APPENDIX A. Supporting Environmental Fate Data 

(8 pages) 

Hydrolysis (161‐1)

Based on the results of the hydrolysis study (MRID 40431319), atrazine did not hydrolyze at pH

5, 7, and 9.  It was concluded that hydrolysis is not an important degradation mechanism for

atrazine.

Aquatic Photodegradation (161‐2)

The study (MRID 00024328) showed that [14C]atrazine degraded with a registrant‐calculated

half‐life of 25 ± 2 hours in unbuffered aqueous solutions (initial pH 6.8) that were irradiated

with a 125‐W mercury vapor lamp at 15oC; in unbuffered aqueous solutions sensitized with 1%

acetone, the half‐life decreased to 4.9 ± 0.5 hours.

The study (MRID 42089904) showed that in buffered solution at pH 7, atrazine did not

degrade under natural sunlight conditions with a calculated half‐life of approximately 335 days

from a rate constant of 1.72 x 10‐4 hours‐1. However, under artificial light irradiation with

mercury arc lamp, atrazine degraded at a faster rate with a half‐life of approximately 17 hours.

Due to the lack of a comparison of the mercury arc lamp with natural sunlight, and no UV‐VIS

spectrum of atrazine in pH 7, the study is considered to be supplemental. For the purpose of

risk assessment, the half‐life result of 335 days with natural sunlight should be considered.

Information is requested on the intensity of the mercury arc lamp and the US‐VIS spectrum of

atrazine in pH 7 for more accurate review.

Soil Photodegradation (161‐3)

The study (MRID 40431320) was investigated with both natural and artificial sunlight

exposures. The results with artificial sunlight showed a half‐life of 5.3 days, when corrected

with dark control, the half‐life was 7.4 days.  With natural sunlight, the half‐life was determined

to be 12 days.

The study (MRID 42089905) was investigated with artificial sunlight exposure. The half‐life

under non‐irradiated conditions was 267 days, and the half‐life under irradiated conditions was

38 days. The net half‐life attributable to photodegradation is 45 days.

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Aerobic Soil Metabolism (162‐1)

The study (MRID 42089906, MRID 40431321) with atrazine applied on California loam soil

showed an aerobic half‐life of approximately 146 days. The degradation products were

identified as G‐30033, G‐28279, G‐28273, and G‐34048.

The second study (MRID 40629303) was also considered supplemental. The calculated half‐life

was 146 days under non‐sterile aerobic conditions and to be very slow under sterile conditions.

The degradation products were identified as G‐30033, G‐28279, G‐28273, G‐34048, GS‐17794,

and GS‐17792.

Anaerobic Soil Metabolism (162‐2)

The study (MRID 40431321) was considered supplemental. The calculated half‐life for atrazine

under anaerobic conditions was approximately 159 days. The degradation products G‐30033

and G‐28279 were present at all sampling times in both soil extracts and supernatant water; G‐

28273 and G‐34048 were also present, but not at all sampling times.

The half‐life value was not established in the second study (MRID 40629303).  The degradation

products were identified as G‐30033, G‐28279, G‐28273, and G‐34048.  The study (MRID

42089906) with atrazine applied on California loam soil showed that when flooded with water,

atrazine degraded with a calculated half‐life of approximately 159 days. The degradation

products were identified as G‐30033, G‐28279, G‐28273, and G‐34048.

Anaerobic Aquatic Metabolism (162‐3)

The study (MRID 40431323) is acceptable. The combined water/sediment (sandy clay) half‐life

of atrazine was calculated as 608 days (330 days in sediment; 578 days in water).  Production of

volatile material was minimal.  Bound residues increased with time, but leveled to about 10% of

applied dose by month 12.  About 70% of radioactivity in water and 4% in sediment were

associated with parent atrazine after 12 months. Metabolites were present at low levels (G‐

30033, 4.7%; G‐34048, 5%; and G‐28279, 1.4%).

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Mobility/Adsorption/Desorption (163‐1)

The study (MRID 40431324) was acceptable and partially contributed to fulfill data

requirements for the mobility of atrazine.  A batch equilibrium adsorption/desorption study

was conducted with four different soils and four different concentrations of 14C‐label atrazine.

