Department of Pesticide Regulation 

Mary-Ann Warmerdam 

Director M E M O R A N D U M Arnold Schwarzenegger 

Governor 

1001 I Street • P.O. Box 4015 • Sacramento, California 95812-4015 • www.cdpr.ca.gov

A Department of the California Environmental Protection Agency 

 Printed on recycled paper, 100% post-consumer--processed chlorine-free. 

TO: John S. Sanders, Ph.D. 

 Environmental Program Manager II 

 Environmental Monitoring Branch 

FROM: Mark Pepple 

 Staff Environmental Scientist 

 Environmental Monitoring Branch 

 916-324-4086 

DATE: May 29, 2009 

SUBJECT: PROCEDURE FOR IDENTIFYING PESTICIDES WITH A HIGH POTENTIAL 

TO CONTAMINATE SURFACE WATER 

This memorandum explains how the pesticides that may be regulated to prevent surface water 

contamination were identified. 

Environmental Monitoring staff are developing regulations to protect surface water from 

pesticides. The regulations will list pesticides that have a high potential to contaminate surface 

water and then specify mitigation measures designed to protect beneficial uses of waters of the 

state from those pesticides. 

We identified pesticides that have a high potential to contaminated surface water by first listing 

all pesticides detected in surface water or sediment from the Department of Pesticide 

Regulation’s (DPR’s) Surface Water Database at 

<http://www.cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm>. The database contains sampling 

results from 1991 to the present. To that list we added fipronil and pyrethrins, which are draft 

detections pending completion of the monitoring reports (Table 1). For screening purposes, we 

also added all active ingredient isomers of pesticides detected, and the associated salts, esters, 

and/or amines of 2,4-D, dicamba, glyphosate, and MCPA (Table 2). 

The following five pesticides were removed from the list because they had single detections 

(number of samples analyzed in parentheses): bromoxynil octanoate (193), fenamiphos (635), 

hydramethylnon (203), paraquat dichloride (312), and tetrachlorvinphos (1243). Five additional 

pesticides were removed from the list for the stated reasons: endosulfan because it is already 

subject to California-only label requirements to protect surface water; molinate because its use 

will no longer be allowed after August 2009; pyrethrins because they have very short half-lives; 

terbuthylazine because all of its uses would qualify for the provision that would exempt all 

intentional applications to water in accordance with all regulatory requirements; and thiobencarb 

because it is being addressed by the rice industry and the Central Valley Regional Water Quality 

Control Board in a different forum to protect surface water. 
John S. Sanders, Ph.D. 

May 29, 2009 

Page 2 

Finally, the list was screened to exclude pesticides that are detected in surface water at levels that 

are relatively low compared to the levels that cause aquatic toxicity or that are protective of 

human health in drinking water. This screening process was not used to remove any pesticides 

remaining on the list that were detected exclusively in sediment. The U.S. Environmental 

Protection Agency (EPA) Aquatic Life Benchmark Table, as of November 2008, 

http://www.epa.gov/oppefed1/ecorisk_ders/aquatic_life_benchmark.htm> was used to obtain the 

lowest aquatic life benchmark for pesticides on the DPR draft list. It should be noted that EPA is 

in the process of revising the aquatic life benchmarks so values in Table 2, as of November 2008, 

may be different from those in the current EPA Aquatic Life Benchmark Table. For pesticides 

with no aquatic life benchmark, the U.S. EPA Office of Pesticide Programs Pesticide Ecotoxicity 

Database <http://www.ipmcenters.org/Ecotox/index.cfm>, as of November 2008, was used to 

obtain the lowest acute LC50 or EC50, or the lowest chronic no observable effect level (NOEL) 

for the standard test species that U.S. EPA uses to assess pesticide aquatic toxicity. For acute 

toxicity to freshwater fish, the standard test species is usually rainbow trout or bluegill sunfish; 

for chronic toxicity to freshwater fish, rainbow trout or fathead minnow; for acute and chronic 

toxicity to freshwater invertebrates, midge, scud (amphipods), or daphnids; for acute toxicity to 

freshwater nonvascular plants, green algae or diatoms; and for acute toxicity to freshwater 

vascular plants, duckweed. To be consistent with the methodology used to establish aquatic life 

benchmarks, the lowest toxicity values were multiplied by the appropriate levels of concern 

(LOC) factors (LOC=1 for chronic fish and invertebrate values, and for acute vascular and 

nonvascular plant values; LOC=0.5 for acute fish and invertebrate values). 

