Docket Number EPA

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, www.regulations.gov Interim Registration Review Decision for Silica Gel and Silicon Dioxide

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### Table of Contents

Contents

I. Introduction

................................ ................................ ................................ ............................... 2

II. Use and Usage

................................ ................................ ................................ ........................... 4

III. Scientific Assessments

................................ ................................ ................................ .............. 4

A. Human Health Assessment

................................ ................................ ............................ 4

Hazard Characterization and Dietary Risk

................................ ................................ .... 4

Residential and Occupational Exposure

................................ ................................ ........ 4

Aggregate Exposure and Risks

................................ ................................ ...................... 4

Food Tolerances

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

Human Incidents

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

B. Environmental Assessment

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

Environmental Fate and Exposure

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

Ecological Risk Conclusion

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

Endangered Species Assessment

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

Ecological Incidents

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

C. Endocrine Disruptor Screening Program

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

IV. Interim Registration Review Decision

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

V. Next Steps and Timeline

................................ ................................ ................................ ....... 10

VI

. Appendix: Informal Endangered Species Consultation

................................ ........................ 10Docket Number EPA

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### I. Introduction

This document is the Environmental Protection Agency’s (EPA or the Agency ) Interim Registration Review Decision for silica gel (PC code 072602) and silicon dioxide (PC code

07260 5 ), which are commonly referred to as: the silicates, silica silicates or diatomaceous earth (DE)

, and is being issued pursuant to 40 CFR sections 155.56 and 155 .58 (case 4081)

. A registration review decision is the Agency’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 n interim registration review decision before completing a registration review . Among other things, the Interim Registration Review Decision may: 1) require new ris k mitigation measures ; 2) impose interim risk mitigation measures ; 3) identify data or information required to complete the review ; and 4) include schedules for submitting the required data, conducting the new risk assessment and completing the registratio n review

. F urther information on silica gel and silicon dioxide , can be found in EPA’s public docket (EPA

- HQ

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- 1140 ) at www.regulations.gov

.

FIFRA, 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 th at they will not cause unreasonable risks to human health or to the environment when used as directed on product labeling. In 2006, the Agency implemented the registration review program pursuant to FIFRA section 3(g) and will review each registered pesti cide every 15 years to determine whether it continues to meet the FIFRA standard for registration. 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 re gistered 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 r e

- evaluates pesticides to make sure that as these changes occur, products in the marketplace can continue to be used safely. Informatio n on this program is provided at www.epa.gov/oppsrrd1/registration _review/

.

Silica gel and silicon dioxide were first registered as pesticides in 1956 and 1960

, respectively. The silicates are registered for use as insecticides to control non soil

- dwelling terrestrial invertebrates through desiccation. They are formulated as dust or wettable powders (and sometimes combined with pyrethrins and piperonyl butoxide (PBO)) and have both indoor and outdoor registered 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 40 CFR §155.50, the EPA initiated registration review for silica gel and

silicon dioxide in March 2008, when EPA open ed the silica gel and silicon dioxide re gistration review public docket ( docket number EPA

- HQ

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- 1140 , accessible at www.regulations.gov .) The following timeline highlights significant events that have occurred during the registration review of s ilica gel and silicon dioxide and can be found in the public docket ( EPA

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.Docket Number EPA

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3 • March 26, 2008

– The EPA published the Silica and Silicates Summary Document

, dated March 14, 2008 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 Silicon Dioxide and Silica Gel, dated November 16, 200 7

and the HED Registration Review Scoping Document

, dated November 16, 2007

.

• August 5, 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 silicates registration review.

• December 10, 200 9

– The EPA issued the Generic Data Call

- In Notice (GDCI

- 072602

- 847) for silica ge l and silicon dioxide . Data required by the EPA included:

o GLN 830.7050: UV/Visible absorption

o GLN 850.2100: Avian acute oral toxicity test

• March 7, 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

, d uring which time, no comments were received

.

• June 30 , 2015

– The EPA published the Silica Gel and S ilicon Dioxide Proposed Interim Registration Review Decision

, dated June 24, 2015 , for a 60

- day public comment period

, during which time, no comments were received.