The Kads constants ranged from 0.427 (sand) to 2.030 (loam soil). The Kdes constants ranged

from 2.261 (silty loam soil) to 14.90 (sandy loam soil).  Kocs ranged from 55.0 (sandy loam soil)

to 135 (loam soil) for the adsorption phase. These results indicated that atrazine was not

strongly adsorbed onto soil particles and that desorption occurred readily.

A batch‐equilibrium adsorption/desorption was conducted with four different soils and four

different concentrations of 14C‐label G‐28273 (MRID 40431327). The Kads constants ranged

from 0.108 (sand) to 0.800 (silty clay loam). The Kdes constants ranged from 1.172 (silty clay

loam) to 6.620 (sandy loam).  Koc ranged from 11.6 (sandy loam) to 59.5 (silt loam) for the

adsorption phase. These results indicated that G‐28273 was not strongly adsorbed onto soil

particles and that desorption occurred readily.

A batch‐equilibrium adsorption/desorption was conducted with four different soils and four

different concentrations of 14C‐label G‐28279 (MRID 40431325). The Kads constants ranged

from 0.225 (sand) to 1.144 (loam soil). The Kdes constants ranged from 1.784 (silty loam) to

12.479 (sand). Koc ranged from 35.1 (sandy loam) to 82.3 (silty loam) for the adsorption phase.

These results indicated that G‐28279 was not strongly adsorbed onto soil particles and that

desorption occurred readily.

A batch‐equilibrium adsorption/desorption was conducted with four different soils and four

different concentrations of 14C‐label G‐30033 (MRID 40431328). The Kads constants ranged

from 0.116 (sand) to 0.963 (silty clay loam). The Kdes constants ranged from 8.104 (silty clay

loam) to 12.87 (silt loam).  The Koc ranged from12.8 (sandy loam) to 66.5 (silty loam) for the

adsorption phase. These results indicated that G‐30033 was not strongly adsorbed onto soil

particles and that desorption occurred readily.

A batch‐equilibrium adsorption/desorption was conducted with four different soils and four

different concentrations of 14C‐label G‐34048 (MRID 40431326). The Kads constants ranged

from 5.518 (sand) to 22.26 (silty clay loam). The Kdes constants ranged from 8.104 (silty clay

loam) to 12.87 (silt loam). The Koc ranged from 350 (sand) to 680 (silty loam) for the adsorption

phase.  These results indicated that G‐34048 was the strongest adsorbed among the atrazine

degradates.

In a series of studies (MRID 40431329 to 40431334) with soil thin‐layer chromatography, only

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hydroxyatrazine (G‐34048), showed low mobility, others (atrazine, diaminochlorotriazine (G‐

28273), deisopropylatrazine (G‐28279), and deethylatrazine (G‐30033)

showed high mobility in the soil environment.

The adsorption/desorption characteristics of hydroxyatrazine (G‐34048), diaminochlorotriazine

(G‐28273), deisopropylatrazine (G‐282279), deethylatrazine (G‐30033) are summarized in Table

1.

Table1:  Soil Sorption Coefficients for  Atrazine Degradation Products

Degradation

Product Kf Kd Koc References

G‐28273 0.16‐1.56 0.108‐0.800 30.65‐75.96

MRID 41257904

MRID40431327

MRID 40431333

G‐28279 0.16‐2.7 0.422‐6.08 35.1‐82.3

MRID 41257906

MRID 40431331

MRID 40431325

G‐30033 0.06‐1.02 0.116‐0.963 12.15‐44.90

MRID 41257906

MRID 40431334

MRID 40431334

G‐34048 1.98‐389.6 1.643‐8.165 38.50‐155.34

MRID 41257902

MRID 40431332

MRID 40431326

The results of the batch‐equilibrium adsorption/desorption studies indicate that the

dealkylated degradation products are as likely (or even more likely) to leach to ground water as

parent atrazine.  

