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Discussion Paper: Dossier Requirements for New Insecticide Active Ingredients

for Vector Control (Physical Chemistry and Toxicology)

Prepared by: Vicki L. Dellarco (VL Dellarco Independent Consultant), Patrick Rose (JSC International Limited), Werner Bomann (toxconsult), Steven Bradbury (SP Brad-bury and Associates), Sian Ellis (JSC International Limited)1

Objective Day 1 of the WHO PQT VCPAG Workshop on Dossier Requirements and Proposed Inspection

Protocol will focus on dossier requirements for new active ingredients developed for use in vec-tor control. In the case of a new active ingredient (AI), a human health risk assessment of the pesticide AI is needed before a product which contains the specific AI can be submitted to PQT VCPAG for review. The environmental impact must also be assessed as a result of the pesti-cide product’s use. Understanding the fate and transport characteristics of an active ingredient in the environment as a function of its applied formulation and the ecotoxicological effects through the submission of toxicity studies, allows an environmental risk assessment to be con-ducted. WHO will present on current approaches to risk assessment development as part of the Joint Meeting on Pesticide Residues (JMPR) agreement between WHO and Food and Agriculture Organization (FAO), and on product specific risk assessments based on toxicological endpoints of the AI.

This proposal will be presented at the workshop to stimulate discussion regarding test-ing and assessment approaches and how those approaches may differ in the case of AIs developed for vector control purposes. It was developed to help clarify the amount and types of safety data to collect for vector control insecticides, and to elicit feedback on improving the efficiency and accuracy of the current toxicology testing paradigm in protecting public health and the environment. Increasing effectiveness and efficiency

1The authors received support from IVCC but have sole responsibility for the writing and con-

tents of this paper. This paper represents the professional opinions of the authors and not nec-essarily those of the IVCC.

A series of tables on information requirements (physical-chemistry, health effects, and ecological effects) are provided for assessing insecticides used in vector control. Alt-hough the term “requirement” is used in the document, it is not intended to denote a regulatory or statutory requirement. Tables are not to be viewed as a rigid check list. Alternative approaches are noted in this proposal that could satisfy traditional data re-quirements. Authorities should be consulted on their data requirements and on the use of alternative information to meet regulatory data requirements.

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will reduce the time to deliver important public health protection and access to benefits, and promote the responsible use of resources and laboratory animals. This paper will focus on new AIs, but the concepts and strategy are broadly applicable to other chemical situations. In developing the tables contained in this paper, guidelines (e.g., WHO, 2013) and statutory data requirements (e.g., US Code of Federal Regula-tions, Part 158) for the registration of pesticides were considered.

Background A robust safety database is essential to an assessment of the potential risks associated with pesticide exposures. However, robust does not imply quantity over quality and rel-evance. Over the last decade, there have been a number of global initiatives to move away from a chemical and pesticide testing paradigm that relies heavily on data from a traditional battery of animal studies to a hypothesis-based approach that enables focus on the information most relevant to assessing the exposure scenarios of interest (e.g., Embry et al., 2014 and http://www.risk21.org/?page_id=67; also see https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/strategic-vision-adopting-

21st-century-science). Although there is a general expectation of more extensive information to assess the ac-tive ingredients of pesticides, there have been recommendations on improving the effi-ciency of the current testing paradigm. Several years ago, there was an international effort under the auspice of ILSI’s Health and Environmental Science (HESI) Institute to re-think the testing approach for agricultural chemicals. HESI’s Agricultural Chemical Safety Assessment project identified substantial modifications of the testing require-ments to address potential omissions and redundancies in current pesticide testing. They proposed generating chemical-specific pharmacokinetic data earlier in the devel-opment pipeline to inform study design and data interpretation (Carmichael et al., 2006; Barton et al., 2006; Cooper et al., 2006; Doe et al., 2006). More recently, the Council of Canadian Academies (CCA) reviewed the status of pesticide testing and re-emphasized the importance of integrative testing strategies as a pragmatic way to move away from a one size fits all - prescribed battery of tests, and to move toxicology from what happens to how it happens (CCA, 2012). An important risk management goal for vector control insecticides is to ensure efficiency in the data collection process while providing a relevant and robust safety database so that hazards and risks can be weighed against the benefits of these products. Signifi-cant advances have been made in knowledge of pesticide toxicology and mechanisms, a number of recommendations for improving testing/assessment paradigms have been put forward, and new methods continue to emerge. It is considered timely to reflect on and consider these proposals and advances in the toxicology requirements for vector control insecticides.

Overall Approach

(Problem Formulation Defining Exposure and Creating Risk Hypotheses)

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To focus data collection, the approach begins with problem formulation and defining the exposure scenarios associated with vector control insecticide uses. What is already known about the insecticide’s toxicological profile (e.g., early testing/screening results, mode of action understanding of chemical/class, data on similar compounds) is fully utilized to formulate and evaluate risk-based hypotheses on the potential adverse effects. The process is tiered where initial risk modeling is performed to identify uncertainties, determine the need to further collect data, and refine the risk assessment.

