

burrows, thermoregulation, and foraging (USFWS 2009c). Both adults and larvae of 

tiger beetles feed exclusively on other arthropods. Based on the tiger beetles dependence 

on specific endemic habitats and the fact that they forage on arthropods within those 

habitats, it is highly improbable that adult tiger beetles would be attracted to or exposed 

to DE treated use sites. 

Valley elderberry longhorn beetle 

The valley elderberry longhorn beetle (Desmocerus californicus dimorphus) is endemic 

to the Central Valley of California. The beetle is found only in association with its host 

plant, elderberry (Sambucus sp.) (USFWS 2006). Adults feed on the foliage and perhaps 

flowers and are present from March through early July (USFWS 2006). Based on the 

valley elderberry longhorn beetle's association with elderberry bushes, it is highly 

improbably that the beetle would forage on plants other than elderberry. 

Zayante band-winged grasshopper 

The Zayante band-winged grasshopper (Trimerotropis infantilis) is known only from the 

Zayante sandhills of Santa Cruz County, California. The adult flight activity period of 

the grasshopper extends from July until the first ground-soaking rains of the winter 

(usually around early Nov.) (Arnold 2004e). Adults may live for more than a month and 

usually are found either directly on sandy soil or on the foliage of the silver bush lupine 

(Lupinus albifrons), which makes up over 60 percent of their diet (Chu 2002). Females 

oviposit eggs directly into loose, sandy soil. The eggs over-winter in the soil, and 

nymphs begin to appear in May, with the first adults appearing in July (USFWS 2009d). 

Based on the Zayante band-winged grasshopper's association with sandy soils and silver 

bush lupine, it is highly improbable that adult grasshoppers would be attracted to or 

exposed to DE treated use sites. 

7 
Ms. Anita Pease 

In summary, we concur with your detennination that the use of DE at registered use sites 

may affect, but is not likely to adversely affect the aforementioned insect species. The 

potential for these insect species to come into contact with DE is extremely unlikely, and 

therefore, we consider the risk to be discountable. 

Indirect Effects 

The Service concurs with EPA's determination of may affect, not likely to adversely 

affect for indirect effects for terrestrial invertebrates, birds, terrestrial-phase amphibians 

and reptiles and mammals due to their reliance on insects as a food source. The reduction 

in available food source (i.e., insects), for the above listed taxa, would be insignificant 

and discountable due to the highly localized and short-term nature in that reduction of 

food at DE registered use sites. In addition, it is highly improbable that those listed taxa, 

with the exception of birds and possibly some amphibians, would even forage in DE 

registered use sites. 

This concludes informal consultation on the national registration of silicon dioxide and 

silica gel. Therefore, unless new information reveals effects of the proposed action that 

may affect listed species in a manner or to an extent not considered, or a new species is 

listed, no further action pursuant to the Act is necessary. If you have any questions 

please contact Keith Paul of my office at (703) 358-2675. 

Attachments 

Patrice Ashfield 

Chief, Branch of Consultation and Habitat 

Conservation Plans, Ecological Services 

8 
Ms. Anita Pease 

Literature Cited 

Arnold, R. A. 2000. Monitoring report for the Mount Hermon June beetle at the Quail 

Hollow Quarry in 2000. Report prepared for: Granite Rock, Watsonville, 

California; County of Santa Cruz Planning Department, Santa Cruz, California; 

U.S. Fish and Wildlife Service, Region I Eastside Federal Complex, Portland, 

Oregon; California Department of Fish and Game, Yountville, California. 

Arnold, R. A. 2001. 2001 monitoring report for the Mount Hermon June beetle at 

Hanson Aggregates' Felton Quarry. Report prepared for: Hanson Aggregates 

Mid-Pacific Region, Pleasanton, California; U.S. Fish and Wildlife Service, 

Region I Eastside Federal Complex, Portland, Oregon; U.S. Fish and Wildlife 

Service, Ventura Field Office, Ventura, California; Center for Natural Land 

Management, Fallbrook, California; County of Santa Cruz Planning Department, 

Santa Cruz, California. 

