OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

RE: Meeting between Dow AgroSciences (DAS) and EPA to Discuss DAS’ Recently 

Completed Chlorpyrifos Higher Tier Ecological Risk Assessment

List of Documents

1. Meeting Summary Page 1

2. Meeting Sign in Sheet Page 2

3. DAS PowerPoint Presentation Page 3

Meeting Summary

On Wednesday, August 21, 2013, EPA’s Office of Pesticide Programs met with Dow 

AgroSciences (DAS) and their consultants for a presentation of DAS’ recently completed

chlorpyrifos higher tier ecological risk assessment. Due to the breadth of the material covered in 

their risk assessment, the presentation touched on only a few areas. Some of the areas that were 

presented were fate in the environment and long-range atmospheric transport, refined avian risk 

assessment for flowable and granular formulations, exposures and risks to aquatic organisms, 

and risk to pollinators. The DAS ecological risk assessment did not address endangered species.

8/21/2013

1

1

DOW CONFIDENTIAL - Do not share 

without permission

Authors – Panel Members

John P. Giesy1, Keith R. Solomon2, Donald 

Mackay3, Jeffery M Giddings4, Marty Williams5, 

Dwayne Moore6, John Purdy7, Chris Cutler8

1. Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada

2. Centre for Toxicology, School of Environmental Sciences, University of 

Guelph, Guelph, ON, Canada.

3. DMER, Peterborough, ON, Canada

4. Compliance Services International, Rochester, MA, USA

5. Waterborne Environmental, Leesburg, VA, USA

6. Intrinsic Environmental Services, New Gloucester, ME, USA

7. Abacus Consulting Services Ltd., Campbellville, ON Canada

8. Department of Environmental Sciences, Faculty of Agriculture, Dalhousie 

University Truro, NS, Canada

2
8/21/2013

2

Communication to the scientific 

community

►Six peer-reviewed papers in Reviews of 

Environmental Contamination and 

Toxicology plus an overview paper –

executive summary (accepted or in 

revision).

►Special symposium at the ACS meetings 

in Indianapolis on Sept 10, 2013

►Other presentations, such as at SETAC

3

Outline

►Approach

►Properties and uses of chlorpyrifos in the United States

►Fate in the environment and long-range atmospheric 

transport of the organophosphorus insecticide, 

chlorpyrifos and its oxon

►Refined avian risk assessment for flowable and granular 

formulations of chlorpyrifos in North America

►Exposures of aquatic organisms resulting from the use of 

chlorpyrifos in North America

►Risks to aquatic organisms from the use of chlorpyrifos 

in North America

►Risk to pollinators from the use of chlorpyrifos in North 

America

4
8/21/2013

3

Approach

►Build on the previous assessments

Giesy JP, Solomon KR, Coates JR, Dixon KR, Giddings JM, Kenaga EE. 1999. 

Reviews of Environmental Contamination and Toxicology 160:1-129

Solomon KR, Giesy JP, Kendall RJ, Best LB, Coats JR, Dixon KR, Hooper MJ, 

Kenaga EE, McMurry ST. 2001. Human and Ecological Risk Assessment 7:497-

632

5

Approach

►Build on the previous assessments

►Focus on current uses supported by DAS (agricultural)

►Focus on new label rates and directions

►Focus on refined upper tiers of risk assessment, (no 

simple hazard quotients)

►Use new methods for assessing risks - models

►Exposures and risks to birds

►Exposures in surface waters

►Respond to newly identified concerns

►Potential for long-range transport

►The active metabolite, chlorpyrifos-oxon

►Risks to pollinators

►POPs and PBT (Issue raised in POPSRC and EC 1107/2009)

6
8/21/2013

4

Overview of conclusions 1

►Degradation is generally rapid at rates used in 

agriculture.

►Important and widely used in agriculture.

►Use has decreased by about 50% since 2000 does not 

show strong seasonality.

►Concentrations in semi-remote locations less than 

toxicity values.

►Characteristic Travel Distance is between 62 and 244 

km. 

►CPY does not trigger POPs or LRT. CPYO triggers LRT 

only but POV is small and shows that LRT is not an issue.

►CPY triggers T but not P or B under EC 1107.

7

Overview of conclusions 2

►Models for exposure to liquid and granular formulations 

based on refinements of TIM V1 and 2.

►For flowable CPY, some acute risks for sensitive birds 

and greater rates of application – for most birds and 

most uses risks are de minimis.

►Chronic risk not an issue.

►Risks from granular de minimis for all species.

►Field and incident data consistent with conclusions of 

model.

►Concentrations of CPY in surface water have declined 

since before 2000.

►CPYO not measurable in surface waters.

8
8/21/2013

5

Overview of conclusions 3

►Modeled exposures consistent with measured values in 

focus watersheds (GA, MI, CA). Median durations above 

0.1 μg/L were ≤ 2 d.

►Risks to aquatic organisms have decreased since 2000.

►Risks from CPY in benthos and CPYO de minimis.

►Risks from CPY in aquatic organisms de minimis except 

for low risks in Crustacea in high-use CA focus watershed.

►Consistent with incident reports.

►CPY is toxic to bees by direct contact - mitigated by label.

►Nectar and pollen most important routes of exposure but 

little risks predicted by Tier-2 assessment.

►Negligible risks from water, propolis, and wax.

►Incident reports rare, especially after 2000.

9

Properties and uses of 

chlorpyrifos in the United States

RA 2

10
8/21/2013

6

Purpose

►Provide background information for discussion in 

the other chapters

►Chemical and physical properties

►Metabolites and breakdown products

►Dissipation

►Mode of action

►Formulations

►Use and timing

11

Chemical and physical properties

►Fate in air and long-range transport – see RA 3 

(Mackay et al, 2013).

►Fate in water, soil, and sediments

►Build on previous papers (Racke 1993) and 

Gebremariam et al. 2012.

►Select most appropriate values to inform the 

ERA and modeling.

12
8/21/2013

7

N

Cl

Cl

Cl

P O

S H3C H2C O

H3C H2C O

N

Cl

Cl

Cl

P O

O

H3C H2C O

H3C H2C O N

Cl

Cl

Cl

P O

S

H3C H2C O

HO

N

Cl

Cl

Cl

HO

N

Cl

Cl

Cl

H3C O CO2

, N2, ClCPY, chlorpyrifos

Desethyl chlorpyrifos CPYO, chlorpyrifos-oxon

TMP, trichloromethoxypyridine

TCP, trichloropyridinol

Transformation, metabolism and 

degradation

13 Figure 1

Physical

Parameter Values for Chlorpyrifos

Chemical Name O,O-diethyl o-(3,5,6-trichloro-2-pyridyl 

phosphorothioate

Chemical Abstracts Service 

(CAS) Registry Number

2921-88-2

Empirical formula C9H11Cl3NO3PS

USEPA Pesticide Code (PC #) 59101

Smiles notation S=P(OC1=NC(=C(C=C1Cl)Cl)Cl)(OCC)OCC

Molecular mass 350.6 g mol-1

Vapor pressure (25 °C) 1.73 x10-5torr

Water solubility (20 °C) 0.73 mg L-1

Henry’s Law Constant 1.10 x 10-5 atm m-3 mol-1

Log KOW 5.0

14 Figure 1
8/21/2013

8

Chemical

Parameter Values

Hydrolysis (t1⁄2) pH 5: 73 d

pH 7: 72 d

pH 9: 16 d

Aqueous photolysis (t1⁄2) 30 d

Aerobic soil metabolism (t1⁄2) 1.9 -1576 d

Aerobic aquatic metabolism (t1⁄2) 22 - 51 d

Anaerobic soil metabolism (t1⁄2) 15 and 58 d

Anaerobic aquatic metabolism (t1⁄2) 39 and 51 d

Soil adsorption coefficient KOC 973 – 31,000 mL g-1

Terrestrial field dissipation (t1⁄2) 1.3 - 120 d

15 Figure 1

Measured CPY

Aerobic soil 

metabolism 

Labile CPY Adsorbed 

CPY

Metabolites

F1

F2

F3

Biphasic degradation in soil

5

100 200 300 400

4

3

2

0

1

0

Time (d)

Ln % concentration

Dissipation in Barnes soil (Bidlack, 1979)

Phase I, t 1⁄2 = 25.3 d

Phase II, t 1⁄2 = 154 d

16 Figure 2 & Figure SI C-1
8/21/2013

9

Half-lives calculated from 2-

compartment model

Soil Reported t1⁄2 Calculated t1⁄2 from 2-

compartment model

Group

Commerce, MI 11 11 2

Barnes, ND 22 22 2

Miami, IN 24 18 2

Caitlin, IL 34 28 2

Marcham, UK 43 9 2

Thessaloniki, GR 46 31 1

Charentilly, FR 95 93 1

Norfolk, VA 102 57 1

Stockton, CA 107 96 1

Cuckney UK 111 84 1

German 2:3 141 99 1

17 Table 3

pH-dependence of degradation in 

soil

Group-1 soils; half-lives >30 days and pH dependent (abiotic degradation)

Group-2 soils; shorter half-lives with much weaker correlation to pH (biotic 

degradation)

18

pH

5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5

Half-life (d)

0

20

40

60

80

100

120

Group 1

Group 2

Figure 2
8/21/2013

10

Time (days)

0 100 200 300 400

Residues (% of applied radioactivity)

0

20

40

60

80

100

Adsorbed CPY

Dissolved CPY

Measured CPY

Metabolites

ModelMaker optimization results –

Barnes soil

Figure SI C-3

Half-lives chosen for the modeling 

in surface waters

►The highest half-life among the US soils in each 

group was selected as a conservative value to 

represent the group in the PRZM/EXAMS model 

runs

►Stockton (CA) soil 96 d

►Caitlin soil (IL) 28 d

20
8/21/2013

11

Cl N

Cl Cl

O P

S

O CH2 CH3

O CH2 CH3

Chlorpyrifos Chlorpyrifos-oxon

[O]

AChE

k OH

1

k3

Phosphorylation k2

AChE

O P

O

O CH2 CH3

O CH2 CH3

AChE

OH

Hydrolysis and 

reactivation

Cl N

Cl Cl

O P

O

O CH2 CH3

O CH2 CH3

AChE

O P

O

OH

O CH2 CH3

k-1

Aging (hydrolysis)

Aged enzyme cannot 

be reactivated

Recovered enzyme 

returns to normal 

function

Cl N

Cl Cl

OH

TCP

+

Mechanism of action

21 Figure 4

Relevance of MoA

►Animals with AChE are the most sensitive

►Plants much less sensitive

►Some groups of animals are more sensitive than 

others

►Metabolism to less toxic substances (TK)

►Rate of recovery (TD)

22
8/21/2013

12

Interactions with other pesticides

►With other AChE inhibiting insecticides.

►Additivity based on potency.

►With other pesticides that induce activation of 

CPY to CPYO (e.g., atrazine).

►Requires temporal co-occurrence at appropriate 

concentrations.

►Probability of co-occurrence is small – excluded 

from the assessment.

Cl N

Cl Cl

O P

S

O CH2 CH3

O CH2 CH3

Chlorpyrifos Chlorpyrifos-oxon

[O]

Cl N

Cl Cl

O P

O

O CH2 CH3

O CH2 CH3

23

Products evaluated and use

►Lorsban-4E, -Advanced, -15G, and -50W. 

►One of the most widely used insecticides 

(globally)

►Estimates of annual use in the USA since 2008 

range from 3.2 to 4.1 M kg

►Decrease of 50% since 2000

►No more residential or landscape uses

►Changes in agricultural production (GMO) and the 

introduction of new insecticides 24
8/21/2013

13

Use per crop (2007)

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1,600,000

1,800,000

2,000,000

More than half of use is 

in soybeans and corn

Pounds

From Table 4 25

Timing (cropped all year)

Crop and location

Months of the year in which CPY is applied

J F M A M J J A S O N D

Alfalfa, warmer states (CA, AZ, etc.)

Cooler states

Southern MO

Northern MO

Apple tree trunks

Asparagus CA only Southern desert

Delta

Central coast

Other U.S.