Physical Chemistry Requirements (Table 1) Table 1 depicts the product chemistry data requirements. Product chemistry provides basic information needed for all pesticides (including vector control insecticides) regard-less of the use. These data play an important role in evaluating potential hazard, expo-sure, and risk in a number of ways. Test substance identity ensures that the Technical Grade Active Ingredient (TGAI) test-ed in the toxicology studies is essentially the same as production material (i.e., it is rep-resentative of the AI and impurities content associated with the manufacturing process used to produce the TGAI, thus, the same specification). The identification/quantification of impurities of toxicological concern associated with the TGAI by the manufacturing process are particularly important, as the impurities may be more toxic than the AI and/or exert different toxic effects. The relevance, extent, and significance of human and environmental exposure for each of the vector uses can be assessed based on the physical-chemical properties of the substance (e.g., likely route(s) of human exposure or behavior of a pesticide in the envi-ronment with respect to its mobility and accumulation). Data on physical-chemical prop-erties can be used in a weight-of-evidence approach to justify a waiver for test guideline studies. Human Exposure Scenarios Associated with Vector Control Insecticides (Table 2) Characterization of the exposure scenarios begins with a consideration of the use direc-tions on the product label. The insecticide uses, use rates, and application intervals will help define the conditions of human and environmental exposure with regard to the population exposed, routes and durations, frequency, and magnitude of exposure. Ta-ble 2 depicts the human exposure scenarios by population groups, routes and durations of exposure associated with vector control insecticide uses. These scenarios are de-rived from and described more fully in the WHOPES risk model documents (WHO 2011a, b and c, and 2012). In general, the inhalation exposure pathway is considered negligible compared to the dermal and incidental oral (hand/object to mouth or ingestion of contaminated water/soil) exposure pathways, particularly for the resident scenarios. However, the importance of assessing inhalation exposure will depend on the insecti-cide’s vapor pressure and degree of potential route-specific toxicity. In addition to the routes of exposure, the durations of exposure are provided in Table 2. Some scenarios

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involve long-term or chronic exposure (e.g., sleeping every night under treated bed nets, long lasting indoor residual spray (IRS), larviciding). And some scenarios involve acute exposure (e.g., washing nets). The understanding of the temporal relationships and routes of exposure are important to appropriately matching the toxicity and expo-sure data for assessing risk. Mismatches of the exposure routes and durations with the toxicity data should be avoided to the extent possible to minimize uncertainty in charac-terizing risks.

Strategy for Determining Health Effects Requirements (Figure 1 and Table 3) The studies listed in Table 3 should not be viewed as a checklist but rather a toolbox where some studies are considered basic information requirements that contribute to the initial evaluation of hazard regardless of the vector control exposure scenario. Other studies may be needed to further refine a life-stage issue or an assessment endpoint or toxic response presenting via a route or duration of exposure.

The overall strategy for determining the toxicology requirements is outlined in Figure 1 and begins with defining the vector control exposure scenarios (by population, route, duration/frequency) and formulating risk hypotheses for each exposure scenario. Risk hypotheses are evaluated in a tiered manner based on physical-chemical properties, knowledge of absorption, metabolism, distribution and elimination kinetics, preliminary findings from acute and repeated dose studies, and any other existing information on the chemical and its class including mode of action. The approach depicted in Figure 1 and Table 3, points out opportunities for the use of alternative approaches (e.g., read-across strategies, waiver rationales, modified study protocols) in lieu of conducting a traditional test guideline study. Any alternative ap-proach needs to be clearly explained, credible and scientifically valid. Supporting infor-mation should be submitted that is relevant to the effect of concern. Consideration should be given to how an alternative approach could be strengthened with information on structure activity relationships, mechanistic information from in vitro (e.g., stem cells, metabolism, receptor binding assays) or short term in vivo (e.g., cell proliferation, histo-pathology, micro-array analysis) studies. An important aspect of the approach is to generate data early on absorption, metabo-lism, distribution, excretion (ADME). ADME and toxicokinetic data can play a role in study design and dose selection, route-to-route extrapolations (e.g., understanding first pass effects, oral absorption) and estimating internal or systemic dose (versus adminis-tered dose). Mutagenicity is a basic information need that is not use specific. This information is im-portant for evaluating how chemicals affect the genetic material of the cell and potential modes of action for specific toxicities (e.g., carcinogenicity). Acute toxicity data are also basic information, which is needed for classifica-tion/precautionary labeling. Additionally, this information contributes to the initial hazard assessment. In some situations, acute toxicity data requirements can be satisfied by