In addition, the Department of Fish and Game has completed hazard assessments for 17 of the 71 

pesticides detected in surface water and reviewed by DPR for their potential to contaminate 

surface water. The lowest values to protect human health or aquatic organisms used in the DPR 

screening in Table 2 were compared with the lowest values to protect aquatic organisms 

developed in the DFG hazard assessments. Only toxicity values measured on the active 

ingredient were used unless there were only data for formulated products. We computed the 

ratio of the lowest DFG value to the lowest DPR value. Ratios of less than one indicate that 

DPR values were less protective of aquatic organisms than the DFG values. The ratios ranged 

from 0.03 for cypermethrin to 173,000 for 2,4-D. The median ratio was 6.2. Although the DFG 

values were lower for carbofuran, chlorpyrifos, cypermethrin, S-cypermethrin, diazinon, 

methidathion, methomyl, and methyl parathion, they did not result in any change in the list of 

pesticides identified as having a high potential to contaminate surface water. 

For drinking water health protective levels, the California Central Valley Regional Water Quality 

Control Board’s Compilation of Water Quality Goals at 

<http://www.swrcb.ca.gov/rwqcb5/water_issues/water_quality_standards_limits/water_quality_g

oals/wq_goals_2008.pdf>, as of November 2008, were used to identify, for each pesticide, either 

a California Department of Public Health (CDPH) or U.S. EPA maximum contaminant level 

(MCL), or, if an MCL is not established, the lowest drinking water concentration level for 
John S. Sanders, Ph.D. 

May 29, 2009 

Page 3 

protection of human health of one of the following levels: a U.S. EPA Integrated Risk 

Information System reference dose as a drinking water level, a drinking water health advisory 

(HA) or suggested no-adverse-response level for toxicity other than cancer risk, or various 

measures of one-in-a-million incremental cancer risk estimates for drinking water, as footnoted 

in the table below. 

If the lowest of the aquatic life benchmark or acute or chronic aquatic toxicity value, or human 

health protection level, was 50 parts per billion (ppb) or above (five times or greater than the ten 

ppb 95th percentile of detected water concentrations in the DPR’s Surface Water Database), the 

pesticide was excluded from the draft DPR list. The following pesticides were excluded because 

their aquatic toxicity or level to protect human health is 50 ppb or higher: 2,4-D and related 

pesticides, butylate, chlorthal dimethyl, cycloate, EPTC, glyphosate and related compounds, 

metalaxyl, napropamide, oxamyl, prometon, propiconazole, tebuthiuron, triclopyr butoxy ethyl 

ester, and triclopyr triethylamine salt. 
John S. Sanders, Ph.D. 

May 29, 2009 

Page 4 

A summary of these data for the pesticides screened for determining potential to contaminate 

surface water is shown in Table 2. 

Table 1. Pesticides detected in surface water or sediment 

chemical DPR chem code 

2,4-D 636 

alachlor 678 

aldicarb 575 

atrazine 45 

azinphos-methyl 314 

benefin 53 

bentazon, sodium salt 1944 

bifenthrin 2300 

bromacil 83 

bromoxynil octanoate 834 

butylate 565 

carbaryl 105 

carbofuran 106 

chlorpyrifos 253 

chlorthal-dimethyl 179 synonym: dacthal and DCPA

cycloate 516 

cyfluthrin 2223 

cypermethrin 2171 

DDVP 187 synonym: dichlorvos 

deltamethrin 3010 

diazinon 198 

dicamba 200 

dicofol 346 

dimethoate 216 

disulfoton 230 

diuron 231 

endosulfan 259 

EPTC 264 synonym: eptam 

esfenvalerate 2321 

ethalfluralin 2166 

ethoprop 404 

fenamiphos 1857 

fenoxycarb 2283 
John S. Sanders, Ph.D. 

