Open literature Review Summary 

Chemical Name: Atrazine 

CAS No: 1912-24-9

ECOTOX Reference Number and Citation: 165358 

Rohr J.R. and B.D. Palmer. 2013. Climate Change, Multiple Stressors, and the Decline of 

Ectotherms. Conservation Biology. 27(4): 741-751. 

Purpose of Review: Registration Review

Date of Assessment: 10/23/2015 

Brief Summary of Study Findings: 

This study examined the effects of temperature (22oC or 27 oC), moisture (wet or dry) and 

atrazine (0, 4, 40 and 400 μg/L) on the survival, growth, behavior and foraging of streamside 

salamanders (Ambystoma barbouri). Changes in temperature and moisture alone caused 

significant loss of mass and mortality with atrazine exposure having an additive effect by 

decreasing water conserving behavior, foraging efficiency, mass and time to death. Compared to 

controls, at the end of the experiment there was a significant negative effect on the percent of 

mass change at all atrazine concentrations tested as well as a negative association between 

atrazine concentration and time of survival. Temperature had the greatest impact on individual 

fitness, with higher temperatures having a higher impact on survival than moisture. 

Methods: Streamside salamanders were exposed to atrazine during their larval stage from the 

embryo stage (April 2002) to metamorphosis (August 2002). No further atrazine exposure 

occurred after metamorphosis. Methods were briefly summarized in the study and the reader is 

referred to Rohr 2004 for further details. 31 eggs were placed into 48 aquaria containing 9.5 L 

at pH of 8 and temperature of 15මC. Egg clutches were collected from Fossil Creek (Jessamine 

County, KY). Four atrazine concentrations, each containing solvent DMSO, were tested at 0, 4, 

40, and 400 ppb (80% pure atrazine). Water was changed weekly and the chemical reapplied 

with weekly measurements of atrazine taken and reported as κ͘ερʅŐͬ>;^Ϭ͘ϯϬͿ͕ϯΘ͘ϳϬʅŐͬ> (SE 

Ϯ͘ϭκͿ͕ĂŶĚϯΘς͘ϬκʅŐͬ>;SE 23.24). 

For the 11 week post metamorphosis observation period 160 terraria were constructed. 3 

metamorphs from each treatment group were placed in a terrarium. Two incubators were 

established at 22ම and 27ම. The experimental layout consisted of: 
Atrazine aquatic exposure 

concentration prior to 

metamorphosis (ug/L) 

Terrestrial temperature/moisture exposure matrix 

Incubator 1: 

22ම

Incubator 2: 

22ම

Incubator 3: 

27ම

Incubator 4: 

27ම

Wet Dry Wet Dry Wet Dry Wet Dry 

0 

4 

40 

400 

1

 dry = 42% moisture by weight, wet = 78% moisture by weight 

Temperature selection was based on the natural conditions of salamanders in Kentucky (22මͿ

ǁŝƚŚƚŚĞϮϳමC temperature intended to be both representative of a possible range of 

temperatures associated with global warming but also within the bounds of current natural 

conditions (Kentucky temperatures reach 30.5මC in summer). Cool and moist conditions were 

anticipated to provide the most favorable conditions and warm and dry conditions expected to 

be associated with the most significant adverse effects. 

Each terrarium was provided one cricket per salamander per week. Individual salamanders were 

denoted by toe clipping. Thirteen times (approximately once weekly) during the procedure 

observations were made if salamanders were in refuge (under a refuge plate or buried), moving, 

huddled, or climbing up the walls of the terrarium. Mass and length were measured during the 

last week of the experiment. Survival was assessed once weekly when the terraria were weighed 

as it sometimes required disturbing buried salamanders. Foraging trials were conducted during 

the last week of the experiment where 4 crickets were placed in each terraria and number of 

crickets eaten and number of salamanders buried was recorded hourly for 4 hours. This was 

only conducted in the 22මC incubators due to high mortality at this point in the experiment in 

the 27මC terraria. 