• December 2015

- The Agency is now publishing the Silica Gel and Silicon Dioxide

Interim Registration Review Decision accessible on www.regulations.gov under docket

number EPA

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.



### II. Use and Usage

Silica gel and silicon dioxide are both derived from diatomaceous earth (DE) deposits

whi ch are commonly found in most soils. Silicon dioxide is diatomaceous earth, formed from a naturally

- occurring material c omposed 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 assessment.Docket Number EPA

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4 

### I I I. 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

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- 0005

, which can be accessed at http://www.regulations.gov/

.

Hazard Ch aracterization 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 silicon dioxide from direct or indirect application 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 silicon dioxide and silica gel as Generally Recognized as Safe (GRAS)

when used as food additives (21 CFR 182.90 and 182.1711 , respectively ). In addition, silicon dioxide has been exempted from the requirement of a tolerance when applied to : growing crops

, raw agricultural commodities after harvest

, and animals (40 CFR 180.1017 (a) a nd (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 d ietary (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 post

application residential exposures to occur. However based on the low toxicity of the silica gel and silicon dioxide, the EPA has determined that residential exposures to these compounds

would not be of conce rn, 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 has concluded that an occupational asse ssment is not needed.

Aggregate Exposure and Risks

Due to the EPA’s determination not to conduct either a dietary (food + drinking water) or residential risk assessment for the silica silicates, an aggregate risk assessment was not needed.Docket Number EPA

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5 Food Toleran ces

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 180.1001 (c) and (d), to growing crops, raw agricultural commodities after harve st 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, t he Agency’s Incident Data System (IDS) has approximately 280 reported inciden ts associated with silica gel and silic on dioxide (between January 1, 2010 and June 2, 2015 )

. Of the reports identified in IDS data base, 11 cases involved either silica gel or silicon dioxide (10 of moderate severity, and 1 of major severity ). The one

m ajor 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 throughout).

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 th e reports identified in the SENSOR database, 9 cases involved a single active ingredient, either silica gel or silicon dioxide (a ll c ases

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

work event whe re 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, 2 013), available in the public docket EPA

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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 broadcast applied, but more often applied as a spot treatment. Therefore, movement of silica gel and silicon dioxide away from the

treatment site via wind or rain is e xpected to be limited. Further, USGS (1984) reports that the silica silicates 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 aquaticDocket Number EPA

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6 organisms is not considered to be a risk since the mode of action of the silica silicates 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).

Ecological Risk Conclusions

1. Terrestrial Species

Based upon the low toxicity of the silica silicates, 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 regi stration review.

Based on available data, t errestrial vertebrates (including birds) 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, terr estrial 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 affecte d by silica gel and silicon dioxide due to its insecticidal properties ( i.e.

, to cut
and desiccate )

.

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 tha t these compounds will adversely affect aquatic organisms (fish or invertebrates)

.

3. Plants

Because terrestrial plants are likely to be routinel y exposed to silica, as wind bo rne 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 registrati on review interim decision for silica gel and silicon dioxide (as d iatomaceous earth) (DE) contains a completed Endangered Species Act (ESA) analysis, including effects determinations for endangered and threatened (listed) species and their designated crit ical habitat, and incorporates concurrence from the U.S. Fish and Wildlife Service (FWS) on EPA’s “Not Likely to Adversely Affect (NLAA) ” determination, i n 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 speciesDocket Number EPA

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7 for which an NLAA finding was determined. T he EPA reached this conclusion based upon the following rationale:

1. 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, 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, present 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 te rrestrial 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 a lternatives 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 i nvertebrates.

On February 10, 2014, pursuant to section 7 of the ESA, EPA requested informal consultation with the FWS and concurrence that silicon dioxide and silica gel is NLAA 57

identified listed terrestrial invertebrates.