Brassica (cole) leafy vegetables

Brussels sprouts

Carrots for seed OR & WA

Christmas tree

Citrus orchard floors

Subset of Table 5 26

►No strong seasonality to the use of CPY
8/21/2013

14

Timing (cropped part of year)

Usual Planting and Harvesting Dates for U.S. Field Crops

Crop in field, location, and use of CPY

Months of the year in which CPY is applied

J F M A M J J A S O N D

Corn, Southern states in field

Use of CPY

Northern states in field

Use of CPY

Cotton, Southern areas in field

Use of CPY

Northern areas + CA in field

Use of CPY

Peanuts, in field

Use of CPY

Peppermint and Spearmint, in field

Use of CPY

Subset of Table 6 27

Timing

►Timing in relation to local conditions can 

influence fate in the environment.

►No strong seasonality to the use of CPY

►Somewhat greater use in the winter months in tree 

crops in California

►Somewhat greater use in the summer field crops 

such as corn in the summer months

28
8/21/2013

15

The bottom line

►In general, short dissipation times via:

►Volatilization,

►Photolysis,

►Abiotic hydrolysis,

►Microbial degradation

►Degradation varies with rate of use

►Degradation more rapid in field than laboratory

►Not systemic

►Important and widely used in agriculture

►Use has decreased by > 50% since 2000

►No strong seasonality in use

29

Fate in the environment and 

long-range atmospheric transport 

of the organophosphorus 

insecticide chlorpyrifos and its 

oxon

RA 3

30
8/21/2013

16

0 12 24 48 96 182 364 728 1456

Concentration

Hours after entry to the environment

Soils and 

sediments 

Aquatic 

organisms 

Birds and 

pollinators 

Long-range 

transport in air

............

Photolysis and breakdown in the troposphere and on surfaces

Absorption and adsorption to soils and sediments

Degradation by chemical and biological pathways

Fate

Figure 1 31

Occurrence of CPY in air

Location and dates of sampling Concentration (ng m-3)

CANCUP data for 8 sites in Canada 2004-

5, values range from areas of application 

to distant areas

0.08 to 22

Passive air samples in Ontario 2003-5 0.0003 to 0.06; median 0.007; 73% Frq. of Dtctn.

Iowa 2000-2 Average 1.0, 19% FOD 1.4 at 1A - AMSite , 0.88 

at Hills

Mississippi River Valley 1994 0.43

Chesapeake Bay 2000 0.015 - 0.670 Median 0.110 FOD 87%

Bratt’s Lake (Saskatchewan close to area 

of use)

Abbotsford (British Colombia, lesser use) 

10 to 100 with 3 concentrations exceeding 100 and 

a maximum of 250 in Aug 2003

Concentrations all < 0.26 in 2004 and 2005.

Mississippi River Valley FOD 93, MS 35%, Iowa City 90%, Cedar Rapids 

50%, Minneapolis 10%, Princeton MN 3%

Central Valley (CA) and Sierra Nevada, CPY up to 180 and CPYO up to 54, lesser 

concentrations in Sequoia NP.

CPY and CPYO in air in Sequoia NP 0.16 to 17.5

Table 1

32
8/21/2013

17

Occurrence of CPY in rain and snow

Location and dates of sampling Concentration in ng L-1

Chesapeake Bay 2000 Rain; 0.97 - 29 average 4.8, FOD 14%.

Wet flux, 190 ngm-2 event Total 6100 ng m-2, 

1.1 kg/year

Svalbard Ice Cap 1979 –1986 Ice, peak concentration 16.2 at ~ 15 m

Delaware/Maryland April - Sept 2000 

- 2003

Rain; 1.0 to 29 average 1.0 39% FOD.

Fluxes ~ 610-1750 average 1.0-4.5 ng m-2

7 US National Parks March-April 

2003

Snow in Sequoia NP; 2.8, 1.3

Other National Parks; 0.033 ~ 0.05 ~ 0.5 ~ 

0.02 ~ 0.02 and 0.03

Deposition in Sequoia NP; 2600 ng m-2

Other parks; 25, 65, 35, 30, 14, and 4 ng m-2

Correlations with altitude and distance, 75, 

150, 300 km from sources

Table 2

33

Occurrence of CPY in other media

Location and dates of sampling Concentration in ng g-1dw unless indicated otherwise

Sierra Nevada CA 2785 to 3375 

m elevation 2004/5

Water; all concentrations in water were <0.07 ng L-1

Sediment;

0.043 to 3.478 median 0.107.

0.285 to 12.44 median 1.73.

0.011 to 2.276 median 0.101.

0.499 to 10.717 median 1.372.

Tadpoles;

2.224 to 156, median 22.2 ng g-1lipid

2.741 to 68.4, median 19.9 ng g-1lipid

Lassen National Park, CA, 25 km 

from the San Joaquin Valley 

edge

Tadpoles of Pacific tree frog (Hyla regilla);

10 to 17 ng g-1ww

Kaweah, Kings, and Kern

Watersheds 43-85 km from the 

San Joaquin Valley edge

Tadpoles of Pacific tree frog (Hyla regilla);

<0.6 ng g-1ww

Thirty Canadian lakes 1999 -

2001

Lake water appln region; 0.28 -1.0 mean 0.65 ng L-1.

Lake water remote regions <0.017-2.9 mean 0.82 ng L-1.

Lake water, subarctic; <0.017- <0.017 ng L-1

Lake water, arctic; <0.017-1.6 mean 0.27 ng L-1.

Ontario 2003/5. Lake water; <0.002 to 0.5 ng L-1 median 0.02, 77% FOD.

Rain; <0.004 to 43 ng L-1 median 0.76, 80% FOD.

Zooplankton; <0.003-0.08, GM 0.004, 0.005 ng g-1ww.

BAF in Zooplankton (GM) 70 (ww), 3300 (lipid wt). Table 3

34
8/21/2013

18

Occurrence of CPY in other media (2)

Location and dates of sampling Concentration in ng g-1dw unless 

indicated otherwise

Chesapeake Bay, 2000 0.51-4.6 

Lichen in Yosemite NP 2003 - 2005 0.92 ng g-1, 1.7 ng g-1

Pine needles in Sequoia NP, 1994 10-125 ng g-1dw

Sequoia NP, 1996-1997 Dry deposition; 0.2-24ng m-2 day-1.

Surface water 0.2-122 ng L-1.

Table 3

35

Summary of measured values in semiremote locations 

From Table 4

36

Air

μg m-3

Rain

μg L-1

15

14

36

27

8

Snow

μg L-1

Water

μg L-1

Sediment

μg g-1

Soil

μg g-1

Biota

μg g-1

ug

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

20

40

20

20

0

11

17

11

61

0

0

46

27

10

17

0

20

40

40

0

0

0

100

0

0

0

10

10

80

0

?

HC5 Crustacea

H. azteca 

LC50

?

Toxicity 

values

Percent 

of 

samples
8/21/2013

19

Key physical chemical properties 

modeling LRT

Property of CPY Units Value

Melting point (mp) °C 42

Molar mass g/mol 350.6

Fugacity ratio (FR) - 0.68

Vapor pressure (VP) of solid Pa 0.0023

Vapor pressure of sub-cooled liquid Pa 0.0034

Solubility of solid in water g m-3 or mg L-1 0.73

Solubility of sub-cooled solid g m-3 1.07

Henry’s Law constant Pa m -3 mol-1 1.11

Air-water partition coeff. KAW - 0.00045 Log is -3.35

Octanol-water partition coeff. KOW - 100,000 Log is 5.0

Octanol-air partition coeff. KOA - 2.2 ×108 log is 8.34

Organic carbon-water partition coeff. 

KOC

L/kg 8,500 Log is 3.93

Table 5

37

Reaction half-lives (CPY for LRT)

Medium Value Comment

•OH radical reaction in air 9.1 x 10-11 cm3 

molecules-1 s

-1

2

nd order rate 

constant

Half-life in air 1.4 h,

3.0 h

•OH radical conc. of 

1.5 × 106 m-3

•OH radical conc. of 

0.7 × 106 m-3

Half-life in soil 7 to 30 d 168-720 h

Half-life in surface water 30 to 50 d 720-1200 h

Half-life in sediment 50 to 150 d 1200-3600 h

Table 6

38
8/21/2013

20

Properties of CPYO (for LRT)

Property Value 

Molar mass 334.6

Vapor pressure 0.00088 Pa

Solubility in water 26 mg L

-1

Octanol water partition 

coefficient KOW

776

Log is 2.89

Half-life in air 11 d

Half-life in soil 9 to 30 d

Half-life in water 13.2 d

Half-life in sediment 132 d

Table 7

39

TAPL3 LRT model (t 1⁄2 = 3 h)

CTD = 62 km

CTD = 244 km t1⁄2 = 12 h 40

Figure 2
8/21/2013

21

Distance (km)

0 200 400 600 800 1000

Concentration (ng m-3

)

10-5

10-4

10-3

10-2

10-1

100

101

102

Chlorpyrifos 

Chlorpyrifos-oxon 

0 2 4 8 12 16 20 67 Hours

Medium-range transport

Figure 4

CTD = 62 km

41

TAPL3 LRT model (t 1⁄2 = 12 h)

CTD = 244 km 42

Figure 3
8/21/2013

22

The bottom line

►CPY and CPYO detected in various 

environmental media

►Mass balance model

►Some transport over shorter distances

►Transformation to CPYO in atmosphere

►CPY is better parameterized than CPYO

►Concentrations, in semi-remote locations, not of 

toxicological concern

43

POPs and PBTs

Criteria for POPs

UNECE, 1996; UNEP, 2001

Criteria for 

persistence (P)

Criteria for 

bioaccumulative (B)

Criteria for 

toxicity (T)

Potential for longrange transport 

(LRT)

Water: DT50 > 

60 d

Sediment: 

DT50 > 180 d

Soil: DT50 > 

180 d

BCF > 5,000 or Log 

KOW > 5

Other, e.g., very 

toxic or 

bioaccumulation in 

nontarget species

No specific 

criteria other 

than “significant 

adverse effects”

Air: DT50 > 2 d or 

modeling or 

monitoring data 

which shows 

long-range 

transport

44

Table 12
8/21/2013

23

Criteria for PBT (EC1107/2009)

Persistence (P) Bioaccumulation 

(B)

Toxicity (T)

Marine water: t1⁄2 > 60 d;

Fresh water t1⁄2 > 40 d

Marine sediment: t1⁄2 >180 d

Freshwater sediment: t1⁄2 > 

120 d

Soil: t1⁄2 >120 d

BCF > 2,000 in aquatic 

species

Chronic NOEC < 

0.01 mg/L or is a 

carcinogen, 

mutagen, or toxic for 

reproduction, or 

other evidence of 

toxicity

Off J Europ Commun 52:1-50.

Which values are compared to the criteria?

EC 1107/2009 does not provide guidance.

Because of averaging in the environment, mean or 

geometric mean values have been recommended 

(SANCO, 2012). 45

Table 12

Half-life in water

Half-life of chlorpyrifos in water (d)

0.1 1 10 100 1000 10000

Percent rank

1

2

5

10

20

30

50

70

80

90

95

98

99 ►T 1⁄2deg from 1.5 

to 142 d, pH 5 - 9

►pH and Cu++ the 

main drivers

►GM = 29 d

►T 1⁄2dis in field = 4 -

10 d

►GM = 5 d

Geomean values do 

not trigger the 

criteria for POPs or 

BPTs

29

46 SI Table 1
8/21/2013

24

Half-life in soils

►T 1⁄2 from 1.9 to 

1,575 d in the 

laboratory and 1.5 

to 120 d in the field.

►Lab GM = 32

►Field GM = 22

►Temp and pH major 

drivers

Geomean values do 

not trigger the criteria 

for POPs or BPTs

Half-life of chlorpyrifos in soil (d)

0.1 1 10 100 1000 10000

Percent rank

1

2

5

10

20

30

50

70

80

90

95

98

99

Laboratory

Field

L 32 F 22

47 SI Table 2 & 3

Half-life of chlorpyrifos in sediment (d)

0.1 1 10 100 1000 10000

Percent rank

1

2

5

10

20

30

50

70

80

90

95

98

99

Half-life in sediments

►T 1⁄2 from 6 to 223 d 

in laboratory.