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alternative information including read-across strategies, waiver rationales, and in vitro/ex vivo studies (USEPA, 2012 and 2016a; ECHA, 2015). Sub-chronic and prenatal toxicity studies are also basic requirements for all vector sce-narios that provide an understanding of target organs, life stage effects, and used for evaluating risk hypotheses. Along with consideration of the exposure situation, these studies are important for information about the need for more specialized testing (e.g., concerns for neurotoxicity, thyroid or endocrine toxicity, immunotoxicity, carcinogenici-ty). Short-term repeated dose study protocols could be augmented with additional end-points as indicators for the potential presence (or absence) of special toxicity effects. Toxicity testing is typically focused on the oral route of exposure, which is needed for evaluating the incidental oral exposure scenarios (Table 1). Although the oral route is not directly applicable to operators or residents that are exposed through skin contact, a lower tiered or screening level risk assessment could be based on extrapolating oral toxicity values to dermal values with default assumptions on absorption to estimate sys-temic exposure. If there is a specific exposure route of concern (e.g., dermal exposure and lack of first pass effects and higher systemic dose of the parent) or a need to refine the dermal risk assessment, two options could be considered. Firstly, dermal absorp-tion could be assessed using an in vitro rat/human study as a first tier, followed by an in vivo rat dermal absorption study if necessary, to improve the accuracy of extrapolating the oral data in assessing dermal exposure. Secondly, the dermal exposure route could also be addressed by conducting a sub-chronic dermal toxicity study, and then conduct-ing the in vitro and in vivo rat dermal penetration studies as a higher tiered approach. Inhalation is generally not a major route for most vector scenarios (particularly for the resident) compared to incidental oral and dermal exposure pathways. However, if there is significant inhalation exposure and a concern for inhalation toxicity, a 28 or 90-day inhalation rat study should be considered. As shown in Table 2, there are several vector scenarios where acute exposure need to be considered and addressed. The derivation of acute reference doses (ARfD) has been the subject of both JMPR and OECD guidance (Solecki et al., 2015a). Recent ret-rospective analyses of pesticides used in agricultural and in residential settings, indicat-ed an ARfD was necessary about 40-50 percent of the time (Holman and Gray, 2014; Solecki et al., 2015b). Since an ARfD is not always necessary and would depend on the intrinsic properties of the substance, one could use the repeated dose and prenatal studies, ADME data, as well as knowledge of mode of action (if available) to assess the likelihood of effects presenting after a single dose. An ARfD could be based on relevant acute effects in repeated dose studies (which may be a conservative first tier approach). If the risk threshold is exceeded, the exposure estimate could be refined or the endpoint could be refined by conducting an appropriate single dose study. In the case, of a neu-rotoxic insecticide, this would be an acute neurotoxicity study. For scenarios where a significant portion of lifespan is exposed in terms of frequency, magnitude or duration, reproductive and cancer studies are typically required (sleeping

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under bed nets, an operator applying a larvicide, long lasting IRS). These requirements could be addressed by an alternative approach based on a weight-of-evidence evalua-tion using read-across/structural activity relationships, relevant endpoints from short-term studies (e.g., histopathology, organ weights and clinical chemistry), ADME, mech-anism studies and the margin of exposure. Early screening tests for potential reproductive/developmental toxicity may contribute to decisions on further test requirements. An alternative approach to the traditional test guideline multi-generation study might be adapting the extended F1 reproductive study for the specific pesticide-exposure situation. Early F1 in-life indicators would be consid-ered along with any existing information to indicate the need to extend the F1 study to the 2nd generation. It should be noted that a retrospective analysis of 498 multi-generation reproductive studies found that the 2nd generation mating and offspring will very rarely provide critical information (Piersma et al., 2011). Furthermore, to determine the potential for pre-natal toxicity, a single species (rabbit) developmental toxicity study could be conducted (ECHA, 2014). The second species requirement could be satisfied with data on the rodent (rat) being addressed with the measures (e.g., pup death, pup weight alterations, and gross structural anomalies) in the extended F1 reproductive study (Cooper et al., 2006). The need for a separate rat pre-natal study would be de-termined based on the observations in the extended F1 study (as proposed by Cooper et al., 2006) and other relevant information (ECHA, 2014). The relevance of the mouse cancer bioassay has been long debated, and based on ret-rospective analyses, some have proposed that this study is no longer a scientifically jus-tifiable core data requirement for the safety assessment of pesticides (Billington et al., 2010). This assay still remains a regulatory data requirement for pesticides and is a possible data requirement for biocides in the EU (ECHA, 2014). On a case-by-case ba-sis, an alternative approach to satisfy the carcinogenicity information requirement for a non-genotoxic chemical could be addressed with a robust read-across strategy supple-mented with in vitro/in vivo mechanistic data and relevant histopathology from sub-chronic studies. Alternatively, one could conduct a rat bioassay supplemented with rel-evant data from shorter-term studies and mechanistic information. Lastly, special toxicities (immunotoxicity, neurotoxicity, endocrine toxicity) should be ad-dressed if raised by the chemical class or mode of action, existing information or early testing results. Standard test guideline repeated dose studies already incorporate a number of measures to help determine whether or not a specialized study is needed. These measures include organ weights and histopathology of the relevant or-gans/tissues, clinical signs (neurotoxicity), and changes in serum globulin levels and haematology (immunotoxicity). Additional indicators of endocrine toxicity in the prenatal studies, and in an early reproductive screening study or a guideline reproduction study would include observations of effects on fertility/fecundity, reproductive tract malfor-mations, altered sex ratio, altered viability of the embryo/fetus and reduced litter size. Short-term repeated dose studies could be augmented with additional endpoints (e.g., circulating hormones, behavioral assessments). Although immunotoxicity and neurotox-

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icity studies are required by certain authorities, these requirements could be addressed by a waiver rationale using a weight-of-evidence approach (e.g., USEPA, 2013).