On April 2, 2014, the 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. In an email that preceded the April 2, 2014 letter, the FWS noted that one species,

the Ash Mea dows 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 ( email

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

Sub sequent 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 ( e.g., pastures, vineyards) for two listed species of butterfly, namely the Fender’s b lue butterfly ( Icaricia icarioides fenderi ) and the Taylor’s c heckerspot 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 from exposure to DE use in pastures and /or 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 silica gel and silicon dio xide for a new use (via a section 18 or 24c label), and similar guidance is available through other e xtension s ervices. EPA also provided additional data showing low toxicity of silica gel and silicon dioxide to bees (as a surrogate for butterflies) at ra tes exceeding current application levels. Based on this additional information provided by EPA, the FWSDocket Number EPA

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8 reaffirmed their concurrence with EPA’s NLAA determination for the Fender’s Blue and Taylor’s checkerspot butterflies (see Appendix for letter from C ra ig Aubrey of U.S. FWS to

A nita Pease of U.S. EPA dated March 9, 2015 )

.

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 da ta or
information are obtained that would otherwise inform this determination.

Ecological Incidents

As of May 16, 2012, EPA searched its ecological incident databases, including the Ecological Incident Information System (EIIS), the Avian Incident Monitor ing System (AIMS), and the Aggregate Incident Reports database. In the EIIS, 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 mi suse” 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 Aggre gate Incident Reports database.

C. Endocrine Disruptor Screening Program

As required by FIFRA and the Federal Food, Drug, and Cosmetic Act (FFDCA), EPA reviews numerous studies to assess potential adverse outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and chronic toxicity, including a ssessments 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 ef fects in different taxonomic groups. As part of its most recent registration decision for the silicates, 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 a ctive 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 th e 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 availableDocket Number EPA

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9 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 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 published on Ju ne 14, 2013 1 and includes some pesticides scheduled for registration review and chemicals found in water. Neither silicon dioxide nor silica gel are on either list 1 or list 2. For further information on the status of the EDSP, the policies and procedure s, the lists of chemicals, future lists, the test guidelines and the Tier 1 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 sil icates . Before completing this registration review, the EPA will make an EDSP FFDCA section 408(p) determination.



### IV. Interim Registration Review Decision

EPA has completed qualitative human health and ecological risk assessment s , including

an endangered species assessment

, for silica gel and silica dioxide. The EPA has also updated its silica gel and silicon dioxide database by receiving the following data required under the registration review GDCI (GDCI

- 072602

- 847).

• GLN 830.7050: UV/Visible absorption

• GLN 850.2100: Avian 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 adverse ecological effects from the use of pesticide products that contain silica gel and

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

- dwelling insects). The EPA believ es that potential effects to these species would be limited in time, since the effects of silica gel and silicon dioxide only la st until a

rainfall event occur s (when the rain would cause the compounds to clump and lose its mode of action). In addition, E PA 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 is suing this i nterim

r egistration review decision

. Pending the outcome of the EDSP analysis for silica gel and silicon dioxide, the EPA has made the following interim d ecision :

1 See docket number EPA

- HQ

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- 0477 at http://www.regulations.gov/ for the final second list of

chemicals.

2 http://www.epa.gov/endo/Docket Number EPA

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10 • Because of low toxicity, the EPA conducted qualitative human health and ecologi cal analyses and determined that no risks of concern are likely to result from the current registrations of either silicon dioxide or silic a gel; and no data or label changes are needed for either silicon dioxide or silica gel.

• EPA has made a “No Effect” d etermination under the 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 these/all 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.



### V. Next Steps and Timeline

Interim Registration Review Decision

A Federal Register Notice will announce the availability of this i nterim r egistration

r eview d ecision for silica gel and silicon dioxide. A final decision on the silica gel and silicon

dioxide registration review case will occur after an EDSP FFDCA section 408(p) determinat ion.



### VI. Appendix: Informal Endangered Species Consultation

A. Review of Informal Consultation on the Proposed Registration of Silicon Dioxide and Silica Gel for Two Butterfly Sp e c i es (letter from FWS dated March 9, 2015)

B. Informal Consultation on the Propo sed Registration of Silicon Dioxide and Silica Gel (letter from FWS dated April 2, 2014)