May 29, 2009 

Page 5 

chemical DPR chem code 

fenpropathrin Initially omitted 

fipronil 3995 

glyphosate 2997 

hexazinone 1871 

hydramethylnon 2203 

imidacloprid 3849 

lambda cyhalothrin 2297 

linuron 361 

malathion 367 

MCPA 2326 

MCPA, dimethylamine salt 786 

metalaxyl 2132 

methidathion 1689 

methiocarb 375 

methomyl 383 

methyl isothiocyanate 392 

methyl parathion 394 

metolachlor 1996 

metribuzin 1692 

molinate 449 

napropamide 1728 

norflurazon 2019 

oryzalin 1868 

oxadiazon 2017 

oxamyl 1910 

oxyfluorfen 1973 

paraquat dichloride 1601 

pendimethalin 1929 

permethrin 2008 

phorate 478 

phosmet 335 

prodiamine 2236 

prometon 499 

prometryn 502 

propanil 503 

propargite 445 

propiconazole 2276 

propoxur 62 
John S. Sanders, Ph.D. 

May 29, 2009 

Page 6 

chemical DPR chem code 

propyzamide 694 

pyrethrins 510 

pyriproxyfen 4019 

S.S.S-tributyl phosphorotrithioate 190 synonym: tribufos 

siduron 603 

simazine 531 

tebuthiuron 1810 

terbuthylazine 3004 

tetrachlorvinphos 305 

thiobencarb 1933 

triallate 49 

triclopyr 2131 

trifluralin 597 
John S. Sanders, Ph.D. 

May 29, 2009 Page 7 Table 2. Pesticides detected in surface water (and related chemicals) screened for possible regulation to protect s

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

2,4-D and related 

pesticides 70a 1.124B x 0.5 = 0.56 Daphnia magna Acute invertebrates 0.56 

Alachlor 2a 1.64A Acute nonvascular plants 1.64 Aldicarb 3b 0.46A Chronic fish 0.46 

Atrazine 1c 1A Acute nonvascular plants 1 

Azinphosmethyl 87.5d .036A Chronic invertebrates .036 

Benefin

(benfluralin) 700d 1.9A Chronic fish 1.9 
John S. Sanders, Ph.D. 

May 29, 2009 Page 8 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Bentazon, sodium 

salt 18c 4500A Acute nonvascular plants 18 

beta-Cyfluthrin NA .007B (Cyfluthrin NOEL) x 1 = .007 Daphnia magna/ Chronic invertebrates 0.007 

Bifenthrin 110e 0.0013B (NOEL) x 1 = .0013 Daphnia magna/ Chronic invertebrates 0.0013 

Bromacil 70f 6.8A 

Selenastrum capricornutum/ 

Acute nonvascular plants Acute nonvascular plants 

6.8 

Bromoxynil 

octanoate1 140e 2.5A (bromoxynil) Chronic invertebrates 2.5 

Butylate 350e 105A Acute fish 105 
John S. Sanders, Ph.D. 

May 29, 2009 Page 9 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Carbaryl 40g 0.5A Chronic invertebrate 0.5 

Carbofuran 18c 0.75A Chronic invertebrate 0.75 

Chlorpyrifos 2f .04A Chronic invertebrate 0.04 

Chlorthal dimethyl 70e 11000A Acute vascular and nonvascular plants 70 

Cycloate NA 1300A Acute invertebrates 1300 

Cyfluthrin NA 0.004B (NOEL) x 1 = .004 Daphnia magna/ Chronic invertebrates 0.004 
John S. Sanders, Ph.D. 

May 29, 2009 Page 10 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Cypermthrin, ciscypermethrin 70e .069A Chronic invertebrates .069 

S-cypermethrin 70fe Assume same as cypermethrin Assume same as cypermethrin 0.69 

DDVP (Assume 

breakdown 

product of naled 

listed below) 

Deltamethrin NA .003B (EC50) x 0.5 = .0015 Daphnia magna/ Acute invertebrates 0.0015 

Diazinon 1gf 0.105A Acute invertebrates 0.105 

Dicamba, 

dimethylamine salt 8.75d

61A (Based on 

lowest toxicity values 

of dicamba) 

Acute nonvascular plants 8.75 
John S. Sanders, Ph.D. 

May 29, 2009 Page 11 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Dicamba, sodium 

salt 8.75d

61A (Based on 

lowest toxicity values 

of dicamba) 

Acute nonvascular plants 8.75 

Dicofol NA 80B (EC50) x 0.5 = 40 Daphnia magna/Acute invertebrate 40 

Dimethoate 1.4fe 0.5A Chronic invertebrates 0.5 

Disulfoton .3e .01A Chronic invertebrates .01 

Diuron 2g 2.4A Acute nonvascular plants 2 
John S. Sanders, Ph.D. 