Strategy for Determining Ecological Effects Requirements (Table 4) There are a number of potential environmental exposure scenarios associated with vec-tor control insecticides including exposure via treated bed nets, exposure via indoor re-sidual spraying, and exposure via larviciding spray drift and via outdoor space spraying. In evaluating these scenarios, the physical-chemical properties of the insecticide play a critical role in determining the relevance and significance of environmental exposures for each of the vector control use. These properties can be used to justify a waiver for a range of studies. • DT50 : if the substance has a low DT50 and is shown to degrade rapidly chronic expo-

sure is unlikely to be relevant and as such chronic studies could be waived. The fre-quency of exposure however would need to be considered. If the frequency was likely to be daily for example and is such more frequent than the DT50 time-frame then chronic exposure would need to be considered as a quasi-continuous exposure could not be ruled out.

• Kow: The octanol:water partition coefficient (Kow) can be used to initially assess the potential for bioaccumulation and secondary poisoning of fish, birds and mammals. In accordance with the EFSA Guidance of Risk assessment for Birds and Mammals (2009) substances with a log Kow of <3 are unlikely to be bioaccumulative and so this exposure pathway would not be applicable.

• Koc: The soil-organic carbon:water partition coefficient (Koc) can be used to initially assess the potential for the substance to partition to sediment (and soil) can be ap-plied to determine if exposure to sediment dwelling/soil organisms is relevant. If the Koc is low then exposure is unlikely and sediment studies could be waived.

These scenarios are further discussed below. Table 4 provides the information re-quirements for lower and higher tiered assessments. These requirements could be ad-dressed by an alternative approach based on a weight-of-evidence evaluation using read-across/structural activity relationships. Figure 2 provides the overall testing strate-gy and decision logic. Similar to health effects, determining the data requirements for ecological effects begins with defining the potential exposure scenarios and formulating risk hypotheses based on physical-chemical properties of the substance. 1. Exposure via Treated Bed Nets: A. Secondary poisoning to birds via ingestion of dead insects (swept outside) The exposure to birds from ingestion of contaminated insects that were in contact with treated nets is likely to be minimal. Exposure via this route can be assessed based on effect concentrations (NOAEC or LC50) available from efficacy data or acute contact studies with honey bees (if available), which can be used to calculate the potential ex-posure from individual dead insects. This can then be combined with available data on

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the diet of insectivorous birds (e.g., EFSA Guidance on the Risk Assessment for Birds and Mammals 2009) to calculate a potential daily dose (assuming that 100 % of the diet was from contaminated insects to provide a conservative dose). Avian studies could therefore be waived based on low predicted exposure. Should a high potential exposure be predicted based on exposure calculations, acute oral studies would be triggered or alternatively, as a screening step, mammalian acute oral toxicity data used as surrogate in the interests of minimizing vertebrate testing (assuming for other pesticides in the class birds are known to not be more sensitive than mammals). A similar assessment can be made for chronic exposure but the rate of degradation of the substance (DT50) should also be taken into account to determine if a prolonged exposure required for chronic toxicity is relevant. B. Exposure to water/sediment via washing nets To determine the potential for exposure from washing treated nets, the maximum amount the substance to ‘wash out’ from the nets should be determined and the fre-quency of washing also considered when determining the potential exposure via this pathway. It is likely there will be a high level of dilution from the water bodies which would also reduce the concentration of the substance and exposure to aquatic organ-isms. As washing nets is unlikely to be a frequent occurrence a short DT50 (less than a few days) indicating rapid degradation would justify chronic studies to be waived. C. Exposure to water/sediment via disposal of the treatment solution If nets are intended to be re-treated with solution containing the active substance, expo-sure to surface water could occur from disposal of the un-used treatment solution. The relevance and potential for exposure via this pathway can be assessed for each prod-uct. Registrants should aim to ensure there is minimal unused product to minimize the potential exposure to both the environment and humans. A calculation of the amount of solution used and how often re-treatment is likely to occur can be used to estimate the release of the substance into surface water. The physical chemical properties listed above can be assessed to determine relevance of sediment exposure, chronic exposure and bioaccumulation. 2. Exposure via larviciding spray drift & via outdoor space spraying: Application to water bodies for larviciding and outdoor space spraying will result in ex-posure to aquatic organisms when applied directly to water or via spray drift/run-off. The partitioning of the substance, the persistence and frequency of application will deter-mine if chronic exposure, sediment exposure and bioaccumulation are relevant. Where exposure to surface water is expected from the application, acute tests on aquatic or-ganisms representing the three trophic levels (fish, aquatic invertebrates and algae) should be provided. If sediment exposure or prolonged exposure due to persistence are predicted, then sediment organisms (Chironomus riparius) study should be provided an-ticipated, chronic studies may be required if acceptable risk cannot be shown at the acute level with additional assessment factor.