Terrestrial Field Dissipation (164‐1)

The results of a field dissipation study with corn soil at Donaldsonville, Georgia (MRID:

42165504) predicted a half‐life of 12.75 days with residues decreasing to less than 0.4 ppm on

the 27‐day sampling.  AAtrex® Nine‐O® was applied at a rate of 4.4 lb a.i./ac to a test corn plot

of sandy loam soil on June 14, 1986. The degradation products, G‐34048, G‐30033, and G‐ 

28279 found in the top 0‐6" depth were significant lower (< 0.05 to 0.31 ppm) compared to the

parent residues which ranged < 0.05 to 0.73 ppm. The leaching data for parent atrazine and its

degradation products at depths below 6‐12" soil depth were generally below the screening

level of 0.05 ppm.

The results of a field dissipation study with bare ground at Donaldsonville, Georgia (MRID

42165505) predicted a half‐life of 38.52 days with residues decreasing to less than 0.5 ppm on

the 451‐day sampling. AAtrex® Nine‐O® was applied at a rate of 18.0 lb a.i./ac to a field plot

of unvegetated sandy loam soil on June 27, 1986. The degradation products, G‐34048, G‐ 

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30033, and G‐28279 found in the top 0‐6" depth were significant lower (<0.05 to 2.16 ppm)

compared to the parent residues which ranged <0.05 to 6.98 ppm. The leaching data for parent

atrazine and its degradation products at depths below 6‐12" soil depth were generally below

the screening level of 0.05 ppm.

The results of a field dissipation study with bare ground at Ripon, California (MRID 40431336,

42165506) predicted a half‐life of 102.5 days. Atrazine (90% dry flowable) was applied at a

nominal concentration of 18 lb ai/ac to a field plot of unvegetated sandy loam soil in July 1986.

In the 0‐ to 6‐inch depth, atrazine was 4.75 ppm (4.75 ppm total residues) immediately after

treatment, decreased to 1.05 ppm (1.20 ppm total) at 90 days, and 0.67 ppm (0.94 ppm total)

at 120 days, increased to 5.31 ppm (6.24 ppm total) at 180 days, then decreased to 0.50 ppm

(0.63ppm total) at 267 days and 0.20 ppm (0.26 ppm total) at 358 days post‐treatment. The

major degradation products were G‐34048, G‐30033, and G‐28279.

The results of a field dissipation study with bare ground at Hollandale, Minnesota (MRID

40431337, 42165507) indicated a half‐life of 261 days. Atrazine (90% dry flowable) was

applied at a nominal concentration of 20 lb ai/ac to a field plot of un‐vegetated loam soil in July

1986. In the 0‐ to 6‐inch depth, atrazine was 4.23 ppm (5.06 ppm total residues) immediately

after treatment, increased to 10.15 ppm (11.66 ppm total) at 14 days, decreased to 5.34 ppm

(6.75 ppm total) at 28 days, and was 2.90 ppm (4.88 ppm total) at 360 days post‐treatment. The

major degradation products were G‐34048. G‐30033, and G‐28279.

The results of a field dissipation study with a corn soil at Hollandale, Minnesota (MRID

40431339, 42165508) yielded a half‐life of 261 days. Atrazine (90% dry flowable) was applied

at a nominal concentration of 4.4 lb ai/ac to a field plot of loam soil planted to corn in July

1986.  In the 0‐ to 6‐inch depth, atrazine was 1.20 ppm (1.37 ppm total residues) immediately

after treatment, increased to 1.40 ppm (1.59 ppm total) at 2 days, ranged from 0.48 to 1.00

ppm (0.90‐ 1.17 ppm total) with no discernable pattern between 7 and 290 days, and was 0.37

ppm (0.91ppm total) at 360 days post‐treatment. The major degradates were G‐34048. G‐

30033, and G‐28279.

The results of a field dissipation study with corn soil in Ripon, California (MRID 40431338,

42165509) indicated a half‐life of 58 days. Atrazine (90% dry flowable), applied at a nominal

concentration of 3.96 lb ai/ac to a field plot of sandy loam soil planted to corn in July 1986. In

the 0‐ to 6‐inch depth, atrazine was 1.15 ppm (1.15 ppm total residues) immediately after

treatment, increased to 2.82 ppm (2.82 ppm total) at 7 days, decreased to 1.18 ppm (1.18 ppm

total) at 14 days, decreased to 0.50 ppm (0.74 ppm total) at 60 days, and was 0.02 ppm (0.53

ppm total) at 358 days post‐treatment. The major degradation products were G‐34048, G‐

30033, and G‐28279.