►GM = 39

Geomean values do 

not trigger the criteria 

for POPs or BPTs

39

48 SI Table 4
8/21/2013

25

BCF

BCF of chlorpyrifos in aquatic organisms

10 100 1000 10000 100000

Percent rank

1

2

5

10

20

30

50

70

80

90

95

98

99

Laboratory

Field

►BCF from 396 to 

5100 in the 

laboratory and 100 

to 4667 in the field.

►Lab GM = 848

►Field GM = 935

Geomean values do 

not trigger the criteria 

for POPs or BPTs

L 848 F 935

49 SI Table 5

POPs and long-range transport

►Not a POP on the basis of P, and B.

►No “significant adverse effects” in areas of use 

or remote regions.

►The half-life of CPY in the atmosphere does not 

exceed the trigger value of 2 d for LRT.

►CPY is found at distances from areas of 

application and even in remote locations but the 

concentrations in air, rain and snow, and aquatic 

and terrestrial media, and biota are small and 

less than the threshold of toxicity for terrestrial 

and aquatic organisms.

►Does not trigger LRT

50
8/21/2013

26

CPYO as a POP

►CPYO does not trigger the criteria for persistence in 

water, soil, or sediment.

►No data were available for BCF, but studies with 

ring-labelled CPY provide equivalency for CPYO –

does not trigger B.

►Toxicity for CPYO subsumed in that of CPY and it 

does not trigger “significant adverse effects”.

►Half-life in air is >2 d – triggers LRT

►Found at moderate distances from areas of application

►Concentrations in environmental media < threshold of 

toxicity for terrestrial and aquatic organisms.

►Partitioning to and reactivity in water reduces POV, LRT 

not an issue. 51

PBT (EC 1107/2009)

►Does not trigger P and B.

►The most sensitive chronic NOEC reported for 

aquatic organisms of 0.005 μg L-1 and triggers 

the T criteria for PBTs.

►Since CPY is an insecticide, this is expected.

►The key question is the relevance of this to exposures 

in the general environment and the lack of significant 

adverse effects from the ERAs for birds, pollinators, 

and aquatic organisms.

52
8/21/2013

27

Refined avian risk assessment 

for flowable and granular 

formulations of chlorpyrifos in 

North America

RA 4

53

LiquidPARAM

►LiquidPARAM

►Liquid Pesticide Avian Risk Assessment Model

►Incorporates parts of EPA TIM v1 and v2 and 

many of the recommendations from the EPA 

SAPs (2001, 2004)

►Predicts fate of each of 20 birds on each of 1000 

fields during 60 days following initial application

►One-hour time step

►Probabilistic exposure and effects

►Used in ERA of flowable carbofuran

54
8/21/2013

28

Overview

►Flowable chlorpyrifos

►Exposure scenarios and conceptual model

►Avian model to assess risks of flowable CPY 

(LiquidPARAM)

►Methods and results

►Granular chlorpyrifos

►Exposure scenarios and conceptual model

►Avian model to assess risks of granular CPY 

(GranPARAM)

►Methods and results

►Other lines of evidence

►Discussion

55

Focal species

56

Common name Scientific name Feeding preferences

Abert’s towhee Pipilo aberti Insects and seeds from the ground

American crow Corvus brachyrhynchos Omnivorous and opportunistic ground 

feeder

American robin Turdus migratorius Mainly insects and fruit

Blue grosbeak Passerina caerulea Mainly insects

Common pheasant Phasianus colchicus Agricultural grains and other vegetation, 

insects, and seeds

Dickcissel Spiza americana Ground-dwelling arthropods and seeds

Horned lark Eremophilia alpestris

Almost entirely of seeds in the winter 

months, but also includes ground-dwelling 

insects in the spring, summer and fall

Indigo bunting Passerina cyanea Seeds, berries, and insects gleaned from 

foliage

Killdeer Charadrius vociferous Almost entirely arthropods with a small 

portion of seeds

Mourning dove Zenaida macroura Only seeds

Northern bobwhite Colinus virginianus Insects and seeds

Red-winged blackbird Agelaius phoeniceus Insects and seeds 

Vesper sparrow Pooecetes gramineus Grasses, seeds and foliage-dwelling 

insects

Western meadowlark Sturnella neglecta Mainly insects, with a small proportion of 

seeds and grains

Table 1
8/21/2013

29

Exposure Scenarios: Lorsban Advanced

Crop Use pattern Focal bird species

Alfalfa

Southern Plains - 0.94 lb./A and 0.47 

lb/A applied broadcast with 10 d 

interval

American widgeon, Canada goose, 

Dickcissel, Mourning dove, Red-winged 

blackbird, Vesper sparrow, Western 

meadowlark

Almond

California - 1.88 lb./A applied air-blast 

post-plant 2X (May, hull-split) with 10 d 

interval

Abert's towhee, Blue grosbeak, Common 

crow, Mourning dove, Red-winged 

blackbird

Apple Northwest - 1.88 lb./A applied ai-rblast

delayed dormant to petal fall

Blue grosbeak, Common crow, Mourning 

dove, Red-winged blackbird

Broccoli

California - 2.11 lb./A applied band atplant and post-plant 3X with 10 d 

interval

Common crow, Horned lark, Mourning 

dove, Red-winged blackbird

Cherry Michigan - 1.88 lb./A applied broadcast 

post-plant

Blue grosbeak, Common crow, Mourning 

dove, Red-winged blackbird

Corn

Midwest - 1 lb./A applied broadcast atplant and band post-plant 3X with 10 d 

interval

American robin, Horned lark, Killdeer, 

Mourning dove, Northern bobwhite, Redwinged blackbird, Vesper sparrow

57 Table 2

Exposure Scenarios: Lorsban Advanced (2)

Crop Use Pattern Focal Bird Species

Grape California - 1.88 lb./A applied air-blast 

prior to bud break

Blue grosbeak, Common crow, Mourning 

dove, Northern bobwhite, Red-winged 

blackbird

Grapefruit Florida - 2.5 lb./A applied air-blast postplant (Apr-Jun)

Blue grosbeak, Common crow, Mourning 

dove, Northern bobwhite, Red-winged 

blackbird

Orange California - 5.6 lb./A applied air-blast 

post-plant (May-Aug)

Abert's towhee, Blue grosbeak, Common 

crow, Mourning dove, Red-winged 

blackbird

Pecan Georgia - 0.94 lb./A applied air-blast 3X 

with 10 d interval

Blue grosbeak, Common crow, Mourning 

dove, Northern bobwhite, Red-winged 

blackbird

Soybean

Louisiana - 0.94 lb./A applied broadcast 

post-plant 3X with 14 d interval (MayAug)

Blue grosbeak, Dickcissel, Horned lark, 

Indigo bunting, Mourning dove, Redwinged blackbird

Sweet corn

Florida - 1 lb./A applied broadcast atplant and band post-plant 3X with 10 d 

interval

Common crow, Mourning dove, Northern 

bobwhite, Red-winged blackbird 58 Table 1
8/21/2013

30

Conceptual model for exposures and 

effects of flowable CPY

59

Runoff/Erosion

Application to agricultural fields

Effects Receptors Media Routes of 

transport

Releases

Degradation to 

biologically inactive 

compounds

Uptake

Direct Spray drift

deposition

Leaching & 

sub-surface 

flow

Terrestrial biota Puddles

(invertebrates & seeds

Ingestion

Birds

Reduced 

survival

Figure 1

Hourly pesticide dose

Concentrations in food

and water over time

Fate properties

Degradation

rates

Pesticide use scenario

Initial concentrations

In food and water

Ingestion rates

over time

Hourly retained dose

Species of interest

Foraging

behavior

Rate of

metabolism

LiquidPARAM exposure

60 Figure 4
8/21/2013

31

Alive Dead

No Yes

Repeat for 20 birds

Repeat for 1000 Fields

Hourly

retained dose

Randomly select from SSD approach

dose-response curve

Yes No

Species-specific

dose-response curve?

Randomly select from

5

th, 50th and 95th centile

dose-response curves

Maximum 

retained dose

Exposure > Effects?

LiquidPARAM acute risk

61 Figure 4

Refinement of LiquidPARAM (vs. TIM 1)

►New focal species added.

►One-h time-step.

►Bird can forage on and off the field at each time-step.

►Nomograms specific to the pesticide, where data permit.

►Separate nomograms for orchards and field/row crops.

►Matrix effects considered.

►Separate RUDs for different functional groups of invertebrates 

(flying, foliage-dwelling, soil surface, below ground).

►Diets of bird species refined to 4 functional groups of 

invertebrates instead of “all invertebrates”.

►Avoidance split into gustatory and symptomatic.

►Up to 4 applications/season, model extended to 60 d, chronic 

exposure, effects, and risk can be assessed.

62
8/21/2013

32

Derivation of CPY-specific RUDs

► Only data from sprayable application studies used

► Insufficient data for row crops, RUDs for row and field crop were 

merged

► Results for field and row crops weighted to sample size

► Data collected adjacent to the field or off-field not used

► Data from dislodgeable residue measurements not used as herbivorous birds 

consume vegetative matter

► Day-0 samples used for vegetative RUDs and peak of day-0 and -

1 samples used for invertebrate RUDs

► In absence of data, used Kenaga nomogram (blue italics)

► When n = 1, standard deviation calculated from coefficient of 

variation for all other dietary items within the crop type (red bold)

► For drinking water, assumed puddles occur 1 d after application 

and that puddle concentrations equal day-1 runoff concentrations

63

Recommended RUDs

Crop type Dietary item

RUD (mg ai/kg ww/lb ai/A)

Mean Standard deviation n

Orchards

Soil surface invertebrates 1.58 0.933 13

Below ground invertebrates 0.14 0.079 1

Foliage-dwelling invertebrates 14.6 12.8 11

Flying invertebrates 0.145 0.082 1

Grass 84.8 60.3 18

Broadleaf forage 30.7 9.1 5

Seeds 0.085 0.048 1

Fruits 0.746 0.250 12

Field and row 

crops

Soil surface invertebrates 4.16 6.70 15

Below ground invertebrates 1.48 1.60 1

Foliage-dwelling invertebrates 13.7 6.77 6

Flying invertebrates 0.13 0.14 1

Grass 148 205 12

Broadleaf forage 122 68.8 5

Seeds 4.55 2.94 4

Fruits 5.52 9.8 108

64 SI Table 3
8/21/2013

33

RUDs for orchards

0.01

0.1

1

10

100

1000 RUDs (mg ai/kg-ww/lb-ai/A)

Dietary Item

Chlorpyrifos

Kenaga

65 From SI Table 3

RUDs for field and row crops

0

1

10

100

1000 RUDs (mg ai/kg-ww/lb-ai/A)

Dietary Item

Chlorpyrifos

Kenaga

66
8/21/2013

34

Avoidance studies

►Three studies available

►Wildlife International (1978) study on mallards

►Bennett (1989) study on northern bobwhite

►Stafford (2010) study on northern bobwhite

►For each study, we calculated

►% reduction in diet from treated fields due to 

adverse taste or smell

►% reduction in food intake rate due to sickness

67

Avoidance: Gustatory

y = 0.0654ln(x) - 0.3016

R2 = 0.2336

y = 0.1868ln(x) - 0.5224

R2 = 0.8948

y = 0.159ln(x) - 0.1498

R2 = 0.7984

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

0 1000 2000 3000 4000 5000

Bias to clean diet

Dietary concentration (mg ai/kg ww)

Bobwhite (Stafford, 2010)

Bobwhite (Bennett, 1989)

Mallard (Fink et al., 1980) (Wildlife International, 

1978)

68 SI Figure 6
8/21/2013

35

Avoidance: Symptomatic

0

50

100

150

200

250

300

0 10 20 30 40 50

Normalized FIR (g diet/kg bw/d)

Normalized dose (mg ai/kg bw/d)

Bobwhite (Bennett, 1989)

Stafford (2010)

Mallard (Fink, 1980) (Wildlife International, 1978)

69 SI Figure 7

Avoidance component

►Gustatory (taste or smell)

►Birds avoided treated feed at highest test concentrations

►Repellency not observed in Stafford (2010) study likely 

due to lower test concentrations

►In LiquidPARAM, we used Bennett (1989) repellency 

model because it had the strongest relationship and was 

slightly more conservative than Wildlife International 

(1978) model 

►Symptomatic (sickness)

►No apparent relationship for any of the 3 studies

►Set to zero in LiquidPARAM

70
8/21/2013

36

Effects assessment

►Used similar approach to EPA for estimation of 

acute risk (same as TIM)

►Dose-response curve for focal species with 

acceptable toxicity data

►Acute oral gavage studies only

►Canada goose, northern bobwhite, red-winged 

blackbird

►Species sensitivity approach (SSD) for 

remaining focal species (same as TIM)

►SSD based on acute oral gavage studies

►Derived hypothetical dose-response curve for bird 

species of high, median and low sensitivity

71

Species sensitivity distribution

72

Dose (mg kg-1 bw)

Proportion of species affected

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1 10 100 1000

Log-normal 

model

Figure 6
8/21/2013

37

LD50 for 5th, 50th

and 95th centile 

species derived 

from SSD for 

flowable 

chlorpyrifos

Average slope 

then used to 

generate doseresponse curves

SSDs used to derive acute doseresponse curves

73

0

25

50

75

100

0.01 0.1 1 10 100 1000

Mortality (%) 

Dose (mg kg-1 bw)

Sensitive Species (5th %ile)

Median Species (50th %ile)

Tolerant Species (95th %ile)

Sensitive species (5th centile)

Median species (50th centile)

Tolerant species (95th centile)

Figure 7Mortality per application (%)

0

1

20

30

40

LiquidPARAM 

TIM, V-1

Field – no correction

Field – correct for preappln mort. 