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The potential for soil exposure will need to be assessed for each specific use. For appli-cations intended around dwellings as example it may not be relevant to assess the risk to soil organisms as the surrounding could not necessarily be considered agricultural or ‘natural’. Soil exposure to relevant soil ecosystems, however, may result from spray drift from the larviciding application. An equilibrium partition coefficient calculation can be used to assess the risk to soil organisms based on the aquatic organism endpoints as a screening step. If a likely risk is predicted soil organisms studies may be required. Acute earthworm studies would be relevant for low persistence substances (with a low fre-quency of application) but for more persistent substances (or with high frequency of ap-plication) chronic studies would be relevant. An assessment of the effects on soil mico-organism (carbon or nitrogen transformation) would also be relevant if soil exposure is likely. 3. Exposure via indoor residual spraying: The potential environmental exposure from indoor residual spraying is likely to be mini-mal. The guidance notes that ‘insecticide applied internally to the walls of the house and externally to the house will contaminate house dust, floor materials and soil adjacent to the house at a low level. Sweeping the house will transfer this contaminated material to the surrounding soil’. This potentially could lead to exposure to soil organisms and a marginal exposure to birds feeding on the ground. The frequency of use and persis-tence of the substance should be considered to determine if this is a significant path-way. For birds the potential dose could be calculated based on the available data as described for exposure via nets.

Conclusion The current testing paradigm for pesticides is time-consuming, costly, and heavily relies on the use of laboratory animal studies. A strategy is offered to determine the toxicolo-gy requirements for new insecticides used for vector control. This strategy is intended to increase the efficiency (cost and time) and the accuracy of the information in assessing risk posed by vector control insecticides. An overall goal of the approach is to produce data of value for the evaluation of risk by taking into account the exposure use patterns (route, dose, frequency and duration) and the toxicological properties of the insecticide. The approach is hypothesis-based and tiered to determine what studies should be done (and in what order) for risk assessment; i.e., applying the best available science to de-velop intelligent testing strategies.

In moving forward, it will be important to achieve consensus with an expanded group of

experts, and to develop case examples illustrating use of alternative approaches to sat-

isfy data requirements.

A series of questions are posed below to stimulate dialogue on the proposal:]

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1. We have attempted to establish a logical, relevant and scientifically credible basis for risk assessment and characterization of vector control insecticides. Please comment on the approach.

• Does it provide adequate information to assess the relevant exposure situations?

• Are there ways to further improve the approach?

• Are there concerns with the approach, e.g., regulatory acceptability? What is missing?

2. The approach outlines a flow of studies that are conducted in a certain order, where early test protocols could be augmented with endpoints as indicators for more focused and specialized testing as needed. Is further guidance or clarification needed on this approach?

3. What are the major issues that need to be addressed to make alternative approaches (e.g., read-across strategies) acceptable to authorities as satisfying data used to derive references doses for insecticide active ingredients?

4. For companies that may choose to develop a product for both vector control and ag-ricultural uses, is the proposed strategy still useful? Or would the approach need to be modified? If so, how?

References

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A.H. Piersma, E. Rorij, M.E.W. Beekhuijzen, R. Cooper, D.J. Dix, B. Heinrich-Hirsch, M.T. Martin, E. Mendez, A. Muller, M. Paparella, D. Ramsingh, E. Reaves, P. Ridgway, E. Schenk, L. Stachiw, B. Ulbrich, B.C. Hakkert (2011). Combined retrospective analy-sis of 498 rat multi-generation reproductive toxicity studies: On the impact of parameters related to F1 mating and F2 offspring. Reproductive Toxicology 31: 392-401. Solecki R, Davies L, Dellarco V, Dewhurst I, van Raaij M, Tritscher A. (2005). Guidance on set-ting of acute reference dose (ARfD) for pesticides. Food Chem Toxicol 43:1569–1593.

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Table 1. Product Chemistry Information.*

Product Identity and Composition

Study Guideline Test Material

Product Identity & Composi-tion

OPPTS 830.1550 WHO/FAO 2002. Pesti-cide specifications.

MP, TGAI, EUP

Description of materials used to produce the product

OPPTS 830.1600 MP, TGAI, EUP

Description of production pro-cess

OPPTS 830.1620 MP, TGAI, EUP

Description of formulation process

OPPTS 830.1650 MP, TGAI, EUP

Discussion of formation of im-purities

OPPTS 830.1670 MP, TGAI, EUP

Results of preliminary analy-sis of product samples

OPPTS 830.1700 MP, TGAI, EUP

Explanation of how the certi-fied limits were determined

OPPTS 830.1750 MP, TGAI, EUP

Description of the enforce-ment analytical method

OPPTS 830.1800 MP, TGAI, EUP

Submittal of samples OPPTS 830.1900 TGAI (MP & EUP case-by-case)

Physical Chemical Properties

Color OPPTS 830.6302 TGAI

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Physical State OPPTS 830.6303 TGAI, EUP

Odor OPPTS 830.6304 TGAI

Stability to metals, metal ions, sunlight and elevated temper-ature

OPPTS 830.6313 TGAI Stability to metal/metal ions need-ed only if contact during storage or use likely.

Oxidation/reduction (chemical incompatibility)

OPPTS 830.6314 MP, EUP

Flammability OPPTS 830.6315 MP, EUP Useful for label warnings

Explodability OPPTS 830.6316 MP, EUP Useful for label warnings

Storage stability OPPTS 830.6317 MP, EUP

Miscibility OPPTS 830.6319 MP, EUP

Corrosion characteristics OPPTS 830.6320 MP, EUP Useful for label warnings

Dielectric breakdown voltage OPPTS 830.6321 EUP Only for liquids used near electrical equipment or outlets. This may apply to larviciding and indoor and outdoor spraying.

pH OPPTS 830.7000 OECD 122

MP, TGAI, EUP

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Viscosity OPPTS 830.7100 OECD 114

MP, EUP

UV/visible light absorption OPPTS 830.7050 OECD 101

TGAI

If the test substance contains a UV chromophore.