Arnold, R. A. 2003. 2003 monitoring report for the Mount Hermon June beetle at 

Hanson Aggregates' Felton Quarry. Report prepared for: Hanson Aggregates 

Mid-Pacific Region, Pleasanton, California; U.S. Fish and Wildlife Service, 

Region 1 Eastside Federal Complex, Portland, Oregon; U.S. Fish and Wildlife 

Service, Ventura Field Office, Ventura, California; Center for Natural Land 

Management, Fallbrook, California; County of Santa Cruz Planning Department, 

Santa Cruz, California. 

Arnold, R. A. 2004a. 2004 monitoring report for the Zayante band winged grasshopper 

at Hanson Aggregates' Felton Quarry. Report submitted to Hanson Aggregates 

Mid-Pacific Region, Pleasanton, California; U.S. Fish and Wildlife Service, 

Region 1 Eastside Federal Complex, Portland, Oregon; U.S. Fish and Wildlife 

Service, Ventura Field Office, Ventura, California; Center for Natural Land 

Management, Fall brook, California; County of Santa Cruz Planning Department, 

Santa Cruz, California. 

Arnold, R. A. 2004b. Zayante band winged grasshopper. Pages 81-91 in J.M. McGraw 

(author), Sand.hills conservation and management plan: a strategy for preserving 

native biodiversity in the Santa Cruz sandhills. Report submitted to the Land 

Trust of Santa Cruz County, Santa Cruz, California. 310 pp. 

Arnold, R. A. 2005. 2005 monitoring report for the Mount Hermon June beetle at 

Hanson Aggregates' Felton Quarry. Report prepared for: Hanson Aggregates 

Mid-Pacific Region, Pleasanton, California; U.S. Fish and Wildlife Service, 

Region l Eastside Federal Complex, Portland, Oregon; U.S. Fish and Wildlife 

Service, Ventura Field Office, Ventura, California; Center for Natural Land 

Management, Fall brook, California; County of Santa Cruz Planning Department, 

Santa Cruz, California. 

Arnold, R. A. 2006. 2006 monitoring report for the Mount Hermon June beetle at 

Granite Rock's Quail Hollow Quarry. Report prepared for: Granite Rock, 

Watsonville, California; County of Santa Cruz Planning Department, Santa Cruz, 

9 
Ms. Anita Pease 

California; U.S. Fish and Wildlife Service, Region 1 Eastside Federal Complex, 

Portland, Oregon; California Department of Fish and Game, Yountville, 

California. 

Arnold, R. A. 2007. Monitoring report for the Zayante band winged grasshopper at the 

Quail Hollow Quarry in 2007. Report submitted to Granite Rock, Watsonville, 

California; County of Santa Cruz Planning Department, Santa Cruz, California; 

U.S. Fish and Wildlife Service, Region 1 Eastside Federal Complex, Portland, 

Oregon; California Department of Fish and Game, Yountville, California. 

Barrows, C. 1998. Results of Searches for Casey's June Beetle, Spring 1998. 

Unspecified submission recipient. 

Bates, R. L. and J.A Jackson. 1987. Glossary of Geology. American Geological 

Institute, Alexandria, Virginia. 788 pp. 

Cashatt, E.D., and T.E. Vogt. 1990. The Illinois 1990 status survey for the Ohio emerald 

dragonfly (Somatochlora hineana Williamson). Report to the U.S. Fish and 

Wildlife Service. Illinois State Museum, Springfield, Illinois. 20 p. 

Chu, J. 2002. Diet for an Endangered Insect: What Does the Zayante Band-Winged 

Grasshopper Eat? Master Thesis, Department of Environmental Studies, San Jose 

State University. 

Corbet, P.S. 1962. A Biology of Dragonflies. H.F. & G. Witherby Ltd., facsimile 

reprint 1983 by E.W. Classey Ltd., Ox on, United Kingdom. 24 7 pp. 

Cornett, J.W. 2004. Analysis of the Distribution and Abundance of the Casey's June 

Beetle (Dinacoma caseyi) in Palm Springs, California, prepared for Smoke Tree 

Ranch, Inc., Palm Springs, California. 