Field – corrected for pre-appln

mort. & control mort.

Corn (1.12 kg ha-1, 1 lb A-1) Alfalfa (1.12 kg ha-1, 1 lb A-1)

Comparison to TIM-V1 and field data 

for carbofuran

SI Figure 8
8/21/2013

38

Chronic effects metrics

►Insufficient data to derive an SSD or a doseresponse curve

►Mallard reproduction (Fink, 1978) most useful 

study

►Number of eggs per hen most important factor 

causing reduced reproductive success

►NOEC = 25 mg ai/kg diet, LOEC = 125 mg ai/kg 

diet

►Food intake rates of adult females reduced for first 

28 d of study after which they recovered to rates in 

control birds

75

Chronic effects metrics (2)

►To convert dietary concentrations to doses for 

adult females

►Calculated average food intake rate and body weight for 

females for first 28 d of study for each test concentration

►Multiplied effects concentration by normalized food 

intake rate

►NOEL = 2.88 mg ai/kg bw/d, LOEL = 18.7 mg ai/kg bw/d

►Chronic exposure duration assumed to be 28 d in 

LiquidPARAM

76
8/21/2013

39

Acute risk results for flowable CPY

►Most species at low or de minimis risk

►However, intermediate or high risk observed in 

scenarios that included:

►Highly sensitive species (5

th centile)

►Insectivores that forage extensively in treated fields 

on foliage-dwelling invertebrates

►Use patterns with large application rate

77

0

20

40

60

80

100

0 20 40 60 80 100

Species affected (%)

Mortality (%)

Example scenario for flowable CPY

in corn

Percentage of bird species affected versus percent mortality for flowable 

chlorpyrifos applied to corn (1.12 kg ha-1 or 1 lb A-1) broadcast at-plant and 

band post-plant 3X with a 10 d interval.

Figure 8

Risk

High-intermediate

Intermediate-low

Low-de minimis
8/21/2013

40

0

20

40

60

80

100

0 20 40 60 80 100

Species affected (%)

Mortality (%)

Example scenario for flowable CPY

in oranges

Percentage of bird species affected versus percent mortality for flowable 

chlorpyrifos applied airblast to oranges (6.28 kg ha-1 or 5.6 lb A-1).

Figure 9

Risk

High-intermediate

Intermediate-low

Low-de minimis

Chronic risk results for flowable 

CPY

►Could not categorize risk without dose-response 

curves

►For each bird species and use pattern, 

calculated probabilities of exceeding NOEL and 

LOEL

►Results indicated that chronic risk to birds is not 

a significant issue for flowable CPY

80
8/21/2013

41

0

20

40

60

80

100

American robin

Horned lark

Killdeer

Mourning dove

Northern 

bobwhite

Red-winged 

blackbird

Vesper sparrow

Exceedence probability (%)

Probability of Exceeding NOEL

Probability of Exceeding LOEL

Broadcast application on corn (1 lb. ai/A)

+ 2 banded applications with 10-d intervals

81

0

20

40

60

80

100

Abert's towhee

Blue grosbeak

Common crow

Mourning dove

Red-winged 

blackbird

Exceedence Probability (%)

Probability of Exceeding NOEL

Probability of Exceeding LOEL

Air-blast application on orange (5.6 lb. 

ai/A)

82

Small 

exceedence 

of the LOEL, 

- de minimis
8/21/2013

42

Conclusions for flowable CPY

►Overall acute risk to bird community is generally 

small

►Greater risk for sensitive species in fields with high 

application rates

►Chronic risk does not appear to be an issue

►Sensitivity analyses remain to be completed but likely 

that avoidance behavior not a significant factor in 

reducing risk

83

Overview

►Flowable chlorpyrifos

►Exposure scenarios and conceptual model

►Avian model to assess risks of flowable CPY 

(LiquidPARAM)

►Methods and results

►Granular chlorpyrifos

►Exposure scenarios and conceptual model

►Avian model to assess risks of granular CPY 

(GranPARAM)

►Methods and results

►Other lines of evidence

►Discussion

84
8/21/2013

43

Exposure Scenarios: Lorsban 15G

Crop Lorsban 15G Scenario Focal Bird Species

Broccoli California - 2.25 lb./A applied T-band 

at-plant

Horned lark, Red-winged blackbird, 

Mourning dove

Corn and 

sweet corn

Corn belt - 1.3 lb./A applied T-band atplant

Horned lark, Red-winged blackbird, 

Mourning dove, Northern bobwhite, 

Common pheasant

Corn belt - 1.3 lb./A applied in-furrow 

at-plant

Horned lark, Red-winged blackbird, 

Mourning dove, Northern bobwhite, 

Common pheasant

Corn belt - 1 lb./A applied broadcast

Horned lark, Red-winged blackbird, 

Mourning dove, Northern bobwhite, 

Common pheasant

Onion Pacific northwest - 1 lb./A applied infurrow at-plant

Horned lark, Red-winged blackbird, 

Mourning dove

85

Table 3

Exposure Scenarios: Lorsban 15G (2)

Crop Lorsban 15G Scenario Focal Bird Species

Peanut Southeast - 4 lb./A applied band postplant

Horned lark, Red-winged blackbird, 

Mourning dove, Northern bobwhite

Sugar beet Midwest - 1 lb./A applied broadcast atplant

Horned lark, Red-winged blackbird, 

Mourning dove, Northern bobwhite, 

Common pheasant

Sunflower Midwest - 1.3 lb./A applied T-band atplant

Horned lark, Red-winged blackbird, 

Mourning dove, Northern bobwhite, 

Common pheasant

Tobacco Southeast - 2 lb./A applied broadcast 

preplant with incorporation

Horned lark, Red-winged blackbird, 

Mourning dove, Northern bobwhite

Peanut Southeast - 4 lb./A applied band postplant

Horned lark, Red-winged blackbird, 

Mourning dove, Northern bobwhite

86

Table 3
8/21/2013

44

Runoff/Erosion

Application to agricultural fields

Effects Receptors Media Routes of 

transport

Releases

Degradation to 

biologically inactive 

compounds

Uptake

Direct 

deposition

Leaching & 

sub-surface 

flow

Conceptual model for granular CPY

Soil

Ingestion of 

particles

Birds

Reduced 

survival

87

Figure 2

GranPARAM

► Granular Pesticide Avian Risk Assessment Model 

estimates pesticide granule intake for the day 

following application

► Birds ingest grit to aid digestion

► Can mistake pesticide granules for grit

► Exposure a function of

► Availability of natural grit in crop and region of interest

► Availability of pesticide granules on soil surface

► Rates of intake of particles

► Preferences of focal bird species

► Effects component same as for LiquidPARAM

► Determines fate of each of 20 birds on each of 

1000 fields

► Chronic exposure not a concern because 

granules disappear rapidly from soil surface and 

only one granular application/season is permitted 

on the label 88
8/21/2013

45

GranPARAM: Modifications for ERA 

of CPY

►Added soil series data for 

broccoli in CA, onion in Pacific 

Northwest, sugar beet in 

Midwest, sunflower in Midwest, 

and tobacco in Southeast

►Added foraging behavior 

component

►Added SSD approach

►Updated risk categorization 

component to use area under 

the curve concept to categorize 

risk 89

GranPARAM exposure

Proportion of

pesticide granules

Crop and region

Availability of

natural grit

Species of interest

Particle

ingestion rate

Gizzard grit

count

Pesticide use scenario

Availability of

pesticide granules

Pesticide dose

Repeat for 20 birds

Repeat for 1000 fields

90 Figure 5
8/21/2013

46

Pesticide

dose

Alive Dead

No Yes

Repeat for 20 birds

Repeat for 1000 fields

Randomly select from SSD approach

dose-response curve

Yes No

Species-specific

dose-response curve?

Exposure > Effects?

Randomly select from

5

th, 50th and 95th centile

dose-response curves

GranPARAM effects

91 Figure 5

Acute risk results for granular CPY

►Less than 1% mortality for all use patterns and focal 

species

►Largely due to rarity of birds consuming pesticide 

granules

►Built-in conservatism for several input variables with 

limited data did not trigger risks

►Assumed greatest, measured particle rate of ingestion for 

all species of birds

►Bird species with softer diets or limited availability of 

natural grit will have lesser ingestions rates than assumed 

in model

►Assumed no incorporation for broadcast applications

92
8/21/2013

47

Other lines of evidence

►Field studies have been 

conducted for granular 

and flowable CPY - very 

few mortalities associated 

the treatments. 

►Incident reports – two 

reported since the 

change in labels in 2002. 

Caused by misuse.

93

Field studies - orchards

►Gallagher et al., 1994 (flowable)

►Either applied 1.5 lb.ai/A Lorsban 4E post-bloom and 6 lb.ai/A post 

petal fall or 3.5 lb.ai/A post-bloom and 4 lb.ai/A post petal fall to citrus 

groves in CA

►Only 2 treatment-related mortalities

►Selbach and Wilkens, 2008 (granular)

►Two applications of 2.1 lb.ai/A Dursban 75 WG (14-d treatment 

interval) to 3 citrus groves in Spain (no control plots)

►Up to 6.5 mg ai/kg bw chlorpyrifos measured in 3 dead birds, but no 

mortalities?