Helpful in determining the potential of chemical to degrade when ex-posed to sunlight in air, water, or soil.

(If substance absorbs light within range of natural sunlight, has the potential to generate a reactive species following absorption of UV visible light, and would distribute sufficiently to light expose tissues, the potential for phototoxicity should be considered.)

Melting Point/melting range OPPTS 830.7200 OECD 102

TGAI If the test substance is a solid at room temperature.

Boiling Point/boiling range OPPTS 830.7220 OECD 103

TGAI If the test substance is a liquid at room temperature.

Density OPPTS 830.7300 OECD 109

MP, TGAI, EUP

Dissociation constants in wa-ter

OPPTS 830.7370 OECD 112

TGAI (or PAI)

Partition coefficient (n-octanol/water)

OPPTS 830.7550, 830.7560, 830.7570 OECD 107 and OECD 117

TGAI (or PAI)

Helpful in determining when fish bioaccumulation studies are need-ed.

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Water solubility OPPTS 830.7840, 830.7860 OECD 105

TGAI (or PAI)

Vapor pressure OPPTS 830.7950 OECD 104

TGAI (or PAI)

* Product chemistry data are not use-specific and required for all pesticides. Many of these parameters are needed to support exposure models and help focus on likely ex-posure pathways.

Table 2. Vector Control Human Exposure Scenarios based on WHO models.

Exposure Scenario Population Route of Exposure Duration of Exposure

Sleeping under Long-Lasting Insecticidal Nets (LLIN)

All ages (in-fants, children, adults)

Dermal, Incidental oral (children - hand to mouth transfer and sucking nets; infants - breast milk) (Inhalation route likely to be negligible, but dependent on insecti-cide’s vapor pressure and degree of potential route-specific toxicity)

Long-term

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Table 2. Vector Control Human Exposure Scenarios based on WHO models.

Exposure Scenario Population Route of Exposure Duration of Exposure

“Do-it-yourself” net treatment (dipping) or Washing of Bed Nets

Adults, children Dermal, Incidental oral (hand to mouth trans-fer; infants - breast milk)

Acute (relevant duration) Long-term (TWA) Nets are washed fairly infre-quently (20 washes over 3 years). WHO model uses a TWA exposure calculated as sin-gle day exposure x (20/3)/365 days and compar-ison with the ADI (chronic RfD). Dipping of nets is assumed to be 5 nets, 4 times per year. The exposure is added to that from sleeping under the net to give the total acute or TWA exposure

Occupational indoor residual spraying (IRS)

Adults Dermal, Inhalation Acute Long-term (TWA) WHO approach (72 days per 365 days) to compare with the ADI (chronic RfD,) and a maximal daily dose for acute exposure.

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Table 2. Vector Control Human Exposure Scenarios based on WHO models.

Exposure Scenario Population Route of Exposure Duration of Exposure

Post-application following IRS (resident and operator living in sprayed house)

All ages (infants, children, adults)

Dermal, Incidental oral (children-hand to mouth transfer; chil-dren and adults- inges-tion of contaminated foodstuff; infants-breast milk) (Inhalation route likely to be negligible due to aerosol settling and deposition, but de-pendent on insecti-cide’s vapor pressure and degree of potential route-specific toxicity)

Acute The acute estimate is from the initial concentration on the walls. Long-term (TWA) for long lasting IRS. WHO model assumes 6 months interval for all IRS. The exposure over 6 months is estimated assuming a T/1/2 of 60 days for the concentra-tion remaining on the walls. Could consider shorter inter-vals for IRS where relevant (e.g. 3 months).

Occupational larvicide outdoor spraying

Adults Dermal, Inhalation (Inhalation likely to be negligible for liquid sprays due to large droplet size and downward spraying)

Acute Long-term (TWA) WHO model assumes spray-ing 6 days per week for 6 months per year. TWA over 365 days.

Post-application following larviciding (resident and operator living in sprayed area)

All ages (infants, children, adults)

Dermal, Incidental oral (children and adults; ingestion of treat-ed/contaminated wa-ters; infants-breast milk) (Consideration of use of larvicides in potable water*)

Acute and long-term (TWA) WHO model assumes larvi-ciding at 7-day intervals dur-ing a 6-month season.

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Table 2. Vector Control Human Exposure Scenarios based on WHO models.

Exposure Scenario Population Route of Exposure Duration of Exposure

Occupational indoor and outdoor space spraying

Adults Dermal, Inhalation Acute Long-term (TWA) WHO model assumes spray-ing 6 days per week for 6 months per year. TWA over 365 days.

Post-application following space spraying (resident and operator living in sprayed house or area)

All ages (infants, children, adults)

Indoor Similar to IRS Outdoor Inhalation added to indoor dermal and oral (Ingestion of contami-nated foodstuffs grown in an area contaminated from space spraying)

Acute and long-term (TWA) WHO model assumes 15 exposure days per year. TWA over 365 days.

TWA = time weighted average over 365 days; * According to WHO ‘Generic risk assessment model for insecticides used for larviciding’ (WHO, 2011c).

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Table 3. Effects information for assessing human health hazards and risks from insecticides used for vector control.