Results: From the summary of results, the following interactions were noted: 

Endpoint measured NOAEC 

(ug/L) 

LOAEC 

(ug/L) 

Behavior – Huddling 4 40 

Behavior – Inactivity <4 4 

Behavior – In refuge 4 40 

Mass change <4 4* 

Survival >400 NA 

*p=0.054 at 40 ug/L atrazine 

Each square represents 

separate incubator conditions 

that contain 5 replicates 

(terrariums) with 3 

metamorphs in each replicate 
Significant effect was noted on certain behaviors at all atrazine concentrations; however, as 

presented, results were pooled from all temperature and moisture test conditions together 

making it difficult to separate out effects due to atrazine alone. Significant differences on 

behavior were also reported due to temperature and moisture changes when all atrazine 

exposure concentrations pooled. A significant effect on mass change was noted with atrazine 

exposure overall. A 4% change with each log 10 difference was noted at 27oC. 

In foraging trials (performed only on 22oC incubators due to high mortality in 27මC incubator 

groups), 1 hr after exposure most salamanders were not buried in wet or dry conditions. Under 

dry conditions, 1 hr after release of crickets, atrazine exposed salamanders had reduced 

foraging efficiency as evidenced by the number of crickets eaten per salamander. However, due 

to the effect of atrazine to reduce the number of salamanders in refuge under dry conditions, at 

2-4 hrs there was an increase in foraging efficiency as less salamanders were buried by 4 hrs. 

Under wet conditions, atrazine exposure was associated with a negative effect in foraging 

efficiency at all time points. The author noted the cumulative number of crickets eaten 

depended significantly on time, moisture and atrazine exposure. 

Description of Use in Document: Qualitative. This study is of sufficient quality for inclusion in 

risk assessment. 

Rationale for Use: The study provides information on amphibian growth, mortality and 

behaviors under different and changing environmental conditions; implications for multiple 

stressors in the environment; uncertainties identified are described below. 

Limitations of the Study: DMSO was used as the solvent without a negative control. Uncertainty 

exists in the use of DMSO as a solvent as it may accelerate the movement of chemicals across 

cell membranes. However, the author reported that no negative control was included as the 

solvent has not been shown to have effects on behavior, growth or survival in this species in a 

previous study (Rohr et al., 2003a). 

All results were only presented graphically, making it difficult to validate or further analyze the 

reported results. In addition, for certain endpoints, it was difficult to discern if the reported 

effects associated with atrazine exposure were from pooled results of all temperature and 

exposure concentrations or individual exposure regimens. As significant effects were seen due 

to changes in temperature and moisture alone, this made it challenging to differentiate a clear 

causation from atrazine exposure alone. 

The aqueous phase exposure portion of this study was previously reported under Rohr 2004. 

The 2004 study was previously reviewed (Open literature summary review, A. Pease and A. 

Blankenship, 2012). Concern was noted in the study review due to a possible fugal pathogen 

forming a white film on embryos, use of DMSO, no negative control, no raw data reported, 

unknown study duration, variation in results from 2002 to 2003, possible prior exposure of test 

organisms to atrazine, high loading rates and the lack of ammonia and nitrate reporting. 

Reviewer: Colleen M. Rossmeisl, DVM; ERB3, Environmental Fate and Effects Division 

References: 

COLLEEN 

ROSSMEISL

Digitally signed by COLLEEN 

ROSSMEISL 

DN: c=US, o=U.S. Government, 

ou=USEPA, ou=Staff, 

cn=COLLEEN ROSSMEISL, 

dnQualifier=0000069649 

Date: 2016.04.07 17:58:15 -04'00'
Rohr, J. R., A. A. Elskus, B. S. Shepherd, P. H. Crowley, T. M. Mc-Carthy, J. H. Niedzwiecki, T. 

Sager, A. Sih, and B. D. Palmer.2003a. Lethal and sublethal effects of atrazine, carbaryl, 

endosulfan, and octylphenol on the streamside salamander, Ambystoma barbouri. 

Environmental Toxicology and Chemistry 22:2385–2392. 

Rohr, J. R., A. A. Elskus, B. S. Shepherd, P. H. Crowley, T. M. McCarthy, J. H. Niedzwiecki, T. Sager, 

A. Sih, and B. D. Palmer. 2004. Multiple stressors and salamanders: effects of an herbicide, food 

limitation, and hydroperiod. Ecological Applications 14:1028–1040.