Duff, R. 1990. Dinacoma caseyi: Current Status of Endangered Species. Unspecified 

submission recipient. 

Freitag, R., D.H. Kavanaugh, and R. Morgan. 1993. A new species of Cicindela 

(Cicindela) (Coleoptera: Carabidae: Cicindelini) from remnant native grassland in 

Santa Cruz County, California. Coleopterists Bulletin, 46: 113-120. 

Haziltine, W. 1993. Distribution of the scarab beetle, Polyphylla barbata Cazier. 5 

pages and 4 figures. Unpublished report, dated July 13. Oroville, California. 

Hovore, F. 1995. Report of field surveys: Coachella Valley Multi-species HCP, 

Invertebrates - Palm Springs June beetle (Dinacoma caseyi). Unspecified 

submission recipient. 

Hovore, F. 2003 . Report of focused surveys for Casey's June beetle: Smoketree Ranch 

and vicinity, prepared for Krieger & Stewart, Inc., Riverside, California. 

10 
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Kingsley, K.J. 1996. Behavior of the Delhi Sands flower-loving fly (Diptera, Mydidae ), 

a little-known endangered species. Annals of the Entomological Society of 

America 89:883-891. 

Korunic, Z., 1997. Rapid assessment of the insecticidal value of diatomaceous earths 

without conducting bioassays. Journal of Stored Products Research 3, 219-229. 

Korunic, Z. 1998. Diatomaceous earths, a group of natural insecticides. Journal of 

Stored Products Reasearch. 34:2-3. pp87-97. 

Mierzwa, K.S., A.P. Smyth, and E.D. Cashatt. 1995. Population dynamics of the Hine's 

emerald dragonfly (Somatochlora hineana) in Illinois. In K.S. Mierzwa, 

(editors). The Hine's emerald dragonfly in Illinois: an assessment of population 

dynamics and habitat use. TAMS Consultants, Inc., Chicago, Illinois. P 9-48. 

Montgomery, S.L. 1975. Comparative breeding site ecology and the adaptive radiation 

of picture-winged Drosophila (Diptera: Drosophilidae) in Hawaii. Proceedings of 

the Hawaiian Entomological Society 12:65-103. 

Nl1Zzo, V.A. 1995. Hine's emerald dragonfly (Somatochlora hineana) breeding and 

foraging habitat at three sites in the lower Des Plaines Rivers Valley, Illinois. In 

K.S. Mierzwa, (editors). The Hine's emerald dragonfly in Illinois: An assessment 

of population dynamics and habitat use. TAMS Consultants, Inc., Chicago, 

Illinois. p 49-75. 

Ratcliffe, B .C . 1996. The carrion beetles (Coleoptera: Silphidae) of Nebraska. Bulletin 

of the University of Nebraska State Museum. Vol. 13, 100 p. 

Rogers, R. and M. Mattoni. 1993. Observations on the narural history and conservation 

biology of the giant flower-loving flies, Rhaphiomidas (Diptera: Apioceridae). 

Dipterological Research 4(1-2):21-34. 

Sikes, D.S. and Raithel, R.J. 2002. A review of hypothesis of decline of the endangered 

American burying beetle (Silphidae: Nicrophorus americanus Olivier). Journal of 

Insect Conservation 6: 103-113> 

Soluk, D.A., B.J. Swisher, and D.S. Zercher. 1996. The ecology ofHine's emerald 

dragonfly (Somatochlora hineana): monitoring populations and determining 

patterns of habitat use in the Des Plaines River valley. Activity summary and 

report of preliminary results (January-August 1996). Illinois Natural History 

Survey, Champaign, Illinois. 35 p. 

U.S. Environmental Protection Agency. 1991. Reregistration Eligibility Docwnent, 

Silicon Dioxide and Silica Gel (Case No. 4081). Office of Pesticide Programs, 

Specia] Review and Registration Division, Washington, D.C. 32 p. 

U.S. Environmental Protection Agency. 2006. Reregistration Eligibility Decision 

Document for Piperonyl Butoxide (PBO). United States Environmental 

Protection Agency, Office of Prevention, Pesticides and Toxic Substances. 