►Wilkens et al., 2008 (granular)

►Three applications of 0.86 lb.ai/A Dursban 75 WG to 1 apple orchard 

(14- and 28-d intervals) and 2 applications to 2 orchards (14-d 

intervals) (no control plots)

►No treatment-related mortalities

94
8/21/2013

48

►Wolf et al., 2010 (granular)

►Pome fruit 

• 2 applications (14-d interval) of 0.86 lb.ai/A Dursban 75 WG

• 3 applications (14-d and 28-d intervals) of 0.86 lb.ai/A Dursban 75 

WG

►Citrus fruit

• 2 applications (14-d interval) of 2.1 lb.ai/A Dursban 75 WG

►Ten carcasses recovered in total, but no deaths attributable to 

treatment of fields

►State of the art study

Field studies – orchards (2)

95

►Frey et al., 1994 (flowable and granular)

►Lorsban 4E applied at 3 lb.ai/A pre-plant and 1.5 lb.ai/A at-plant, 

whorl and tassel stages to corn crops in Iowa

►20 bird carcasses recovered; 1 may have been treatment-related

►Lorsban 15G applied at 2.6 lb.ai/A at-plant and at 0.975 lb.ai/A at 

the whorl and tassel stages to corn crops in Iowa

►14 bird mortalities, none due to treatment

►Brown et al., 2007 (flowable)

►Dursban 480 EC applied twice with a 14-d application interval and 

rate of 0.32 lb.ai/A to 8 vineyard plots in southern France (no 

control plots)

►4 avian mortalities; residues consistent with dermal exposure 

(0.27 to 1.3 mg ai/kg-bw), but not cause of death

Field studies – row crops

96
8/21/2013

49

►Moosmayer and Wilkens, 2008 (flowable)

►Dursban 480 EC applied twice with an application interval of 14 d 

and application rate of 0.86 lb.ai/A to 3 cabbage fields in Poland

►No signs of toxicity or avian mortalities were observed

►Wolf et al., 2010 (flowable)

►Applied Dursban 480 EC (2 applications; 14-d) at 0.86 lb.ai/A to 

brassica crops

►No mortalities in this state of the art study

Field studies – row crops (2)

97

Field studies – field crops (3)

►Worley et al., 1994 (flowable and granular)

►Dursban turf (liquid) and Dursban 2.5G (granular) applied twice to 

turf on golf courses in FL at 4 lb...... ai/A and interval of 21 d

►4 bird carcasses were recovered following liquid applications and 2 

following granular application. Cause of death could not be 

determined

►Clements et al., 1992 (granular)

►Spannit applied to two permanent pastures at a rate of 0.64 lb...... 

ai/A 

►Brent and Canada geese were observed feeding on the pastures 

before and after applications. No treatment-related mortalities 

occurred 

98
8/21/2013

50

The bottom line

►Flowable CPY

►According to model results, some acute risk issues for 

sensitive bird species in higher rate use patterns

►Most bird species, however, not at significant acute 

risk for assessed use patterns

►Field results and lack of incident reports suggests that 

selection of surrogate focal species in LiquidPARAM 

results in an overestimation of acute risk

►Chronic risk not a significant issue

►Granular CPY

►According to model results, de minimis risk for birds

►Field results and incident reports consistent with 

results of model

99

Exposures of aquatic organisms 

resulting from the use of 

chlorpyrifos in North America

RA 5

100
8/21/2013

51

Introduction

►Substantial monitoring of CPY in aquatic systems 

has been conducted. 

►These data are invaluable in characterizing the 

range of environmental concentrations in aquatic 

water bodies.

►However, relatively few monitoring programs have 

sufficient frequency to quantify time-series patterns 

of exposure which is necessary for understanding 

the duration and frequency of exposure to CPY.

►An argument has been made by some that the 

existing monitoring data misses short-term pulses 

that could cause adverse effects

101

Measured values CPY (surface waters)

102

Region

95th centiles of measured concentrations (μg L-1)

Agricultural Mixed Undeveloped Urban All classes

All FRRs 0.0097 0.006 0.008 0.0067 0.007

Heartland 0.018 0.005 N/Aa 0.0076 0.007

Northern Crescent N/A 0.005 0.005 0.005 0.005

Northern Great Plains N/A 0.005 0.005 N/A 0.005

Prairie Gateway N/A 0.005 0.009 0.008 0.0067

Eastern Uplands N/A 0.005 v 10.0 0.005

Southern Seaboard 0.005 0.006 N/A 0.005 0.005

Fruitful Rim 0.0086 0.022 0.005 0.0098 0.015

Basin and Range 0.005 0.005 0.01 0.005 0.009

Mississippi Portal 0.0065 0.006 0.005 0.012 0.007

Table 4
8/21/2013

52

0

0.01

0.02

0.03

0.04

0.05

0.06

1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

Year

95th centile of concentration (μg L

-1

)

Detections

95th centiles

0

10

20

30

40

50

60

Detections (% of samples)

Detections and 95th centiles of CPY 

in surface water

Figure 3

Measured values CPYO (surface waters)

104

Database

Measured concentrations (μg L-1)

Dates No. analyses Detected Range

NAWQA 1999-2012 7,098 16 0.011 to 0.054a

NASQAN 2001-2012 2025 9 0.011 to 0.036a

CA-SWD 2005-2010 288 0 N/A

WA-EIM 2009-2011 964 0 N/A

aAll less the LOD, estimated values provided
8/21/2013

53

Objective of modeling

►Modeling can be used to predict exposures in the 

absence of monitoring or extrapolate from 

monitoring data to answer questions relative to 

maximum likelihood

►To model representative environments of greaterexposure across the United States

►To characterize time-series concentrations of 

chlorpyrifos in water and sediment 

►To address return frequencies and the probability of 

missing short-term exposures that might be 

sufficiently great to cause adverse effects

105

Assessment overview

Conceptual 

model

• Wide variety of use patterns with respect to geography, crops, 

labels, and application methods

• Chemical properties - see above

• Transport pathways - runoff, erosion, spray drift, volatilization

Scenario 

selection

• Geographical focus areas - parallel examination of use density and 

a sensitivity analysis of soil-weather-crop-label combinations

• One high exposure watershed (3rd order stream) selected from 

each focus area that had a density of eligible crop

Model 

simulations

• Dry Creek, Miller County, GA – PCA=48%

• Cedar Creek, Leelanau peninsula, MI – PCA=23%

• Orestimba Creek, Stanislaus County, CA – PCA=19% 

106
8/21/2013

54

Conceptual model – use of CPY

►Granular and flowable formulations to foliage, soil, 

and dormant trees 

►Using aerial equipment, chemigation systems, 

ground boom sprayers, air-blast sprayers, tractordrawn spreaders, and handheld equipment

►Pre-plant, at plant, post-plant, or dormant season

107

Conceptual model: use of CPY

►Major crop uses (2007 data)

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1,600,000

1,800,000

2,000,000

More than half of use is 

in soybeans and corn

108
8/21/2013

55

Conceptual model: Physical properties

Parameter Values for Chlorpyrifos Source

Chemical Name O,O-diethyl O-(3,5,6-trichloro-2-

pyridyl phosphorothioate USEPA, 2011

Chemical Abstracts Service 

(CAS) Registry Number 2921-88-2 USEPA, 2011

Empirical Formula C9H11Cl3NO3PS USEPA, 2011

USEPA Pesticide Code (PC #) 59101 USEPA, 2011

Molecular Mass 350.6 g/mol Mackay, 2013

Vapor Pressure (25 °C) 1.73x10-5torr Mackay, 2013

Water Solubility (20 °C) 0.73 mg/L Mackay, 2013

Henry‟s Law Constant 1.10 x 10-5 atm-m3/mol Mackay, 2013

Log Kow 5.0 Mackay, 2013

109 Table 1

Conceptual model: Chemical properties

Parameter Values / Source Source

Aqueous hydrolysis (t1⁄2) 

pH 5: 73 d

pH 7: 72 and 81 d

pH 9: 16 d

USEPA, 2011

Aqueous photolysis (t1⁄2) 29.6 days USEPA, 2011

Aerobic soil metabolism (t1⁄2) 1.9-1576 days See Table A-1

Aerobic aquatic metabolism (t1⁄2) 22-51 days See Table A-5

Anaerobic soil metabolism (t1⁄2) 15 and 58 days USEPA, 2011

Anaerobic aquatic metabolism 

(t1⁄2) 39 and 51 days USEPA, 2011

Soil adsorption coefficient KOC 973-31000 mL/g See Table A-4

Terrestrial field dissipation (t1⁄2) 1.3-120 days See Table A-3

110 Table 2
8/21/2013

56

Selection of focus areas

Relative runoff/erosion potential Density of product Use

111

Figures 1, 5, 6, 7

Counties associated with standard 

watershed scenarios

112

Figure 7
8/21/2013

57

Sensitivity analysis

►USEPA standard pond with PRZM-EXAMS models

►Applications CPY reflect maximum label rates, minimum 

application intervals

►Used reports and extension documents provide 

additional guidance with respect to timing of applications 

►Two sets of simulations

►Simulation 1 = 28-d aerobic soil half-life (Caitlin IL)

►Simulation 2 = 96-d aerobic soil half-life (Stockton CA)

►Chemical properties consistent with USEPA guidance 

except for:

►Foliar degradation rate 3.28 d derived from measured values

►PRZM input files were modified to incorporate loss by 

volatilization

113

0

5

10

15

20

25

90th centile of estimated 96-h TWMC (μg L

-1

)

Scenario

28-d aerobic soil half-life)

96-d aerobic soil half-life)

Figure 7

Half-life and predicted concentration
8/21/2013

58

Properties used in simulations of fate in 

the environment 

Property Value Used in Model Simulations

Molecular weight 350.6 g mol-1

Water solubility (20 °C) 0.73 g mol-1

Vapor pressure (25 °C) 1.87x10-5

torr

Henry‟s law constant (20 °C) 5x10-6

(dimensionless)

Soil adsorption / desorption, Koc 8216 cc g

-1 (mean Koc from 37 data points)

Aerobic soil metabolism (t1⁄2) Run 1: 28.2 days (Catlin, IL) 

Run 2: 96.3 days (Stockton CA)

Anaerobic soil metabolism (t1⁄2) 103 d

Aqueous hydrolysis (t1⁄2)

pH 5: 73 d

pH 7: 81 d

pH 9: 16 d

Aqueous photolysis (t1⁄2) 29.6 d

Aerobic aquatic metabolism (t1⁄2) 50.8 d

Anaerobic aquatic metabolism (t1⁄2) 63 d

Foliar degradation (t1⁄2) 3.28 d

Foliar washoff (/cm) 0.1

Plant uptake 0.0

115 Table 5

Applications simulated in sensitivity analysis

Scenario

Application 

rate

(kg a.i./ha)

No. 

Apps

Interval(s) 

(d)

Date of first 

application

Application 

method CAM Incorporation depth (cm)

Application 

efficiency

Spray drift 

fraction

NYgrape11 2.4 1 - 15-Jun Drench 1 0 0.99 0.01

NYgrape21 2.4 1 - 15-May Drench 1 0 0.99 0.01

NYgrape31 1.2 1 - 15-Jun Drench 1 0 0.99 0.01

NYgrape41 1.2 1 - 15-May Drench 1 0 0.99 0.01

CAgrape12 2.1 1 - 28-Feb Drench 1 0 0.99 0.01

CAgrape22 1.1 2 195 28-Feb Drench 1 0 0.99 0.01

PAturf3

2.1, 4.2, 4.2, 

1.1, 1.1, 1.1, 1.1 7

30, 30, 30, 

60, 30, 30 14-Mar Foliar 2 0 0.99 0.01

GApecan14 4.2, 2.1, 2.1 3 10 15-Jun 1 Foliar, 2 

orchard floor 2 & 1 0 0.95 & 0.99 0.039 & 0.01

GApecan25 1.0 3 10 15-Jun Foliar 2 0 0.95 0.039

GApecan35 1.4 3 10 15-Jun Foliar 2 0 0.95 0.039

FLcitrus14

3.7, 3.7, 1.1, 

1.1, 1.1 5

30, 10, 10, 

10 10-Aug 2 Foliar, 3 to orchard floor 2 & 1 0 0.95 & 0.99 0.039 & 0.01

FLcitrus24 3.7 1 - 10-Aug Foliar 2 0 0.95 0.039

FLcitrus34 3.7 2 10 10-Aug Foliar 2 0 0.95 0.039

CAcitrus14

3.9, 3.9, 1.1, 

1.1, 1.1 5

30, 10, 10, 

10 10-Aug 2 Foliar, 3 to orchard floor 2 & 1 0 0.95 & 0.99 0.039 & 0.01

CAcitrus24 6.3 1 - 10-Aug Foliar 2 0 0.95 0.039

CAcitrus34 3.9 2 10 10-Aug Foliar 2 0 0.95 0.039

MIcherries14 3.16 3 14, 60 15-May

Trunk 

spray/lower 

branches

2 0 0.99 0.01

116 Table 6
8/21/2013

59

Applications simulated in sensitivity analysis(cont)

Scenario

Application 

rate

(kg a.i./ha)

No. 