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Forestry Field Dissipation (164‐3)

A field dissipation half‐life of 87 days was estimated for exposed soil in a forestry study at

Oregon City, Oregon (MRID Nos: 40431340, 42041405). Atrazine (90% G) was applied

aerially at 4 lb ai/ac to 10 acres of an immature Douglas fir forest on April 4, 1985. In tree

foliage samples, atrazine was 168.2 ‐ 294.2 ppm immediately post‐treatment, 76.7 ‐ 88.0 ppm

at 7 days, 6.6 ‐ 10.5 ppm at 29 days, and 1.6 ‐ 3.2 ppm at 88 days post‐treatment. The registrant

calculated half‐life for atrazine in foliage was 13 days.

In leaf litter samples, atrazine was 73.1 ‐ 114.2 ppm immediately post‐treatment, 21.8 ‐ 27.9

ppm at 29 days, 7.2 ‐ 8.1 ppm at 88 days, and 0.60 ‐ 3.4 ppm at 364 days post‐treatment; the

registrant calculated half‐life was 66 days. In soil (0‐ to 6‐inch depth) that was not covered with

leaf litter, atrazine concentrations were variable with no discernible pattern, ranging from

0.075 to 4.3 ppm.

G‐30033 was isolated at up to 0.118 ppm. In the 6‐ to 12‐ and 12‐ to 18‐inch soil depths,

atrazine was < 0.05 to 0.432 ppm and < 0.05 to 0.110 ppm, respectively. In soil under leaf litter,

atrazine concentration were variable in the 0‐ to 6‐inch depth, ranging from 0.077 to 4.7 ppm,

and were #0.088 ppm in the 6‐ to 12‐ and 12‐ to 18‐inch depths.

Long‐Term Terrestrial Field Dissipation (164‐5)

The results of a long‐term field dissipation study with corn soil at Hollandale, Minnesota,

(MRID 40431339, 42089911) predicted a half‐life of 402 days with an r2of 0.81. In the 0‐6"

soil samples, detectable residues of atrazine, G‐30033, and G‐34048 were found at 451, 510,

668, 847, 1032, 1211, and 1389 DAT (days after treatment), and detectable residues of G‐28279

were found at 451, 510, 668, 847, and 1032 DAT. In the 6‐12" soil samples, detectable residues

of atrazine were found at 510, 668, 847, 1032, and 1211 DAT, detectable residues of G‐30033

were found at 668, 847, and 1032 DAT, and detectable residues of G‐34048 were found at 451,

510, 668, 847, 1032, 1211, and 1389 DAT. The 12‐18" soil samples produced no detectable

residues of atrazine, G‐28279, G‐30033, or G‐34048. No detectable residues of atrazine, G‐ 

28279, or G‐30033 were found in the 18‐24" soil samples; however, detectable residues of G‐ 

34048 were found at 1211 and 1389 DAT. In the 24‐36" soil samples, no detectable residues of

atrazine, G‐28279, G‐30033, or G‐34048 were found.

The results of a long‐term field dissipation study with bare ground at Hollandale, Minnesota,

(MRID 40431337, 42089912) predicted a half‐life of 261 days with an r2of 0.94. In the 0‐6"

soil samples, detectable residues of atrazine, G‐30033, and G‐34048 were found at 449, 498,

659, 839, 1020, 1200, and 1378 DAT, and detectable residues of G‐28279 were found at 449,

498, 659, 839, and 1020 DAT. Detectable residues of atrazine and G‐34048 were found in the 6‐ 

12" soil samples at 449, 498, 659, 839, 1020, and 1200 DAT, detectable residues of G‐30033

6
were found at 449, 498, 659, 839, and 1200 DAT. In the 12‐18" soil samples, detectable

residues of atrazine were found at 449, 498, 659, 839, 1020, 1200, and 1378 DAT, no detectable

residues of G‐28279 or G‐30033 were found, detectable residues of G‐34048 were found at

449,659, and 1200 DAT. In the18‐24" soil samples, detectable residues of atrazine were found

at 449, 498, 659, 839, and 1020 DAT, no detectable residues of G‐28279 were found, detectable

residues of atrazine were found only at 1020 DAT, detectable residues of G‐28279 were found

449 and 498 DAT, detectable residues of G‐30033 were only found at 498 DAT, and no

detectable residues of G‐34048 were found.

