Pyridaben Registrant Meeting – 03-13-2013-Nissan-Canyon-Gowan-EPA

Meeting Highlights

Nissan, Canyon, Gowan, and US Environmental Protection Agency

March 13, 2013

On March 13, 2013, at the request of Nissan, Canyon, and Gowan, the technical registrants for 

pyridaben, representatives from the companies met for one hour with US Environmental 

Protection Agency (EPA) to discuss the data requirements required in the pyridaben data call-in 

(DCI). During the presentation the registrants informed the EPA of the current status of the DCI

and proposed several modifications to the testing required for ecological effects and fate data 

requirements. The registrants indicated protocols would be submitted for the review of the EPA. 

Pyridaben:

EPA-Nissan/Canyon Meeting

March 13, 2013
Introduction

• Pyridaben

– Miticide/insecticide

– Used primarily on selected orchard crops

• Citrus

• Pears

• Pecans

• Apples

• Primary Discussion Topics

– DCI requirements

• Nissan’s proposals and rationale for addressing DCI requirements

• Environmental fate requirements followed by ecotoxicology

requirements

– Available data
Pyridaben

• Key uses 

– Citrus: 1 app/season, average 0.375 lbs a.i./A; timing depends 

on pests. Maximum allowable 0.5 lbs a.i./A.

• Pests: citrus rust mite, citrus red mite

– Pears: 1 app/season, 0.375 lbs a.i./A (mites); 1 app/season, 

0.75 lbs a.i./A (pear psylla), timing depends on pests

• Pests: mites, pear psylla

– Pecans: 1 app/season, average 0.309 lbs a.i./A, timing depends 

on pests, up to a maximum of 0.5 lbs a.i./A

• Pests: Mites and aphids

– Apples: 1 app/season, average 0.309 lbs a.i./A, timing depends 

on pests, up to a maximum of 0.5 lbs a.i./A

• Pests: Mites

– Ornamentals: Maximum single application rate 6 oz/100 gal 

(equivalent to 0.281 lbs a.i./A)
Pyridaben

• Key physiochemical properties

– Water solubility: Very low; 10-20 ug a.i./L

• Technical challenges for some studies, particularly 

studies conducted in seawater (lower solubility)

– Soil adsorption: High binding to soil/sediment

– Susceptible to photodegradation: DT50<2d

– Susceptible to microbial degradation

– Low vapor pressure

– Application methods: Ground and Airblast
EPA Ecotoxicology and Environmental 

Fate DCI Requirements

• Studies required include:

– Environmental Fate

• Aerobic soil metabolism (4 soils)

• Aerobic aquatic metabolism (2 sediments)

– Key consideration:

• EPA believes that pyridaben is persistent in the 

environment based primarily on laboratory data

• Microcosm studies indicate otherwise
Aerobic Soil Metabolism

• Several studies have been conducted on aerobic soil 

metabolism

• EPA has found deficiencies in all but one of these 

studies and has requested that testing be repeated

• Nissan initially proposes to conduct additional aerobic 

soil metabolism testing on a WA soil

– Major growth area for pome;

– Correlates with soil dissipation data;

– High probability of obtaining ‘virgin’ soil

• If results similar to previous results (route) Nissan 

proposes to reduce the number of soils used for 

additional aerobic soil metabolism testing

– Two soils total

– Testing with two labels

– Radiolabeled test material available
Aerobic Soil Metabolism

HLS Study Protocol and Questions

• Test substance: Two 14C radiolabeled forms

• Test soil: To be obtained from a site in Washington, USA

• Application rate: 1.12 kg a.i./ha (equiv. 1.12 ppm, 16 oz/A, max. 

rate )

• Conditions: At pF 2 to 2.5 at 20oC in the dark 

• Analysis: Duplicate samples per label will be taken at 

appropriate time intervals and identified and characterized if 

necessary.

• Sampling intervals: T0, 7, 14, 30, 60, 90 and 120 days

•If DT50 is >120 days, additional sampling times such as at 180, 

240, 300 and 365 days are required?

•If test interval > 120 days, concern about microbial viability

• Trapping media: Volatile metabolites including CO2 will be 

trapped and quantified.
Aerobic Aquatic Metabolism

• Aerobic aquatic metabolism previously 

conducted on two sediments

• EPA found deficiencies in previous studies and 

requested that the studies be repeated

• Nissan has concerns about microbial viability if 

use U.S. water and sediment and ship to HLS UK. 

Can EU water and sediment be used?

• Microcosm data available on the fate of 

pyridaben in aquatic systems

• Possible to use these data to address some of EPA’s 

questions concerning aquatic metabolism?
Aerobic Aquatic Metabolism

HLS Study Protocol and Questions

• Test substance: Two 14C radiolabeled forms

• Test sediment: To be obtained from two sites in USA?

In the OPPTS GL two sediments to be used for this study are strictly defined. 

• Application amount: 794 ug/vessel (equiv. 1.12 kg a.i./ha, 16 oz/A)

* The calculated concentration of pyridaben in water (110 ug/L) exceeds its 

solubility (22 ug/L). Is this acceptable?

• Conditions: Water/sediment volume ratio = 3/1 to 4/1 at 20oC in the dark 

• Analysis: Duplicate samples per label will be taken at appropriate time 

intervals and identified and characterized if necessary.

• Sampling intervals: T0, 1, 2, 7, 14, 30, 60 and 100 days

* If DT50 is >100 days, additional sampling times such as at 150, 240, 300 

and 365 days are required?