May 29, 2009 Page 12 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Endosulfan 42e .07A Chronic invertebrates .07 

EPTC NA 810A Chronic invertebrates 810 

Esfenvalerate NA .017A Chronic invertebrates .017 

Ethalfluralin NA 0.4A Chronic fish 0.4 

Ethoprop NA 22A Acute invertebrates 22 
John S. Sanders, Ph.D. 

May 29, 2009 Page 13 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Fenamiphos1 .7f .12B (NOEL) x 1 = .12 Daphnia magna/ Chronic invertebrates 0.12 

Fenoxycarb NA .0016B (NOEL) x 1 = .0016 Daphnia magna/ Chronic invertebrates 0.0016 

Fenpropathrin NA .013B (NOEL) x 1 = .013 Pimephales promelas/ Chronic fish 0.013 

Fipronil NA 6.6B (NOEL) x 1 = 6.6 Oncorhynchus mykiss/ Chronic fish 6.6 

gammaCyhalothrin 35e 0.00042B (LC50) x .5 = .00021 Gammarus pseudolimnaeus/ Acute invertebrates 0.00021 

Glyphosate 700a 1800A Chronic fish 700 
John S. Sanders, Ph.D. 

May 29, 2009 Page 14 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Glyphosate, 

diammonium salt 

Assume 

same as 

glyphosate 

Assume same as 

glyphosate Assume same as glyphosate Assume same as glyphosate 

Glyphosate, 

isopropylamine 

salt 

Assume 

same as 

glyphosate 

42450A Acute fish Assume same as glyphosate 

Glyphosate, 

monoammonium 

salt 

Assume 

same as 

glyphosate 

Assume same as 

glyphosate Assume same as glyphosate Assume same as glyphosate 

Glyphosate, 

potassium salt 

Assume 

same as 

glyphosate 

Assume same as 

glyphosate Assume same as glyphosate Assume same as glyphosate 

Hexazinone 230e 7A Acute nonvascular plants 7 

Hydramethylnon1 NA 5B (EC50) x 1 = 5 Chlorella sp./ Acute nonvascular plants 5 
John S. Sanders, Ph.D. 

May 29, 2009 Page 15 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Imidacloprid NA 1.05A Chronic invertebrates 1.05 

lambdaCyhalothrin 35e .0019B (NOEL) x 1 = .0019 Daphnia magna/ Chronic invertebrates 0.0019 

Linuron 1.4e 0.09A Chronic invertebrates 0.09 

Malathion 100f .000026A Chronic invertebrates .000026 

MCPA 3.5e 170A Acute vascular plants 3.5 

MCPA, 

dimethylamine salt 130A Acute vascular plants Assume same as MCPA 
John S. Sanders, Ph.D. 

May 29, 2009 Page 16 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

MCPA, 2-ethyl 

hexyl ester 

Assume 

same as 

MCPA 

20A Acute vascular plants Assume same as MCPA 

MCPA, isooctyl 

ester 

Assume 

same as 

MCPA 

20A (Assume same 

as MCPA, 2-ethyl 

hexyl ester) 

Assume same as MCPA, 2-

ethyl hexyl ester 

Assume same as 

MCPA 

Metalaxyl 420e 1200B (NOEL) x 1 = 1200 Daphnia magna/ Chronic invertebrates 420 

Methidathion 0.7e 0.66A Chronic invertebrates 0.66 

Methiocarb NA 0.1A Chronic invertebrates 0.1 

Methomyl 175d 0.7A Chronic invertebrates 0.7 
John S. Sanders, Ph.D. 

May 29, 2009 Page 17 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Methyl 

isothiocyanate 

(Assume source is 

dazomet, metam 

potassium or 

metam sodium) 

50h 25.6A (metam sodium) Acute fish 25.6 

Methyl parathion 1f 0.25A Chronic invertebrates 0.25 

Metolachlor 70f 1A Chronic invertebrates 1 

S-metolachlor 

70f

(metolachl

or) 

1A (metolachlor) Chronic fish 1 

Metribuzin 70f 1.29A Chronic invertebrates 1.29 
John S. Sanders, Ph.D. 