11 
Ms. Anita Pease 

U.S. Environmental Protection Agency. 2014. Environmental Fate and Ecological 

Effects Risk Assessment for the Registration for the Registration Review of Silica 

(Case No. 4081). U.S. Environmental Protection Agency, Office of Chemical 

Safety and Pollution Prevention, Environmental Fate and Effects Division, 

Washington, D.C. 97 p. 

U.S. Fish and Wildlife Service. 1991. American Burying Beetle (Nicrophorus 

americanus) Recovery Plan. Newton Comer, Massachusetts. 62 p. 

U.S. Fish and Wildlife Service. 2001. Recovery Plan for the Hine's Emerald Dragonfly 

(Somatochlora hineana Williamson). U.S. Fish and Wildlife Service, Region 3, 

Fort Snelling, Minnesota. September 2001. 133 p. 

U.S. Fish and Wildlife Service. 2006. Five-year Review: Valley elderberry longhorn 

beetle (Desmocerus ca/ifornicus dimorphus). U.S. Fish and Wildlife Service, 

Sacramento Fish and Wildlife Office, Sacramento, California. September 2006. 

30p. 

U.S. Fish and Wildlife Service. 2008a. Five-year Review: American Burying Beetle 

(Nicrophorus americanus). U.S. Fish and Wildlife Service, New England Field 

Office, Concord, New Hampshire. March 2008. 53 p. 

U.S. Fish and Wildlife Service. 2008b. Five-year Review: Delhi Sands Flower-loving 

Fly (Rhaphiomidas terminatus abdominalis). U.S. Fish and Wildlife Service, 

Carlsbad Fish and Wildlife Office, Carlsbad, California. March 2008. 30 p. 

U.S. Fish and Wildlife Service. 2009a. Endangered and Threatened Wildlife and Plants; 

Listing Casey's June Beetle (Dinacoma caseyl) as Endangered and Designation of 

Critical Habitat. Federal Register 74:32857-32875. 

U.S. Fish and Wildlife Service. 2009b. Five-year Review; Delta Green Ground Beetle 

(Elaphrus viridis). U.S. Fish and Wildlife Service, Sacramento Fish and Wildlife 

Office, Sacramento, California. January 2009. 29 p. 

U.S. Fish and Wildlife Service. 2009c. Five-year Review; Ohlone tiger beetle 

(Cicindela oh/one). U.S. Fish and Wildlife Service, Ventura Fish and Wildlife 

Office, Ventura, California. November 2009. 27 p. 

U.S. Fish and Wildlife Service. 2009d. Five-year Review: Zayante band-winged 

grasshopper (Trimerotropis infantilis) and Mount Hermon June beetle (Polyphylla 

barbata). U.S. Fish and Wildlife Service, Ventura Fish and Wildlife Office, 

Ventura, California. August 2009. 33 p. 

U.S. Fish and Wildlife Service. 2013a. Recovery Outline for Casey's June Beetle 

(Dinacoma caseyi). U.S. Fish and Wildlife Service, Carlsbad Fish and Wildlife 

Office, Carlsbad, California. March 2013. 21 p. 

12 
Ms. Anita Pease 

U.S. Fish and Wildlife Service. 2013b. Five-year Review: Hine's Emerald Dragonfly 

(Somatochlora hineana). U.S. Fish and Wildlife Service, Chicago Ecological 

Services Field Office, Barrington, Illinois. May 2013. 50 p. 

Vogt, T.E., and E.D. Cashatt. 1990. The Wisconsin 1990 status survey for the Ohio 

emerald dragonfly (Somatochlora hineana Williamson). Report to the U.S. Fish 

and Wildlife Service. Illinois State Museum, Springfield, Illinois. 9 p. 