Acute Toxicity (TGAI, EUP)

Study Guideline Comments

Acute oral toxicity (rat)

OPPTS 870.1100 OECD 423, 425

Alternative: Opportunities for read-across/bridging or waiver rationale.

Acute dermal toxici-ty (rat)

OPPTS 870.1200 OECD 402

Alternative: Opportunities for read across/bridging or waiver rationale. Note: USEPA will accept acute oral classi-fication on a case-by-case basis (USEPA, 2016b).

Acute inhalation tox-icity (rat)

OPPTS 870.1300 OECD 403, 436

Alternative: Opportunities for read-across/bridging or waiver

Primary eye irritation (rat or rabbit)

OPPTS 870.2400 OECD 405, 437, 438

Alternative: Bovine corneal opacity test, Isolated chicken eye, Cytosensor micro-physiometer modified, and Epi-Ocular as-say.

Primary dermal irri-tation (rat)

OPPTS 870.2500 OECD 404, 439

Alternative: Reconstructed Human Epider-mis models (various)

Dermal sensitization (guinea pig)

OPPTS 870.2600 OECD 406, 429 442A, 442B, 442C, 442D

Alternative: In silico and in vitro. Mouse LLNA or reduced LLNA

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Mutagenicity Testing (TGAI)

Bacterial reverse mutation

OPPTS 870.5100 OECD 471

In vitro mammalian cell mutation assay

OPPTS 870.5300 OECD 490

In vitro mammalian cell chromosomal aberration assay

OECD 473, 487 In vitro micronucleus test (487) and bacterial mutagenicity test without a mammalian mutation test may be sufficient

In vivo cytogenetics OPPTS 870.5385 OECD 474, 475

USEPA will considered protocol integrated into the standard 90 day oral study. see https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/advances-genetic-toxicology-and-integration-vivo

In vivo gene muta-tion (somatic cells) or germ cell assays

OECD 483, 488, 489

If required: Comet assay or Transgenic Rodent Assay (488)

Subchronic Testing (TGAI)

Oral 14, 28 (range finding)/90-day (rat)

OPPTS 870.3100, OECD 407,408

Provides basic information for characterizing chemical’s toxicity profile and for deriving reference doses, if there are no specific concerns for other routes of exposure. Could be augmented with additional endpoints as indicators to determine need for testing on specific effects/organs (neurotoxicity, thyroid toxicity, immunotoxicity, carcinogenicity). Recovery periods could be added to better determine risks from intermittent exposures (e.g., IRS, larviciding, net washing)

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Oral 14, 28 (range-finding)/90-day (dog)

OPPTS 870.3150, OECD 409

Provides basic information in a second species for characterizing chemical’s toxicity profile.

Dermal 28/90-day (rat)

OPPTS 870.3200, OECD 410, 411

Should be considered if repeated dermal exposure occurs, and if there is high acute dermal toxicity, significant dermal absorption, and/or pharmacokinetic differences between the oral and dermal routes of exposure (e.g., high systemic dose of the parent compound or site specific metabolism).

The inhalation pathway is generally negligible for various vector control scenarios (e.g., bed net scenarios, post-application following IRS and Larvicide spraying), compared with dermal and incidental oral exposures. But if there is significant repeated inhalation exposure to a gas, vapor, or aerosol, a 28-or 90-day inhalation rat toxicity study should be considered, particularly for characterizing port-of-entry effects.

Reproductive/developmental Testing (TGAI)

Prenatal develop-mental toxicity oral (rat and rabbit)

OPPTS 870.3700, OECD 414

Provides basic information for characteriz-ing the potential, nature and severity of ef-fects during development. Alternative: Conduct a rabbit prenatal tox-icity study and evaluate effects on prenatal development in rats from observations on pups in the Extended F1 Reproductive Study (OECD 443) to determine the need for a separate rat prenatal developmental toxicity study (Cooper et al., 2006).

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Reproductive/fertility oral (rat)

OPPTS 870.3800, OECD 416, 443

Alternative: Conduct Extended F1 Reproductive Study (OECD 443) using animal cohorts and endpoints (e.g., endocrine, neurotoxicity, immunotoxicity) as appropriate for the chemical’s intrinsic properties. Note: “Decisions to assess 2nd generation or to omit the neurotoxicity cohort and/or developmental immunotoxicity cohort should reflect existing knowledge of the chemical being evaluated.” This study may not be needed if there is no significant systemic dose or long-term exposure, and no concern for endocrine or reproductive toxicity based on the weight-of-evidence (e.g., sub-chronic studies, read across/SAR, in vitro receptor binding and gender activation assays, in vivo mechanistic endpoints) which may include an early reproductive screening study.

Chronic Testing (TGAI)

Chronic oral (rat) OPPTS 870.4100 OECD 453

If >6 month human exposure or over signif-icant part of lifespan.

Cancer oral (mouse) OPPTS 870.4200 OECD 451

If >6 month human exposure or over signif-icant part of lifespan. Alternative: Conduct rat bioassay only and supplemented with special studies (e.g., in vitro receptor binding, in vivo microarray analysis, augmented sub-chronic rat study) This study may not be needed if there is no concern for carcinogenicity based on a weight-of-evidence approach (e.g., muta-gencity testing, sub-chronic studies, read across/SAR, in vitro receptor binding as-says, in vivo microarray analysis).