• Trapping media: Volatile metabolites including CO2 will be trapped and 

quantified.
Microcosm Data

• Nissan has conducted three different 

microcosm studies

– Two focus on effects on biota

– One focuses on fate in an aquatic system

– Nissan believes these data provide useful, 

informative information concerning the fate and 

effects of pyridaben in aquatic systems

– Results are consistent among studies

– Nissan urges EPA to use these data in its 

evaluation of pyridaben
Pyridaben

• Ecotoxicology data requirements

– Seedling emergence 

– Vegetative vigor

– Estuarine-marine fish acute toxicity (sheepshead)

– Estuarine-marine invertebrate chronic toxicity 

(mysid)

– Estuarine-marine fish chronic toxicity 

(sheepshead)

– Acute sediment toxicity

– Bioconcentration in oysters

– Field testing for pollinators
Seedling Emergence and 

Vegetative Vigor

• Tier I seedling emergence and vegetative vigor 

testing conducted at 0.5 lb a.i./A

– NOEC not obtained for three species in seedling 

emergence testing corn, lettuce, and tomato

– NOEC not obtained for four species in vegetative 

vigor testing

– Nissan propose to conduct Tier II seedling 

emergence testing with corn, lettuce, and tomato

– Nissan propose to conduct Tier II vegetative vigor 

testing with soybean, tomato, oat, ryegrass
Estuarine-marine acute toxicity

• Testing has previously been conducted on 

sheepshead minnows

– Less sensitive than freshwater species

– LC50 approximately equal to water solubility limit for 

technical pyridaben

– EFED suggested conducting testing with TEP to 

address the water solubility limitation

– Nissan willing to conduct testing with TEP

– Question: TEP is a wettable powder, how does this 

resolve solubility issue?

– Question: How will EFED conduct the risk assessment 

if results with TEP indicate LC50>water solubility limit?

• Validity of RQs calculated with toxicity data > water 

solubility?
Mysid Lifecycle Testing

• Does the non-persistence of pyridaben under use 

conditions enter into decision concerning these data 

requirements

• Conditional data requirements according to 40CFR

• Existing mysid acute study

 NOEC=0.14ug a.i./L, LOAEC=0.18 ug a.i./L

• Existing mysid lifecycle study: NOEC = 0.13 ug a.i./L

– EFED requested a repeat study b/c NOEC = high test 

concentration

– Based on available data, next highest test concentration in 

dose scheme would be an effect concentration

– How much would be gained in repeating this test?
Sheepshead ELS Testing

• Current acute toxicity data indicates LC50>limit of 

water solubility

• Acute to chronic ratio based on freshwater 

species

– Is this a viable approach coupled with a sheepshead

acute study

• Rapid loss of pyridaben from the water column

– DT50 < 2 days

• Sheepshead less sensitive than freshwater 

species

• Re acute to chronic ratio

• Conservative value based freshwater species?
Acute Sediment Toxicity

• Nissan proposes to conduct acute sediment 

toxicity testing

• Question concerning species selection

– Guidelines indicate chironomids or amphipods as 

test species

– Plan to conduct using chironomids
Bioconcentration in Oysters

• Request based on results of fish bioaccumulation 

testing and perception of persistence

– Standard bioaccumulation testing indicated a BCF = 342 -

439; BCF from fish lifecycle testing = 1168 – 3780

– Microcosm data indicates that pyridaben not persistent in 

aquatic systems

• EPA has expressed concern about bioaccumulation in 

sediment-dwelling organisms

• Oysters are filter feeders rather than deposit feeders

– EPA’s oyster bioaccumulation guideline is similar in design 

to the standard fish bioaccumulation guideline
Bioaccumulation in Oysters

• Based on EPA concerns about sediment dwellers 

and partitioning of pyridaben to sediment, Nissan 

proposes an alternative test:

• OECD 315, Bioaccumulation in sediment-dwelling 

benthic oligochaetes

– More realistic experimental design than the oyster 

bioaccumulation test (3 compartments)

– Directly addresses bioaccumulation from the ingestion 

of sediment containing a pesticide

– Directly addresses bioaccumulation in sedimentdwelling organisms from pore water
Field Testing with Pollinators

• While Nissan recognizes this data requirement is based 

on the acute contact toxicity results, it is not clear 

whether EPA’s concern is for adults or larval stages

• Nissan has submitted a bee brood feeding study (hive 

study) to EPA to address this data requirement

• Nissan believes that this study will address EPA’s 

questions concerning effects on bees

• Nissan proposes to wait until EPA reviews the 

submitted study before conducting additional work 
Conclusion

• Nissan is moving ahead with studies to 

address the pyridaben DCI

• Nissan has previously submitted microcosm 

data that provides useful information to 

relevant to EPA’s review of pyridaben

• Nissan has proposed some modifications to 

the testing required in the DCI and appreciates 

EPA’s feedback concerning those modifications
Study initiation Study completion Final report

OCSPP850.4100

Terrestrial plant 

(seeding emergence)

08/15/2013 09/15/2013 January 2014

OCSPP850.4150

Terrestrial plant 

(vegetative vigor)

08/22/2013 09/22/2013 January 2014

OCSPP850.1075

Estaurine/marine fish 

acute

07/1/2013 07/15/2013 December 2013

OECD.315

Bioaccumulation August, 2013 October 2013 March 2014

OCSPP850.1735

Acute sediment 

organism

November 2013 November 2103 March 2014

Expected study schedule