Vogt, T.E., and E.D. Cashatt. 1994. Distribution, habitat, and field biology of 

Somatoch/ora hineana (Odonata: Corduliidae). Annals of the Entomological 

Society of America 87(5): 599-603. 
Ms. Anita Pease 14 

Annendix A. EPA's and FWS' Determinations for Listed Terrestrial Arthropods 

Common Name Scientific Name Medium Taxa EPA FWS 

Determination Determination 

American burying beetle Nicrophoru:r americanu:r Terrestrial Insect NLAA Concur 

Bay checkerspot butterfly Euphydryas editha bayensis Terrestrial Insect NLAA Concur 

Bee Creek Cave harvestman Texella redde/li Subterraneous Arachnid No effect No effect 

Behrcn's silvcrspot butterfly Speyeria zerene behrensii Terrestrial Insect NLAA Concur 

Blackburn's sphinx moth Manduca blackburni Terrestrial Insect NLAA Concur 

Blackline Hawaiian damselfly ·Mega/agrion nigrohamatum Terrestrial Insect NLAA Concur 

niPro/ineatum 

Bone Cave harvestman Texe/la reye:ri Subterraneous Arachnid No effect No effect 

Brak.en Bat Cave Meshweaver Cicurina venii Subterraneous Arachnid No effect No effect 

Callippe silverspot butterfly Speyeria callippe cal/ippe Terrestrial Insect NLAA Concur 

Carson wandering skipper P:reudocopaeodeseunu:r Terrestrial Insect NLAA Concur 

obscuru:r 

Caseys June Beetle Dinacoma caseyi Terrestrial Insect NLAA Concur 

Coffin Cave mold beetle Balrisodes texanu:r Subterraneous Insect No effect No effect 

Cokendolpher Cave Harvestman Texe/la colcendo/pheri Subterraneous Arachnid No effect No effect 

Comal Springs dryopid beetle Stygoparnu:r coma/ensis Freshwater Insect No effect No effect 

Comal Spring.s riffle beetle Hetere/mis coma/ensis Freshwater Insect No effect No effect 

Crimson Hawaiian damselfly Mega/agrion leptodemus Terrestrial Insect NLAA Concur 

Delhi Sands flower-loving fly Rhaphiomidas termiootus Terrestrial Insect NLAA Concur 

abdominal is 

Delta green ground beetle Elaphru:r viridis Vernal Pool Insect NLAA Concur 

El Segundo blue butterfly Euphi/otes banoider al/yni Terrestrial Insect NLAA Concur 

Fender's blue butterfly Jcaricia icarioides fenderi T errcstrial Insect NLAA Concur 

Florida leafwing butterfly Anaea troglodytaj/oridali:r Terrestrial Insect NLAA Concur 

Flying earwig Hawaiian Megalagrion ne:riote:r Terrestrial Insect NLAA Concur 

damselflv 

Government Canyon Bat Cave Cicurina vespera Subterrancous Arachnid No effect No effect 

Meshweaver 

Government Canyon Bat Cave Neo/eptoneta microps Subtcrrancous Arachnid No effect No effect 

Soider 

Hawaiian picture-wing fly Drosophila sharpi Terrestrial Insect NLAA Concur 

Hawaiian picture-wing fly Drosophila digres:ra Terrestrial Insect NLAA Concur 

Helotes mold beetle Batrisodes venyivi Subterraneous Insect No effect No effect 

Hine's emerald dragonfly Somatoch/ora hineana Terrestrial Insect NLAA Concur 

Hungerford's crawling water Brychius hungerfordi Freshwater Insect No effect No effect 

Beetle 

Kamer blue butterfly Lycaeides me/issa samuelis Terrestrial Insect NLAA Concur 

Kauai cave wolf spider Ade/ocosa anop:r Terrestrial Arachnid No effect No effect 

Kem primrose sphinx moth Euproserpinu:r euterpe Terrestrial Insect NLAA Concur 

Kretschmarr Cave mold beetle Texamaurops redde/li Subterrancous Insect No effect No effect 

Laguna Mountains skipper J>yrgus rura/i:r /agunae Terrestrial Insect No effect No effect 
Ms. Anita Pease 15 

Lange's metalmark butterfly Apodemia mormo langei Terrestrial Insect NLAA Concur 

Lotis blue butterfly Lycaeides argyrognomon /otis Terrestrial Insect NLAA Concur 

Media's Cave Meshweaver Cicurina madla Subterraneous Arachnid No effect No effect 

