## Illustrating Use of Simple Filters to Reduce the Scope of a National Endangered Species Assessment for a Herbicide Dwayne R.J. Moore – Intrinsik Environmental Sciences (US), Inc., New Gloucester, ME April 22 nd , 2014

# Interim Approach

• Step 1 proximity analysis

– “May affect” if overlap between species range and critical habitat and action area

– Otherwise, “No effect” 

### • Action area

– Includes potentially treated areas and off -site transport area

– Outer boundary of off -site transport area occurs where conservative estimate of exposure crosses below conservative effects metric (e.g., dose causing one - in -a - million mortality to most sensitive animal species) for the most at- risk receptor group 

### • Outcome will be an enormous number of species status records (SSRs) for listed species, many of which are not even remotely at risk 

## Cotton **Location Off** **- site transport zone**  

## Species 2 **Range Species 1**  **Range Better approach**  **would be to define**  **separate of** 

**f -** **site transport**  **areas for**  **each use pattern**  **and receptor**  **group for**  **both direct and indirect**  **ef fects** 

# Establishing Off**- site Transport**  **Areas**

• Identify toxicity thresholds for each receptor group for both direct and indirect effects • Determine distances from treated areas at which thresholds will no longer be exceeded • Exposure analyses: Drift models or field study results, T- REX, TerrPlant , PRZM/EXAMS • Effects metrics and obligate relationships

– Animals: Acute concentration or dose causing 1 - in - a - million mortality either for most sensitive species or HC05; most sensitive chronic NOEC

– Plants: Lowest of NOAEC and EC05 

## • Indirect effects metrics

– Animals : Acute concentration or dose affecting 10% of individuals from HC05 hypothetical species or most sensitive LC/EC50; chronic LOAEC or defensible ECx

– Plants: Lowest of LOAEC and EC25 

## • Incorporate labeled risk mitigations, e.g., buffers, DRTs

# Case Study

• Widely used herbicide that provides post- emergence control of broadleaf weeds, woody brush and vines • New formulation proposed, but numbers changed for this example • Assume rates vary from 0.1 to 1 lb ai/A depending on use pattern • Uses include row crops, grains, pastures, etc • Mitigations on proposed label

– Extremely coarse to ultra coarse spray drift nozzles

– Boom height ≤ 24 inches from target

– 150 ft buffer 

## • EFED has conducted full risk assessment on ai

# Use Patterns

**Use Pattern Maximum**  **Single Ap**  **plication Rate ( lb**  **ai /A** **) Number of** 

**Ap plications**  **Minimum**

**Ap plication**  **Interval (d)**  Ve getable 0.5 1 - Between crop application 1 1 - Corn and popcorn 0.5 2 14 Cotton 1 2 14 Tu rf 1 1 - Grass seed 0.125 1 - Pasture 1 1 - Conservation Reserve Program 1 2 20 Small grain 0.25 2 14 Sorghum 0.25 2 14 Soybean 1 3 14 Sugarcane 1 2 14 Sod farm 0.5 2 14

# EFED Assessment

• Terrestrial biota

– Using T- REX and TerrPlant , modeled application rates ranging from 1 - 3 lb ai /A

– Proposed maximu m for new formulation = 1 lb ai /A

– RQs > Listed Species LOC for acute exposure to birds (on -field), but not for chronic exposure

– RQs > Listed Species LOC for chronic exposure to mammals (on -field), but not for acute exposure

– RQs > 1 for terrestrial plants for nearly all use patterns 

## • Aquatic biota

– No RQs exceeded listed species LOCs for fish, aquatic invertebrates, non vascular plants or vascular plants at application rate of 1 lb ai /A 

## • No need to conduct proximity analyses for direct effects to listed aquatic species or for listed species that depend on aquatic prey and habitat

# Additional Filters

• Determine off

-site transport area for remaining receptor groups

– Used actual spray drift curve from field study conducted with DRT nozzle

– Incorporated no -spray buffer of 150 ft 

## • Used Proximity Distance Calculator

– Determines distance to toxicity threshold for each use pattern/receptor group

– For terrestrial biota, replicates T- REX and TerrPlant

– For aquatic biota, uses outputs from PRZM/EXAMS

– Adjusts results for distance from field assuming spray drift curve and buffer size 0 0.001 0.002 0.003

0 200 400 600**F r** **a c** **t i** **o n** **o f** **A p** **p l** **i e** **d**

**Distance (feet)** Raw Data Model

# Results

**Maximum Single Ap**  **plication Rate (**  **lb /A**  **Crops Exposure at**  **Dow nw**  **ind Field Edge (**  **lb ai**  **/A )**  **Potentially at Risk?**  **Ac tion A** **rea**

**(Distance Bey ond**  **Field Edge, feet) Monocots**  **Dicots** 0.125 Grass seed 0.000049 No No NA 0.25 Sm all grain and sorghum 0.000098 No No NA 0.5 Vegetable, sod farm 0.000196 No No NA 1 Pasture, cotton, CRP, soybean, sugarcane 0.000392 No Yes 116 

## • For direct effects to listed bird and mammal species

– Concerns only exist for treated areas of field assuming 100% foraging in those areas

– No concern beyond field edge 

## • Relative rarity of wi ldlife foraging exclusively on treated portions of crop fields also precludes effects to listed species that depend on wi ldlife for prey • Terrestrial plant results shown below

# Results, continued

**Ta xon**  **EP**

**A Step 1**  **Determination Our Direct** 

**Effects Determination**  **Our Indirect**

**Effects Determination**  **Comments** Mammals, b irds, reptiles and terr. amphibians May affect May affect May affect Only listed species that forage in treated areas or that depend on listed dicots are potentially at risk Te rrestrial invertebrates May affect No effect May affect Concern is only for listed species that depend on dicots Te rrestrial monocots May affect No effect No effect Te rrestrial dicots May affect May affect No effect Only for highest application rate Freshwater fish and aq. amphibians May affect No effect No effect Estuarine and marine fish May affect No effect No effect Freshwater invertebrates May affect No effect No effect Estuarine and marine invertebrates May affect No effect No effect Aquatic vascular plants May affect No effect No effect Aquatic non -vascular plants Not applicable because there are no listed non -vascular plants

# Case Study Conclusions

• Using interim approach, all listed species within 116 feet of labeled uses would screen through to Step 2 • No concern for listed bird and mammal species that do not forage on treated areas • No concern for listed species that depend on birds and mammals for prey • No concern for listed monocot species or listed species that depend on monocots for food and habitat • Proximity analysis only necessary for:

– Listed dicot species and the species that depend on them

– Only for use patterns with maximum application rate of 1 lb ai /A 

## • Overall, scope of assessment considerably reduced through use of simple, conservative filters