Apps

Interval(s) 

(d)

Date of first 

application

Application 

method CAM Incorporation depth (cm)

Application 

efficiency

Spray drift 

fraction

MIcherries24 1.7 2 10 15-May Foliar 2 0 0.99 0.01

ILcorn16 1.5 1 - 15-Apr T-Band 7 4 1 0.1

ILcorn26 1.5, 1.1 2 60 15-Apr T-Band, 

Broadcast 7 & 2 4 & 0 1 & 0.95 0.1 & 0.039

ILcorn36 1.1 3 10 15-Apr Broadcast 2 0 0.95 0.039

INcorn16 1.5 1 - 1-May T-Band 7 4 1 0.1

INcorn26 1.5, 1.1 2 60 1-May T-Band, 

Broadcast 7 & 2 4 & 0 1 & 0.95 0.1 & 0.039

INcorn36 1.1 3 10 1-May Broadcast 2 0 0.95 0.039

NCcornE16 1.5 1 - 1-Apr T-Band 7 4 1 0.1

NCcornE26 1.5, 1.1 2 60 1-Apr T-Band, 

Broadcast 7 & 2 4 & 0 1 & 0.95 0.1 & 0.039

NCcornE36 1.1 3 10 1-Apr Broadcast 2 0 0.95 0.039

NCcornW16 1.5 1 - 10-Apr T-Band 7 4 1 0.1

NCcornW26 1.5, 1.1 2 60 10-Apr T-Band, 

Broadcast 7 & 2 4 & 0 1 & 0.95 0.1 & 0.039

NCcornW36 1.1 3 10 10-Apr Broadcast 2 0 0.95 0.039

NEcorn16 1.5 1 - 10-May T-Band 7 4 1 0.1

NEcorn26 1.5, 1.1 2 60 10-May T-Band, 

Broadcast 7 & 2 4 & 0 1 & 0.95 0.1 & 0.039

NEcorn36 1.1 3 10 10-May Broadcast 2 0 0.95 0.039

117 Table 6

Watershed scenarios (Georgia and Michigan)

► PRZM-SWAT models (winPRZM for California)

► HUC-14 characterization

► Three stream orders

► 90th centile crop density

► Use of CPY 

► Crop/application schedule resulting in highest exposure predictions from 

sensitivity analysis

► One week application window

► Channel properties from NHD

► Drift 

► Assume % of streams receiving drift = % of crop in watershed

► 1.9% drift for aerial applications (AgDRIFT with 150‟ setback and mediumcoarse droplet) 

► 0.3% drift for ground applications (AgDRIFT with 25‟ setback and fine-medium 

droplet)

► Drift rate = Application rate * total stream surface area * drift factor * PCA

118
8/21/2013

60

Land use distribution of Dry Creek 

watershed, Georgia

48% non-pasture crop

• Cotton 21%

• Peanuts 17%

• Corn 5%

• Pecans 0.6 

Simulations reflected 100% of 

pecans treated

119 Figure 10

Land use distribution of Cedar Creek 

watershed, Michigan 

23% non-pasture crop

• Orchard 12%

• Alfalfa 4.4%

• Corn 3%

Simulations reflected 100% of 

cherries treated

120 Figure 11
8/21/2013

61

Watershed scenario (California)

►California is unique

►Furrow and flood irrigation (winPRZM-SWAT models)

►CPY use is known from PUR database – actual use and 

timing

►8-year simulation

►California-specific runoff-erosion assessment

►CoPST modeling framework

121

Watershed scenario - California

►California unique

►Furrow and flood irrigation 

(winPRZM-SWAT models)

►CPY use is known from PUR 

database

►California-specific runofferosion assessment

►Sacramento River, San Joaquin 

River, and Bay-Delta watersheds

►CoPST modeling framework

►8-year simulation

Orestimba Creek watershed

(SWAT model courtesy of UCD)

Estimated average annual chlorpyrifos loss

122 Figure 9
8/21/2013

62

Land use distribution of Orestimba

Creek watershed, California 

18% non-pasture crop

• Almond 6%

• Alfalfa 4.4%

• Double crop oats/corn 3%

• Corn 2%

• Oats 1.4%

• Tomatoes 1.4%

• Walnuts 1.0% 

Simulations based on actual use 

of CPY

123 Figure 12

Spray drift

X acres were 

treated

but where in the 

square mile grid? 

Conservatively 

assumed all 

acreage near water 

treated.

(Unit of Analysis – PLSS Section)

What were the 

application conditions, 

wind, temperature, etc?

124
8/21/2013

63

Mdrift = Rate × DFRACT × SA x

Area Applied

Area HRU

Where

Mdrift = Drift load (kg) resulting from an application

Rate = Pesticide application rate (kg /ha) for the pesticide

DFRACT = Drift fraction (unitless), based on AgDRIFT calculations for 

chlorpyrifos label for aerial or ground applications, setback distance and 

average stream width.

SA = Total water surface area in subbasin (ha)

AreaApplied is the treated area (ha)

AreaHRU is the subbasin area (ha).

Spray drift

125

Estimated 96-h time-weighted mean 

concentrations of CPY in focus watersheds

126 Table 8

Location 

of 

watershed

Concentration in 

water (μg L-1)

Concentration in 

sediment (μg kg-1)

28-d DT50 96-d DT50 28-d DT50 96-d DT50

California

Minimum 0.003 0.013 4.74 10.8

Median 0.024 0.251 7.91 14.6

90th centilea 1.319 1.543 10.8 20.8

Maximum 1.392 2.142 11.0 22.2

Georgia

Minimum 0.004 0.004 0.007 0.007

Median 0.010 0.010 0.023 0.027

90th centile 0.020 0.020 0.050 0.060

Maximum 0.023 0.023 0.064 0.067

Michigan

Minimum 0.002 0.007 0.027 0.010

Median 0.011 0.018 0.021 0.038

90th centile 0.018 0.034 0.032 0.060

Maximum 0.028 0.043 0.047 0.074

aValues reflect the 90th centile of the annual maxima (1 in 10 y maximum value)
8/21/2013

64

Event duration analysis in focus 

watersheds

127

Location of watershed

Duration of events for 28-d half-life

Georgia Michigan California

Event threshold μg L-1 0.1 1.0 0.1 1.0 0.1 1.0

No. of events 0 0 0 0 10 4

Min. duration (d) n/a n/a n/a n/a 1 1

Max. duration (d) n/a n/a n/a n/a 11 2

Median duration (d) n/a n/a n/a n/a 1 1.5

Avg. duration (d) n/a n/a n/a n/a 2.9 1.5

Duration of events for 96-d half-life

No. of events 0 0 0 3 35 10

Min. duration (d) n/a n/a n/a 1 1 1

Max. duration (d) n/a n/a n/a 1 15 6

Median duration (d) n/a n/a n/a 1 1 1

Avg. duration (d) n/a n/a n/a 1 2.3 1.9

Table 9

Uncertainty

►Uncertainty is inherent in any modeling study due to 

incomplete knowledge, simplifications in representing natural 

systems, and strength of various underlying databases

►Verification of model results was limited for this study 

►Several field-specific runoff studies were simulated (Cryer, 1995; 

McCall, 1984; Poletika, 1994; Racke, 1993)

►Predicted runoff water volume, sediment yield, and chlorpyrifos runoff 

in water and in eroded sediment, were approximately 10-times (±) of 

the measured values without calibration. 

►Estimated environmental concentrations in water in the three 

watersheds were in general agreement with ambient monitoring data 

collected from 2002-2010.

128
8/21/2013

65

Uncertainty (2)

►The characterization of chlorpyrifos in the 

environment could be enhanced

►Addition of a fourth watershed centered around PA corn 

or NE claypan.

►Additional reality in the simulated three watershed (e.g., 

heterogeneity in cropping and soils in Georgia and 

Michigan; management plans being introduced into 

Orestimba Creek, weather-specific drift estimates and 

proximity of fields to water in all three watersheds).

129

The bottom line

►Frequency of detection and concentrations of CPY in 

surface waters across the US have declined since 

(before) 2002.

►Concentrations of CPYO consistently below the LOD, 

even in areas of intensive use.

►Concentrations in water from Tier-3 modeling in GA, MI, 

and CA were similar to the values measured between 

2000-2010.

►Median durations above 0.1 μg/L were ≤ 2 d.

►Paucity of measured values from sediment, only 

modeled values available.

130
8/21/2013

66

Risks to aquatic organisms from 

the use of chlorpyrifos in North 

America

RA 6

131

Sources

Run-off, leaching, 

erosion, tail waters

Upstream 

sources 

(streams)

Spills

Groundwater

Direct application

Drift and 

atmospheric 

deposition

Wildlife 

receptors

Wildlife that 

eat fish/other 

vertebrates

Wildlife that 

eat 

invertebrates 

and plants

Exposures 

(food chain)

Aquatic 

receptors

Fish

Aquatic and 

benthic 

invertebrates

Amphibians/ 

reptiles/ 

mammals

Aquatic 

macrophytes

Aquatic algae/ 

microbiota

Exposures

Bioturbation, Binding 

Phases and

Hydrodynamic 

Factors

Aquatic 

repositories Burial, Resuspension, Sorption and Desorption

Deep 

sediment

Surface 

sediment

Surface 

water & 

wetlands

Exposures

Conceptual model for exposures

Bioconcentration but 

no biomagnification

132

Figure 1
8/21/2013

67

Wildlife 

receptors

Wildlife that 

eat fish/other 

vertebrates

Aquatic 

receptors

Fish

Aquatic and 

benthic 

invertebrates

Amphibians/ 

reptiles/ 

mammals

Aquatic 

macrophytes

Aquatic algae/ 

microbiota

Sources of 

exposure

Deep 

sediment

Surface 

sediment

Surface water 

& wetlands

Direct

Indirect

Wildlife that 

eat aquatic 

plants

Wildlife that 

eat aquatic 

invertebrates

Direct effects 

resulting from 

exposures

Indirect effects 

resulting from 

direct effects

Conceptual models of effects 

133

Figure 2

Cl N

Cl Cl

O P

S

O CH2 CH3

O CH2 CH3

Chlorpyrifos Chlorpyrifos-oxon

[O]

AChE

k OH

1

k3

Phosphorylation k2

AChE

O P

O

O CH2 CH3

O CH2 CH3

AChE

OH

Hydrolysis and 

reactivation

Cl N

Cl Cl

O P

O

O CH2 CH3

O CH2 CH3

AChE

O P

O

OH

O CH2 CH3

k-1

Aging (hydrolysis)

Aged enzyme cannot 

be reactivated

Recovered enzyme 

returns to normal 

function

Cl N

Cl Cl

OH

TCP

+

Mechanism of action - recovery

134
8/21/2013

68

Recovery – addressing k3

Exposure and response

Time

Response to 

exposure 1

Response to 

exposure 2

135

Recovery

Exposure and response

Time

Response to 

exposure 1

Response to 

exposure 2 

partially additive 

to exposure 1

136
8/21/2013

69

Recovery

Taxon Recovery time

Crustacea and insects 1-7 d

Fish 4-8 wks

137

►Hydraulics of flowing water – pulsed exposures.

►Reciprocal relationship between time of 

exposure and effects.

►Recovery of AChE via k3

►Synthesis of new AChE

►Data for invertebrates and fish

►Aquatic organisms can also recover via 

propagules, metapopulations, and/or migration DOW CONFIDENTIAL - Do not share 

without permission

Selection of toxicity data

Strength of 

methods

1 2 3 4 5

Description of 

the 

experimental 

and procedures

Inadequately 

described or 

incorrect

Critical 

information on 

methods 

missing

Critical 

information on 

methods and 

procedures 

provided

Procedures 

described so 

that the study 

could be 

replicated or 

spirit of GLP

Guideline study 

or complete 

detailed 

protocol or full 

GLP

QA/QC None Some QC (e.g., 

exposures 

measured 

once)

More QC (e.g., 

exposures 

measured on a 

regular basis)

Robust QA/QC Full QA/QC

Transparency 

of data

Critical data not 

provided

Summary data 

only

Summary data 

with variance 

character-ized

Key raw data 

provided

All raw data 

provided

Concen-trat-ion

s tested

Only 1 conc. 

tested

2 concs. tested 3 concs. Tested 

or field study > 

3 sites

4 concs. tested ≥ 5 concs. 

tested

Descriptors 

from Klimisch

et al. 1997

Not assignable Not reliable With restriction Without restrictions

Klimisch H-J, Andreae M, Tillmann U. 1997. A systematic approach for evaluating the quality of 

experimental toxicological and ecotoxicological data. Regulatory Toxicology and Pharmacology

25:1-5.

138

Table 1
8/21/2013

70

Toxicity data - duration

►Previous review (Giesy et al. 1999) used 2-d 

toxicity data.

►Current review used standard 48 to 96-h LC50 

tests as a conservative measure of sensitivity.