Miami Blue Butterfly Cyc/argus (~Hemiargus) Terrestrial Insect NLAA Concur 

thomasi bethunebakeri 

Mission blue butterfly lcarfcia icarioides Terrestrial Insect NLAA Concur 

missiommsis 

Mitchell's satyr Butterfly Neonympha milchel/ii Terrestrial Insect NLAA Concur 

milchel/ii 

Mount Charleston blue butterfly Plebejus sharia Terrestrial Insect NLAA Concur 

chares/onensis 

Mount Hermon June beetle Polyplryl/a barbara Subterraneous Insect NLAA Concur 

Myrtle's silverspot butterfly Speyeria zerene myrlleae Terrestrial .Insect NLAA Concur 

Northeastern beach tiger beetle Cicinde/a dorsalis dorsa/is Terrestrial Insect NLAA Concur 

Oceanic Hawaiian damselfly Megalagrion oceanicum Terrestrial Insect NLAA Concur 

Oh lone tiger beetle Cicindela oh/one Terrestrial Insect NLAA Concur 

Oregon silverspot butterfly Speyeria zerene hippolyta Terrestrial Insect NLAA Concur 

Pacific Hawaiian damselfly Megalagrion pacificum Terrestrial Insect NLAA Concur 

Palos Verdes blue butterfly G/aucopsyche /ygdamus Terrestrial Insect NLAA Concur 

oafasverdesensis 

Pawnee montane skipper Hesperia leonardus monlana Terrestrial Insect NLAA Concur 

Puritan tiger beetle Cicindefa puritana Coastal Insect NLAA Concur 

Quino checkerspot butterfly Euphydryas edilha quino (=E. Terrestrial Insect NLAA Concur 

e. wriKhti) 

Robber Baron Cave Meshweaver Cicurina baronia Subterraneous Arachnid No effect No effect 

Saint Francis' satyr butterfly Neonympha mitchel/ii Terrestrial Insect NLAA Concur 

francisci 

Salt Creek Tiger beetle Cicindela nevadica Terrestrial Insect NLAA Concur 

lincolniana 

San Bruno elfin butterfly Caflophrys mossii bayensis Terrestrial Insect NLAA Concur 

Schaus swallowtail butterfly Heraclides aristodemus Terrestrial Insect NLAA Concur 

oonceanu.s 

Smith's blue butterfly Eupliifotes enople:r :rmithi Terrcstrl al fnsect NLAA Concur 

Spruce-fir moss spider Microhexura montivaga T errcstrial Arachnid No effect No effect 

Taylor's Chcckerspot butterfly Euphydryas edilha tay/ori Terrestrial Insect NLAA Concur 

TDo.tb Cav.c grolllld b~ .R.hmJ.i.nJ! pun.phone Subterraneous Insect No effect No effect 

Tooth Cave pseudoscorpion Tarlarocreagris texana Subterraneous Arachnid No effect No effect 

Tooth Cave Spider leptoneta myopica Subterraneous Arachnid No effect No effect 

Uncompahgre fritillary butterfly Bo/oria acrocnema Terrestrial Insect No effect No effect 

Unnamed ground beetle Rhadine infernafis Subterraneous Insect No effect No effect 

Unnamed ground beetle Rhadine exilis Subtcrraneous Insect No effect No effect 

Unnamed ground beetle Drosophila montgomeryi Terrestrial Insect NLAA Concur 

Unnamed ground beetle Drmophila differens Terrestrial Insect NLAA Concur 

Unnamed ground beetle Drosophila ochrobasis Terrestrial Insect NLAA Concur 

Unnamed ground beetle Drosophila hemipeza Terrestrial Insect NLAA Concur 

Unnamed ground beetle Drosophifa tarpliytricliia rcrrestn'al Insecr NLAA Concur 
Ms. Anita Pease 16 