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Special Testing (TGAI)

ADME oral (rat) OPPTS 870.7485 OECD 417

ADME studies should be conducted prior to the conduct of the repeated dose toxicity studies. Provides basic information on estimated percent of administered dose absorbed, PK parameters, excretory metabolites, rate of excretion and tissue residue levels. ADME data may be required in other spe-cies if there are concerns for species dif-ferences in metabolism. This can be inves-tigated in vitro as a first step.

Dermal rat (in vivo) and/or in vitro rat/human dermal absorption.

OPPTS 870.7600 OECD 427, 428

If dermal pathway needs to be refined. Comparative oral and dermal ADME stud-ies on absorption and excretion rates, par-ent and metabolite distribution could better characterize the route PK differences and interpretation of oral toxicity data if re-quired.

Special endpoint studies

Special toxicities should be addressed if an issue occurs during testing or an issue is raised regarding chemical class or mode of action (e.g., neurotoxicity and AChE inhibi-tion, alteration of ion channels, or GABA agonism/antagonism; endocrine toxicity and estrogen or androgen receptor binding and gene activation, disruption of thyroid homeostasis; immunotoxicity and inflam-mation). Mode of action data may be helpful for re-fining assessment, human relevance and addressing uncertainties. (see WHO guid-ance at http://www.who.int/ipcs/methods/harmonization/areas/cancer/en/. )

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Single dose study OECD No. 124 (Guidance for the Derivation of an Acute Reference Dose) OPPTS 870.6200

If there is a need based on the intrinsic properties (endpoint of concern) of the chemical and on the magnitude of acute exposure. There are vector control scenarios that would result in acute exposure (see Table 2). If effects are observed from repeated dose studies that could arise from a single exposure, as first tiered, the ARfD could be based on that repeat dose study.

Note: Acute and 90 day neurotoxicity and 28 day immunotoxicity studies are US EPA requirements for nonfood uses, but there are opportunities for read-across/bridging or waivers.

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Table 4. Ecological effects information for assessing insecticides used for vector control.

Study Study Study Study Study

Lower Tiered Data or Base Set of Studies

Avian acute oral toxicity

OPPTS 850.2100 OECD 223

TGAI Larviciding/outdoor space spray, indoor residual spray-ing/Nets (Sweeping floors to outdoors)

Calculations to as-sess potential expo-sure to be conducted as a screening step. Recommend testing only if a potential ex-posure is predicted based on conserva-tive exposure calcu-lations. Alternatively can justify use of acute oral mammali-an endpoint as a sur-rogate to assess avi-an toxicity in the in-terest of miminising vertebrate testing

Acute toxicity to freshwater fish

OECD 203

TGAI, EUP Washing bed Nets/disposal of net treatment solution, larviciding/outdoor space spray

Acute toxicity freshwater inver-tebrates (Daphnia magna)

850.1010 OECD 202

TGAI, EUP Washing bed Nets/disposal of net treatment solution, larviciding/outdoor space spray

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Toxicity to fresh-water alga

OECD 201

TGAI, EUP Washing bed Nets/disposal of net treatment solution, larviciding/outdoor space spray

Higher Tiered Data or Conditional Studies (based on significant hazard and exposures to the habitat)

Early lifestage, freshwater fish

OECD 210

TGAI Larviciding/ Outdoor space spray

Only relevant if the substance has a high persistence or high frequency of use which would result in a continuous expo-sure

Chronic toxicity to aquatic inverte-brates (Daphnia magna reproduc-tion test)

OPPTS 850.1300 OECD 211

TGAI Larviciding/ Outdoor space spray

Only relevant if the substance has a high persistence or high frequency of use which would result in a continuous expo-sure

Whole sediment: acute freshwater invertebrates Chironomus ripar-ius

OECD 235

TGAI Larviciding/ Outdoor space spray

Relevant for sub-stances with high persistence and Koc value which indicates potential to partition to sediment

Avian reproduction test

OPPTS 850.2300 OECD 206

TGAI Larviciding/outdoor space spray, indoor residual spray-ing/Nets (Sweeping floors to outdoors)

Only relevant if the substance has a high persistence or high frequency of use which would result in a continuous expo-sure

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Earthworm acute toxicity

OECD 207

TGAI, EUP Larviciding/outdoor space spray, indoor residual spray-ing/Nets (Sweeping floors to outdoors)

Calculations of po-tential exposure to be conducted to de-termine if exposure to soil is significant from the intended use.

Earthworm repro-duction test

OECD 222

TGAI, EUP Larviciding/outdoor space spray, indoor residual spray-ing/Nets (Sweeping floors to outdoors)

Calculations of po-tential exposure to be conducted to de-termine if exposure to soil is significant from the intended use. Only relevant if the substance has a high persistence or high frequency of use which would re-sult in a continuous exposure

Soil microorgan-isms- carbon, ni-trogen transfor-mation

OECD 216 & 218

TGAI, EUP Larviciding/outdoor space spray, indoor residual spray-ing/Nets (Sweeping floors to outdoors)

Calculations of po-tential exposure to be conducted to de-termine if exposure to soil is significant from the intended use

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