May 29, 2009 Page 18 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Molinate 20c 105A Acute Fish 20 

Naled (assume 

source of detected 

DDVP) 

14e 0.0058A Chronic invertebrates 0.0058 

Napropamide 700e 1100A Chronic fish and chronic invertebrates 700 

Norflurazon 280e 9.7A Acute nonvascular plants 9.7 

Oryzalin 35e 42A Acute nonvascular plants 35 

Oxadiazon 35e 0.88B (NOEL) x 1 = .88 Oncorhynchus mykiss/ Chronic fish 0.88 
John S. Sanders, Ph.D. 

May 29, 2009 Page 19 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Oxamyl 50c 90A Acute invertebrates 50 

Oxyfluorfen 20e 0.29A Acute nonvascular plants 0.29 

Paraquat 

dichloride1 3.2e .55B (EC50) x 1 = .55 Navicula pelliculosa/ Acute nonvascular plant 0.55 

Pendimethalin 280e 5.4A Acute nonvascular plants 5.4 

Permethrin 350e 0.0014A Chronic invertebrates 0.0014 

Phorate .7d 0.21A Chronic invertebrates 0.21 
John S. Sanders, Ph.D. 

May 29, 2009 Page 20 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Phosmet 140e 0.8A Chronic invertebrates 0.8 

Prodiamine NA 1.5B (NOEL) x 1 = 1.5 Daphnia magna/ Chronic invertebrates 1.5 

Prometon 100f 98A Acute nonvascular plants 98 

Prometryn 28e 1A Acute nonvascular plants 1 

Propanil 35e 9.1A Chronic fish 9.1 

Propargite 140e 9A Chronic invertebrates 9 
John S. Sanders, Ph.D. 

May 29, 2009 Page 21 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Propiconazole 91e 93A Acute nonvascular 91 

Propoxur NA 5.5A Acute invertebrates 5.5 

Propyzamide 

(pronamide) 2g 600A Chronic invertebrate 2 

Pyriproxyfen NA .01B (NOEL) x 1 = .01 Daphnia magna/ Chronic invertebrates 0.01 

Siduron NA .13B (LC50) x .5 

= .065 

Lepomis macrochirus/ Acute 

fish 0.065 

Simazine 4a 36A Acute nonvascular 4 
John S. Sanders, Ph.D. 

May 29, 2009 Page 22 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Terbuthylazine NA 3.2B (EC50) x 1 = 3.2 Selenastrum capricornutum/ Acute nonvascular plants 3.2 

Tetrachlorvinphos1 210e 1.9B (EC50) x .5 = .95 Daphnia magna/ Acute invertebrates 0.95 

Thiobencarb 1c 1A Chronic invertebrates 1 

Triallate 91e 13A Chronic invertebrates 13 
John S. Sanders, Ph.D. 

May 29, 2009 Page 23 

Common name 

MCL or 

Lowest 

Drinking 

Water 

Concentrati

on for 

Protection 

of Human 

Health 

(ppb) 

Lowest U.S. EPA 

Aquatic Acute or 

Chronic Benchmark 

(A), or Lowest OPP 

Database Value 

(B) Multiplied by 

Level of Concern2

(LOC) Factor (ppb) 

Test type (A) or Species/test 

type (B) 

Lowest Aquatic 

Toxicity Value o

Human Health 

Protective Level f

Drinking Water 

Tribufos (Folex – 

S,S,S- tributyl 

phosphorotrithioat

e) 

NA 1.56A Chronic invertebrates 1.56 

Triclopyr, butoxy 

ethyl ester NA 100A (triclopyr) Acute nonvascular 100 

Triclopyr, 

triethylamine salt NA 100A (triclopyr) Acute nonvascular 100 

Trifluralin 4g 1.14A Chronic fish 1.14 
John S. Sanders, Ph.D. 

May 29, 2009 Page 24 

1 Single detection 2 Factor used by he U.S. EPA to calculate aquatic life benchmarks. See text. a CDPH and U.S. EPA MCL b U.S. EPA MCL cCDPH MCL d National Academy of Sciences HA (noncancer) eU.S. EPA Integrated Risk Information System reference dose (noncancer) fU.S. EPA HA (noncancer) gU.S. EPA HA (cancer) hCalifornia notification level 

NA=not available