►Other responses, such as behavioral not 

included – unable to link to the apical responses.

►Chronic toxicity not included – all exposures are 

short and chronic exposures assessed in cosms.

►Data characterized as Species Sensitivity 

Distributions (SSDs) using SSD-Master Ver 2 

(2007).

139

Toxicity data - algae

►Not expected to be very sensitive.

►There were 6 species of plants tested, one 

met the criteria for inclusion.

►Range of EC50s for algae was from 138 

to 2000 μg L

-1

►Not considered further.

140
8/21/2013

71

Crustaceans

Insects

Fish

0.0

0.2

0.4

0.6

0.8

1.0

0.001 0.1 10 1000 100000 10000000 1E+09 1E+11 Proportion of taxa affected

Concentration (ng L-1)

Normal

Logistic

Gompertz

Weibull

Fisher-Tippett

0.0

0.2

0.4

0.6

0.8

1.0

0.001 0.1 10 1000 100000 10000000 Proportion of taxa affected

Concentration (ng L-1)

Normal

Logistic

Gompertz

Weibull

Fisher-Tippett

0.0

0.2

0.4

0.6

0.8

1.0

0.001 0.1 10 1000 100000 10000000 1E+09 Proportion of taxa affected

Concentration (ng L-1)

Normal

Logistic

Gompertz

Weibull

Fisher-Tippett

SI Figure 1

Toxicity data – crustaceans (23)

142

Concentration of chlorpyrifos (μg L-1)

10-3 10-2 10-1 100 101 102 103 104

Proportion of crustacean species

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Simocephalus vetulus

Daphnia magna

Gammarus palustris

Procambarus sp

Amphiascus tenuiremis

Gammarus fossarum

Orconectes immunis

Asellus aquaticus

Eriocheir sinensis

Neocaridina denticulata

Daphnia ambigua

Ceriodaphnia dubia

Hyalella azteca

Moina australiensis

Gammarus lacustris

Paratya australiensis

Palaemonetes pugio

Neomysis integer

Daphnia pulex

Daphnia carinata

Daphnia longispina

Gammarus pulex

Macrobrachium rosenbergii

5

th centile = 

0.038 μg L-1

L 95%CI

U 95%CI

Figure 1
8/21/2013

72

Toxicity data - crustaceans

►Twenty-three studies met the criteria for 

inclusion.

►Range of LC50s was 0.035 to 457 μg 

CPY L

-1

►HC5 (95%CI) was 0.038 (0.024-0.062) μg 

CPY L

-1

.

143

Toxicity data – insects (18)

144 Concentration of chlorpyrifos (μg L-1

)

10-3 10-2 10-1 100 101 102 103 104

Proportion of insect species

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Deleatidium sp.

5

th centile = 

0.091 μg L-1

Notonecta maculata

Chironomus riparius

Atalophlebia australis

Simulium vittatum

Chaoborus obscuripes

Chironomus dilutus

Anax imperator

Plea minutissima

Corixa punctata

Sigara arguta

Cloeon dipterum

Ranatra linearis

Xanthocnemis zealandica

Paraponyx stratiotata

L 95%CI

U 95%CI

Figure 4
8/21/2013

73

Toxicity data - insects

►Eighteen studies met the criteria for 

inclusion.

►Range of LC50s was 0.05 to >300 μg 

CPY L-1

►HC5 (95%CI) was 0.091 (0.024-0.062) μg 

CPY L

-1

.

145

Toxicity data – fish (25)

146 Concentration of chlorpyrifos (μg L-1

)

10-3 10-2 10-1 100 101 102 103 104

Proportion of fish species

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Menidia menidia

Menidia peninsulae

Leuresthes tenuis

Lepomis macrochirus

Fundulus heteroclitus

Pungitius pungitius

Atherinops affinis

Menidia beryllina

Poecilia reticulata

Cyprinus carpio

Oncorhynchus mykiss

Gasterosteus aculeatus

Oncorhynchus clarki

Sander vitreus

Melanotaenia fluviatilis

Salvelinus namaycush

Pimephales promelas

Oryzias latipes

Gambusia affinis

Opsanus beta

5

th centile = 

0.820 μg L-1

Aphanius iberus

L 95%CI Rutilus rutilus

U 95%CI

Leuciscus idus

Figure 5
8/21/2013

74

Toxicity data - fish

►Twenty-five studies met the criteria for 

inclusion.

►Range of LC50s was 0.53 to 806 μg CPY 

L

-1

►HC5 (95%CI) was 0.820 (0.494-1.360) μg 

CPY L

-1

.

147

Other groups

►Amphibians

►Three studies met the criteria for inclusion 

and one was questionable.

►Range of LC50s was 14 to a questionable 

value of 5,174 μg CPY L

-1

. 

►Not included in the ERA – fish are protective.

►Other invertebrates

►Rotifers, mollusks, worms.

►All EC50s > 287 μg CPY L

-1

, not included in 

ERA

148
8/21/2013

75

Toxicity to benthos

LC50 of CPY

Species μg CPY Kg-1(dw) ng g-1 OC

H. azteca (10 d) 399 2,122

C. dilutus (10 d) 399 4,815

149

►Concentration in pore water close to water-only 

LC50.

►Risk extrapolated from the water-column 

organisms as in Giesy at al. (1999).

Table 3

Toxicity CPYO

LC50 (μg L-1)

Species CPY CPYO

D. magna (48 h) 0.82 1.9

L. macrochirus (96 h) 4.2 1.1

150

►One value for Rana boylii > 5 μg L-1from a 

study that did not meet the criteria for inclusion.

►ERA for CPYO strongly correlated to parent.

►Formed in vivo and in the environment.

►Implicitly included in toxicity testing, more polar, more 

reactive in water.

►Not found in surface waters above LOD, 

separate ERA not needed.

Table 4
8/21/2013

76

151

►Since the 1999 review of CPY,

►Four new studies have been published.

►Also, the 1993 Springborn study has been reanalyzed 

using Principal Response Curves.

►Almost without exception, all of the cosm studies 

have demonstrated an ecosystem-level No 

Observed Adverse Effect Concentration 

(NOAECeco) of 0.1 μg/L.

►Responses of populations to chlorpyrifos in cosms 

very consistent with laboratory tests.

►Crustaceans > insects > fish > rotifers

Effects in cosms

152
8/21/2013

77

Risks from measured exposures

153

Concentration of chlorpyrifos (μg L-1)

10-3 10-2 10-1 100 101 102 103 104

Proportion of species

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

USGS, 0.056 pre-2001

USGS, 0.008 post-2001

USGS – max 95th

centiles from 

measured 

concentrations

Cosm NOAECeco

Figure 6

Risks from modeled exposures (CA)

154

Percent of species with exceedences of 96-h LC50s

0 20 40 60 80 100

Percent exceedences of 96-h LC50s, 

Orestimba Creek, CA

0

20

40

60

80

100

Fish

Crustacea

Insects

Figure 7
8/21/2013

78

Risks from modeled exposures (MI)

155

Percent of species with exceedences of 96-h LC50s

0 20 40 60 80 100

Percent exceedences of 96-h LC50s, 

Cedar Creek, MI

0

20

40

60

80

100

Fish

Crustacea

Insects

Figure 8

Risks for benthos modeled 

exposures

►None of the maximum modeled 

concentrations exceed the toxicity value 

for sediments

156

μg CPY Kg-1

Species LC50 GA MI CA

H. azteca (10 d) 399 0.08 0.09 22.8

C. dilutus (10 d) 399
8/21/2013

79

RADAR

Time

Threshold (HC5)

Peak Height

Duration

Date

Data

Date

Concentration

Recovery time

157

Radar analysis of pulsed exposures 

Taxon Threshold 

Conc. (μg L-1)

Duration 

(h)

Recovery 

period (d)

Crustacea > 0.038 = 96 ≤ 14

Insects > 0.091 = 96 ≤ 14

Fish > 0.802 = 96 ≤ 56

158

Taxon Number of peaks exceeding all 3 thresholds

Georgia

1961-1990

Michigan

1961-1990

California OC

2000-2009

Crustacea 0 0 4

Insects 0 0 3

Fish 0 0 2

Table 6

Table 7
8/21/2013

80

The bottom line

►Risks from CPY across the USGS monitoring sites have 

declined since 2000

►Risks from CPYO in surface waters are de minimis.

►For CPY, the HC5 concentrations and the NOAECs for 

the cosms were similar to the previous assessment.

►De minimis risks to benthos from CPY.

►More data were available to characterize recovery from 

inhibition of AChE.

►Pulsed exposures not at in issue in GA and MI but a 

potential issue in Orestimba Creek in CA.

►Few incidents reported and all were related to misuse, 

misapplication, or deliberate dumping.

159

Risk to pollinators from the use of 

chlorpyrifos in North America

RA 7

160
8/21/2013

81

Importance of pollinators

►More than 3⁄4 of angiosperms rely on animals for 

pollination

►Ca. 75% of global fruit, vegetable and seed crops 

depend on animal pollination to some extent

►Keystone species  Pollination lays a 

groundwork for essential ecosystem services

►Seed development  continued evolution and 

maintenance of floral biodiversity

►Declines in populations of pollinator are of 

concern

►Reports of insecticides, including CPY causing 

effects on pollinators

161

Bee pollinators

►Bees by far the most important 

animal pollinators

►Agricultural pollination relies on wild 

and managed bees

►European honey bee, Apis mellifera

►The workhorse

►Generalist pollinator found worldwide

►Worth ~ $15 billion to agriculture in the 

United States 

►Critically important for almonds, apples 

and other tree fruits, blueberries and 

other berries, alfalfa seed, melons, 

sunflowers, etc. 162
8/21/2013

82

Honey bee biology and RA

►Considerations for risk assessment

►„Superorganism‟ – colony growth and survival 

depends on the collective actions of different castes

►Different castes of bees have different functions, 

which can result in differential exposure in terms of 

duration, magnitude, and mode 

►Colonies typically have a 10-30% reserve of workers

►Reflects and accommodates high turnover rate 

►Survival of an individual bee may be of little consequence

►Large forage area of honey bees complicates the 

task of estimating and avoiding potential exposure

163

Bee pollinators

►Bumble bees (Bombus spp.)

►A smaller „super-organism‟

►Maintenance of natural floral 

diversity and agricultural pollination

►Ground nesters (e.g. rodent holes) 

but also commercially produced 

►Recently utilized as vectors of 

biopesticides

164
8/21/2013

83

Bee Pollinators

►Leafcutter and mason bees

►E.g., Megachile rotundata, 

Osmia lignaria

►Wild but also accept trapnests and so are easily 

managed and produced 

►Alfalfa leafcutter bee can be 

deployed in great numbers 

 alternative to honeybees 

on some crops

165

Biology of solitary bees and ERA

►Most non-Apis bees are significantly smaller than 

honey bees  relatively higher dose

►Eggs mostly laid directly on raw pollen and nectar 

 often greater concentrations of pesticide

►Forage over smaller area  less „dilution‟ of 

pesticide

►Individuals in the field are 

relatively more important

►Different nest materials (e.g., mud, 

leaf pieces) and sites (e.g., ground,

stems)

166
8/21/2013

84

Other pollinators

►“Pollinator” = any vector that moves 

pollen from the male anthers of a 

flower to the female stigma of a flower 

- excluded 

167

The problem

►Chlorpyrifos is toxic to insect pollinators

►Agroecosystem in which chlorpyrifos is used 

contains managed and wild pollinators

►Almonds, citrus fruits, berries; pollinators are key 

►E.g., corn 

• Potentially large inputs of chlorpyrifos

• Wind pollinated but may be an important source of 

pollen for multiple species of pollinators

►In addition to pollen and/or nectar, pollinators may 

obtain nesting materials and occupy nesting sites in 

habitats subject to chlorpyrifos exposure 

168
8/21/2013

85

Problem formulation and 

conceptual model

►Recognized the protective warnings for pollinators 

on the labels.

►Focus on formulations currently used in agriculture 

in the US.

►Lorsban® 4E

►Lorsban Advanced®

►Lorsban 15G

►Conceptual model based on SETAC Pellston (2011) 

and new US EPA (2012) proposals.

