# Best Use of Available Information in Endangered Species Assessments: Proposed Approaches with Illustrative Examples

Joy Honegger, Ph.D. Monsanto Company April 22, 2014

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# Assessing Taxa for which Toxicity of the Pesticide of Interest is Low

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# Selection of Effects Endpoint for Action Area Indeterminate LD 50 

# /LC 50

• Interim Approach for Acute Effects for Animals:

– LD 50 /LC 50 of most sensitive species or HC 05 of SSD of LD 50 /LC 50 ’s

– Using slope of dose response curve calculate concentration (or dose) that would result in a 1 in a million chance of causing mortality to an individual.



### • However, when toxicity to a taxon is low:

– LD 50 /LC 50 may be an indeterminate “>” value (little to no mortality at highest dose tested)

– No slope from a dose response curve available to calculate 1 in a million chance

– However, a NOEL/NOEC may be available from the study indicating that No Effect would be expected at highest Estimated Environmental Concentration and this information should be utilized in the assessment

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# Proposal for Taxa for which Toxicity of Pesticide of Interest is low

• Establish different criteria for NOEL/NOEC than required when a dose response curve and calculated LD 50 

## /LC 50 

## are available

– Considers the different impact of the two endpoints

– Avoids unnecessary additional vertebrate or invertebrate testing



## • If NOEL or NOEC for all tested species in a taxon is > Highest relevant EEC

– Remove taxa from further consideration of proximity to pesticide use

– Conclude “No Direct Effects”

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# Example Pesticide with Low Toxicity to Specific Taxa

• Avian LD 50 

### > 3000 mg/kg bw

– only adverse observation transient lethargy



### • NOEL = 1500 mg/kg bw

• Maximum Use Rate 1.5 lb a.i ./A

– Single Application



### • Dose

- based EEC for 20 g bird consuming short grass = 410 mg/kg bw

• NOEL (1500 mg/kg bw ) > EEC (410 mg/kg bw )

• Proposed conclusion:

– No Direct Effects

– No Proximity Assessment Required

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# Use of Biological Data to Facilitate Indirect Effects Assessment for a Herbicide

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# Biological Data Available

• Information available on T & E species

– Species characteristics

– Diet

– Habitat

– Primary Constituent Elements



## • This information could be categorized to efficiently exclude species from consideration of indirect effects

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# Flowchart for Evaluating Herbicide Indirect Effects

Proximity * of Listed Species to

Relevant Land Use in County with Crop of Interest? Review Species

- Specific Habitat and Diet Requirements

Yes

No Indirect Effect No Listed Species Plant Dependent or Plant Obligate?

Species

- County Co

- occurrences of Listed Species and Crop Identified

No

Consider herbicide properties to determine if type of plants required, for purpose required
, may be affected Yes (or Potentially)

* Proximity Distance based on Indirect Effect “no effect” distance from application area. 8

# Flowchart for Evaluating Herbicide Indirect Effects

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Consider herbicide properties to determine if type of plants required, for purpose required, may be affected

No Indirect Effect No Yes

Subsequent Evaluation to

Determine if Herbicide Use Limitations are Needed

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# Example for Assessing Indirect Effects from Selective Herbicides

• For a herbicide with only post

- emergence activity If at drift rates: Lowest Monocot EC 25 

## > EEC drift , field edge 

## Lowest Dicot EC 25 

## < EEC drift , field edge 

## But perennial species (e.g. brush and trees) are not affected at drift rates

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## Selective Herbicide Indirect Effects Example Habitat/Diet/Repro Requirements Evaluation

• Review species requirements for habitat, diet & reproduction

– If no plant requirements, conclude “No Indirect Effect”

– If plants required, review nature of requirement

• If monocot required

– Conclude “No Indirect Effect”

• If tree or brush required

– Conclude “No Indirect Effect”

• If other dicot required

– Consider if requirement is

– For dicots in general

- use EC 25 in further evaluation

– For specific plant species

– use NOEC in further evaluation

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# Species Diet and Habitat Examples

Species Primary Feeding Strategy Feeding Ecology Habitat Description

Least tern ( Sternula antillarum ) Piscivore Invertivore Eats mainly small fishes (generally less than 9 cm long), sometimes crustaceans or insects. Seacoasts, beaches, bays, estuaries, lagoons, lakes, and rivers. Nests usually in

shallow depression on level ground on

sandy or gravelly beaches and banks

of rivers or lakes, typically in areas with sparse or no vegetation

Marbled Murrulet

( Brachyramphus

marmoratus ) Invertivore , Piscivore Diet includes fishes ( sandlance , capelin, herring, etc.), crustaceans ( mysids , euphausiids ), mollusks Old growth coastal forests

Mount Graham Red Squirrel ( Tamiasciurus

hudsonicus grahamensis ) Frugivore , Granivore Diet consists of seeds, conifer cones, nuts, fruits. Occasionally feeds on invertebrates and small vertebrates Major constituent element is dense stands of mature spruce

- fir forest

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# Use of Biological Data

• A database of biological data relevant for the assessment of indirect effects should be developed

– Categorize species according to classes of taxa required for diet, habitat, temporal relationships, etc.

– Allow efficient sorting and evaluation of species requiring indirect effects assessment

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