Unnamed ground beetle Drosophila substenoptera Terrestrial Insect NLAA Concur 

Unnamed ground beetle Drosophila obatai Terrestrial Insect NLAA Concur 

Unnamed ground beetle Drosophila neoclavisetae Terrestrial Insect NLAA Concur 

Unnamed ground beetle Drosophila muf/i Terrestrial Insect NLAA Concur 

Unnamed ground beetle Drosophila heteroneura Terrestrial Insect NLAA Concur 

Unnamed ground beetle Drosophila aglaia Terrestrial Insect NLAA Concur 

Unnamed ground beetle Drosophila musaphilia Terrestrial Insect NLAA Concur 

Valley elderberry longhorn beetle Desmocerus californicus Terrestrial Insect NLAA Concur 

dimorohus 

Zayante band-winged grasshopper Trimerotropis infantilis Terrestrial Insect NLAA Concur 
United States Department of the Interior 

FISH AND WILDLIFE SERVICE 

In Reply Refer To: 

FWS/ AES/DER/BCH/059656 

09£30000-20 l 4-I-0001 

Ms. Anita Pease 

Associate Director 

U.S. Environmental Protection Agency 

Office of Pesticide Programs 

Environmental Fate and Effects Division 

1200 Pennsylvania Ave., NW 

Washington, D.C. 20460 . 

Washington, D.C. 20240 

~~\ ~ - g 2015 

Subject: Review of Informal Consultation on the Proposed Registration of 

Silicon Dioxide and Silica Gel for Two Butterfly Species 

Dear Ms. Pease: 

Thank you for your letter dated February l 0, 2015, requesting our concurrence that the continued 

registration of silicon dioxide (as diatomaceous earth) (DE) and silica gel (Case No. 408 I) is not 

likely to adversely affect the Fender's Blue butterfly (lcaricia icarioides fenderi) nor the 

Taylor's Checkerspot butterfly (Euphydryas editha taylori) pursuant to section 7 of the 

Endangered Species Act of 1973 (16 U.S .C. 1531 -1544), as amended (ESA). 

On April 2, 2014, the U.S. Fish and Wildlife Service (Service) issued a letter of concurrence with 

the Environmental Protection Agency's (EPA) determination of "may affect, not likely to 

adversely affect" for direct effects on 57 non-subterranean terrestrial arthropods. The Service 

also concurred with EPA's determination of"may affect, not likely to adversely affect" for 

indirect effects for terrestrial invertebrates, birds, terrestrial-phase amphibians, reptiles and 

mammals. Subsequent to the issuance of our letter of concurrence, our Oregon Fish and Wildlife 

Office highlighted potential concerns for specific use sites (e.g., pasture, vineyards) for the two 

aforementioned listed butterfly species in the Willamette Valley. 

To address this concern, EPA and the Service held several follow-up discussions to explore 

potential effects to these two butterfly species. In Oregon, there are currently no approved state 

labels for the use of DE in pastures or vineyards; however, these use sites may be approved over 

the course of the 15-year registration action. Your team spent a considerable amount of time 

conducting additional research regarding the potential impact of DE to insects and we appreciate 

the additional information you submitted. 
Ms. Anita Pease 2 

Based on this additional review of information and requirements, you confirmed your original 

determination of "may affect, not likely to adversely affect" for the two listed butterfly species 

due to the following: I) the existence of state-level pollinator protection requirements for DE, 

which are triggered by a state decision to register DE for a new use (via a section 18 or 24c 

label), and similar guidance available through other Extension Services; and, 2) on additional 

data showing low toxicity of DE to bees (as a surrogate for butterflies) at rates exceeding current 

application levels. Based on the information provided by EPA, the Service reaffirms our 

concurrence with your determination of "may affect, not likely to adversely affect" the Fender's 

Blue and Taylor's checkerspot butterflies. 

The Service greatly appreciates the additional effort put forth by EPA to address our concerns on 

this matter and the supplemental information provided on the national registration of silicon 

dioxide and silica gel. Therefore, unless new information reveals effects of the proposed action 

that may affect listed species in a manner or to an extent not considered, or a new species is 

listed, no further action pursuant to the ESA is necessary. If you have any questions please 

contact Keith Paul of my office at (703) 358-2675. 

Ro( Craig Aubrey 

.....- Chief, Division of Environmental Review, 

Ecological Services