169

CPY AND CPYO FROM GROUND/AERIAL SPRAY IN 

AGRICULTURAL USE 

CPY ON 

POLLINATOR

S T R E S S O R

PRIMARY 

COMPARTMENTS/ 

ROUTES OF 

EXPOSURE

PRIMARY 

EXPOSURE 

TYPE

DIRECT 

DEPOSITION 

& AERIAL 

DRIFT

TRANSFORMATION IN ALL 

MATRICES

- DETOXIFICATION

- FORMATION OF CPYO IN AIR

INHALATION 

TOXICITY

CPY OR CPYO SUBLETHAL 

BODY BURDEN 

TRANSPORTED TO HIVE 

OR PROGENY 

HIVE PRODUCTS (Honey, 

Bee Bread, Royal Jelly), Wax

CPY IN POLLEN CARRIED 

TO HIVE OR FOR LARVAL 

FOOD

CPY ON 

VEGETATION 

CPY IN AIR 

vapor, dust/aerosol

CPYO formation

CPY ON SOIL

CPY IN SURFACE 

WATER

CPY, CPYO IN 

RAIN WATER & 

DEW ON 

SURFACES

& IN POOLS

CONTACT TOXICITY

BODY & TARSAL

ORAL TOXICITY

CPY, CPYO 

RECONCENTRATION 

IN WAX (In hive)

SECONDARY 

MOVEMENT & 

TRANSFORMATION

Grooming

R E C E P T O R SOCIAL and SOLITARY POLLINATOR PROTECTION GOALS

S E C O N D A R Y & D E L A Y E D O R A L 

T O X I C I T Y T O H I V E B E E S , Q U E E N , 

D R O N E S , P R O G E N Y ( B r o o d )

CPY ON PREY

CPY IN 

GROUNDWATER

POLLEN

NECTAR 

FOLIAGE &

BUD WAX Leaf cutting,

propolis

SECONDARY 

EXPOSURE 

TYPE

White box with dashed frame = Incomplete pathway

Dashed arrow = may be insignificant for CPY, CPYO.

ORAL & CONTACT 

TOXICITY

PRIMARY & SECONDARY 

EXPOSURE FROM SOIL 

(e.g. Andrenidae Osmia, 

Peponapis, Halictid)

CPY OR CPYO CARRIED 

ON LEAF CUTTINGS USED 

FOR HOUSING (Megachilid)

 

GUTTATION

HONEYDEW 

Figure 1 170
8/21/2013

86

Proposed protection goals

from Fischer and Moriarty 2011

CPY ERA

focus on hive

171

Potential exposures of 

pollinators to CPY

►Formulations currently used in U.S. are 

used on alfalfa, corn, cotton, soybean, 

sunflower, tree nuts (e.g., almond, pecan, 

walnut)

►At least partially dependent upon pollinators, 

or are utilized as forage or nesting material for 

pollinators

172
8/21/2013

87

Direct exposure to sprays

►End-user labels for products formulated with 

CPY state that CPY is highly toxic to bees 

exposed to direct treatment or residues on 

blooming crops or weeds, and that the product is 

not to be applied or allowed to drift to blooming 

crops or weeds if bees are visiting the treatment 

area.

►Worst case and forage radius of honey bees 

assume this will still occur to some extent

173

Characterization of exposure

Life stage Minimum dose (μg 

CPY bee-1)

Maximum dose (μg 

CPY bee-1)

Adult 7.5 – 61 30.5 – 183

Larvae 3.1 – 25 12.6 – 75

Tier-1 estimates of CPY dietary exposure in honey bees 

(aggregate nectar/honey and pollen consumption) during 

foliar applications of Lorsban 4E or Lorsban Advanced at 

minimum and maximum application rates based on T-REX 

estimates of concentrations in pollen and nectar.

174

Not the best model for bees!

Table 1
8/21/2013

88

Pollen and honey

Matrix Concentration (μg kg-1) % of 

samples 

Mean Median Maximum 95th centile LOD

Pollen 53 4.4 830 227 0.1 44 (153/350)

35 --- 35 --- 10.0 0.5 (1/198)

955 --- --- --- 0.1 100 (2/2)

Honey 46 --- 80 --- 4.0 42 (13/31)

--- --- 15 --- 0.8 ---

ND --- ND 3.5 0 (0/239)

ND ND ND 5.0 0 (0/51)

Measured concentrations of CPY detected in pollen and 

honey from honey bee hives

Table 2 175

Exposures

Life stage 

(consumption)

Median dose (μg CPY 

bee-1)

95th centile dose (μg CPY 

bee-1)

Adult (292 mg) 1.28 x 10-3 6.61 x 10-2

Larva (120 mg) 5.26 x 10-4 2.72 x 10-2

Tier-2 estimates of CPY exposure through daily consumption 

of pollen and nectar by adult and larval honey bees. Based on 

values measured in diet.

Table 3 176

Also characterized exposures via residues on leaf (Table 4), 

beeswax (Table 5, may be a sink), soil (non-Apis bees), dew 

and puddles (Table 13)
8/21/2013

89

Exposures

Plant Time (d) Residue (μg cm-2

) 

adjusted to 1.12 kg ha-1

Cotton 0 3.64

1 0.13

2 0.071

3 0.055

4 0.034

Tier-2 Dissipation and concentration of dislodgeable foliar 

residues.

Geometric means concentrations at 0 and 3-4 days after 

spraying were 1.46 and 0.019 μg cm-2(adjusted for a 1.12 

kg/ha application rate)

Table 4 177

Exposures

Matrix Mean Median Maximum 95th 

centile

Comb 

beeswax 24.5 4.3 890.0 55.7

14.9 --- 19.0 ---

172 --- --- ---

8 --- 15 ---

NDd ND ND ---

Foundation 

beeswax 22.2 10.0 110.0 76.4

Tier-2 Concentrations of CPY detected comb and foundation 

beeswax from honey bee hives.

Wax may be a sink for CPY and reduces exposures

178

Table 5
8/21/2013

90

Exposures via soil and puddles

►No data for soil – more relevant to non-apis

bees.

►Puddles (intake = 47 μL d-1)

►Tier-1 rice model based on Koc and direct overspray:

►2.40 x 10-7 μg CPY bee-1 d

-1

►Tier-2 PRZM/EXAMS:

► 95th centile maximum daily dose 0.027 μg bee-1 d

-1

►Water carrying; 0.71 μg bee-1 d

-1

PRZM/EXAMS based on large storm events, most years 

values were zero. Bees do not forage during large storm 

events – no exposure?

Table 13 179

Exposures via dew, air and wax

►Dew Intake = 47 μL d-1

►Tier-1 Koc method

► 0.034 μg CPY bee-1 d

-1

►Tier-2 LiquiPARAM

►95th centile maximum daily dose 0.0099 μg bee-1 d

-1

►Water carrying; 0.05 μg bee-1 d

-1

►Air

►CPY not used as a fumigant insecticide, exposure 

below threshold of toxicity for bees.

►Wax

►No effects when exposed to contaminated comb

180
8/21/2013

91

Measures of effects

►Measured acutely (< 96 h) through

dermal contact and oral tests

►Chronic tests can use the same exposure methods 

and can be done on adult bees for 10-14 days. 

►Mortality, knockdown (i.e., live but immobile), staggering 

(poorly coordinated movements) and responsiveness 

(hypo- or hyper-responsive) 

►Sublethal endpoints: learning, 

behavior, physiology, impaired 

growth, reproduction and survival

181

Topical toxicity (acute)

Formulation % Purity Topical LD50 

(μg CPY bee-1)

Technical ≥ 95 0.059

Technical 99% 0.115

Technical product geometric mean 0.082

Lorsban 48E 48 0.024

Dursban F 97.4 0.070

Lorsban Advanced 41.1 0.14

Dursban 480 48 0.22

Dursban WG 75 0.54

Formulated product geometric mean 0.123

182 Table 6
8/21/2013

92

Oral toxicity (acute)

Formulation % Purity Topical LD50 

(μg CPY bee-1)

Technical ≥ 95% 0.114

Lorsban 4E --- 0.11

Dursban 4 48 0.29

Dursban 480 48 0.33

Dursban F 97.4 0.36

Lorsban Advanced 41.1 0.39

Lorsban 50WP 50 0.4

Lorsban 50W 50.2 0.46

Dursban WG 75 1.1

Formulated product geometric mean 0.36

183 Table 7

Field studies

►Effects on Bombus impatiens observed after 14 

d exposure via treated turf

►Despite short-term lethal effects on honey bees 

observed in field studies;

►Colonies should be able to survive such exposure 

with few long-term effects

►Risk reduced or eliminated if application is not made 

when flowers are open.

►Non-Apis pollinators with females that annually 

establish nests, which are much smaller than that of 

the honey bee, are likely more sensitive to CPY 

exposure.

184
8/21/2013

93

Incident data

185 Table 11

Crop Reported CPY incidents with honey 

bees

1990-1999 2000-2009 2010-present

TOTALS 26 4 1

Reporting of incidents is poor and critical data are frequently omitted.

Tier-2 risk quotients, oral pollen

Variable

Larvae (120 mg) Adults (292 mg)

Median 95th 

centile Median 95thcentile

Dose (μg 

CPY bee-1)

5.26 x 10-4 2.72 x 10-2 1.28 x 10-3 6.61 x 10-2

LD50 0.146 0.146 0.114 0.114

RQ 0.004 0.19 0.011 0.580

186 Table 12
8/21/2013

94

Risk quotients, oral water

Variable Median 95th centile or maximum

OCSPP 

2012 

dew/wet 

foliage

Dew/wet 

foliage

LiquiPARAM

Tier-1 rice 

model 

puddlea

PRZM/ 

EXAMS 

puddle/pore 

water

OCSPP 

2012 

dew/wet 

foliage

Dew/wet 

foliage

LiquiPARAM

PEC at 1.12 kg 

CPY/ha (μg L-1)

140 102 5.10 x 10-3 571 730 210

Dose from 

drinking

water(μg bee-1)

0.007 0.005 2.40 x 10-7 0.027 0.034 0.010

Tier 1 RQ

drinking water

0.06 0.04 2.10 x 

10-6

0.24 0.30 0.09

Dose based on 

water collected 

(μg bee-1)

0.035 0.03 6.38 x 10-6 0.71 0.18 0.05

RQ for water 

collection by 

honey bees

0.31 0.22 5.59 x 

10-5

6.26 1.60 0.46

187 Table 13

PRZM/EXAMS upper centiles from large storm events after 

application; bees will not forage under these conditions.

Risks estimated from field tests

►Foliage treated with CPY at the label rate can 

remain lethal to honey bees, alfalfa leaf cutting 

bees, and alkali bees for several days after 

application.

►Some mortality may occur 1-2 d after application 

on flowering crops

►Reduced foraging may persist for up to a week

►Residues remaining after 7 d have no impact

►Rapid, normal turnover of foragers in hives 

(resiliency) and availability of alternate foraging 

sites should buffer out these short-term effects.

188
8/21/2013

95

Risks from contaminated soil

►No data for ground-nesting bees

►Availability of residues reduced by adsorption to 

soils.

►Architecture of the nest may reduce exposures.

189

The bottom line

►CPY is toxic by direct contact but this is 

mitigated by label restrictions

►Reported incidents of bee kills are rare, especially 

after 2000.

►Most important route of exposure other than 

direct is via:

►Nectar

►Pollen

►Little risk with Tier-2 assessment

►Negligible risks

►Water

►Propolis and wax

190
8/21/2013

96

Thank You!!!!! Questions????

191

John P. Giesy, Ph.D., FRSC

Professor & Canada Research Chair in Environmental Toxicology

Dept. Veterinary Biomedical Sciences & Toxicology Centre

University of Saskatchewan

Saskatoon, SK, Canada

Tel: (306) 966-2096 Fax: (306) 931-1664

Email: John.Giesy@usask.ca

Web Site: http://ww.usask.ca/toxicology/faculty_profiles/giesy_john.html

Keith Solomon, Ph.D., Fellow ATS, Prof. Emeritus (UofG)

Centre for Toxicology, School of Environmental Sciences

University of Guelph,

Guelph, ON, N1G 2W1, Canada

Tel: +1-519-824-4120 x 58792 Fax: +519-837-0442

ksolomon@uoguelph.ca 

192