The results of a long‐term field dissipation study with corn soil at Ripon, California, (MRID

40431338, 42089909) predicted a half‐life of 102 days with an r2of 0.84. In the 0‐6" soil

samples, detectable residues of atrazine were found at 552 DAT, no detectable residues of G‐ 

30033 were found, and G‐34048 were found at 460, 552, 726, 873, 1045 DAT samples. In the 6‐ 

12" soil samples, detectable residues of atrazine were found at 460 and 552 DAT, detectable

residues of G‐28279 and G‐30033 were found only in the 460 DAT samples, and detectable

residues of G‐34048 were found at460, 552, 873, and 1045 DAT soils samples. At the 12‐18"

soil depth, detectable residues of atrazine were found at 460 DAT only, no detectable residues

of G‐28279 or G‐30033 were found, and detectable residues of G‐34048 were found in the 460,

552, and 873 DAT soil samples. In the 18‐24" soil samples, detectable residues of atrazine and

G‐28279 were found in 460 and 552 DAT soil samples, no detectable residues of G‐30033 were

found, and detectable residues of G‐34048 were found in the 460 and 873 DAT soil samples. No

detectable residues of G‐28279 were found in the 24‐36" soil samples, while detectable

residues of atrazine and G‐30033 were found at 460 DAT, and residues of G‐34048 were found

at 460,552, and 873 DAT.

The results of a long‐term field dissipation study with bare ground at Ripen, California, (MRID

40431336, 42089910) predicted a half‐life of 110 days with an r2of 0.92. In the 0‐6" soil

samples, detectable residues of atrazine and G‐30033 were found only at 460 DAT, and

detectable residues of G‐34048 were found in 460, 552, and 837 DAT samples. No detectable

residues of atrazine or G‐28279 were found in the 6‐12" soil samples, detectable residues of G‐ 

30033 were found only at 552 DAT, and detectable residues of G‐34048 were found in the 460,

552, and 873 DAT soil samples. No detectable residues of atrazine, G‐28279, or G‐33033 were

found in the 12‐18" soil samples, while detectable residues of G‐34048 were found in the 460,

552, and 873 DAT soil samples. In the18‐24" soil samples, no detectable residues of atrazine,

G‐28279, or G‐30033 were found, while detectable residues of G‐34048 were found in the 460,

552, and 873 DAT soil samples. Detectable residues of atrazine, G‐28279, G‐30033, and G‐ 

34048 were found in the 24‐36" soil samples for 460 DAT and residues of atrazine and G‐34048

were also found at 873 DAT.

7
8

Bioaccumulation in Fish (165‐4)

Based on an accepted study (MRID: 40431344), total [14C]atrazine residues accumulated in

bluegill sunfish with maximum bioconcentration factors of 7.7x, 12x, and 15x in edible tissues

(body, muscle, skin, skeleton), non‐edible tissues (fins, head, internal organs), and whole fish,

respectively, during 28 days of exposure to uniformly ring‐labeled [14C]atrazine at 0.01 ppm in a

flow‐through system. After 21 days of depuration, [14C]atrazine were 0.21 ppm in edible tissues,

0.38 ppm in non‐edible tissues, and 0.28 ppm in whole fish; depuration rates were 74, 76, and

78%, respectively.

Spray Drift Data Requirements (201‐1, 202‐1)

The guidelines require data of droplet size spectrum and drift field evaluation. No atrazine

specific spray drift studies were reviewed. The registrant, Novartis, is a member of the Spray

Drift Task Force (SDTF). The SDTF has completed and submitted to the Agency a series of

studies intended to characterize spray droplet drift potential due to various factors, including

application methods, application equipment, meteorological conditions, crop geometry and

droplet characteristics. EFED is currently evaluating these studies. After its review, the Agency

will determine whether a reassessment is warranted of the potential risks from the application

of atrazine to non‐target organisms.