Open literature Review Summary 

Chemical Name: Atrazine 

CAS No: 1912-24-9

ECOTOX Reference Number and Citation: 164775 

McMahon TA; Romansic JM; Rohr JR. 2013. Nonmonotonic and Monotonic Effects of Pesticides 

on the Pathogenic Fungus Batrachochytrium dendrobatidis in Culture and on Tadpoles. Environ. 

Sci. Technol. 47(14): 7958-7964. 

Purpose of Review: Registration Review

Date of Assessment: 4/5/2015 

Brief Summary of Study Findings: This study examined the effects of atrazine and chlorothalonil 

on the survival of Bd both in culture and on Osteopilus septentrionalis (Cuban treefrog) tadpoles. 

In the concentration range tested (0.011 to ϮϭϮʅŐͬ>) atrazine reduced levels of Bd growth in 

culture and reduced Bd growth on tadpoles as compared to controls. Overall tadpole survival 

was impacted by Bd but not atrazine exposure. The atrazine treated tadpoles had significant 

decreases in the time to death as compared to controls and increased mass of tadpoles as 

compared to the chlorothalonil group. 

Methods: Bd culture was prepared using Bd stock isolated from Rana Catesbenia from Savanah 

River site, SC and culturing in tryptone broth. Zoospores were grown on agar plates and used for 

experimental inoculation. 

Effects of the two pesticides on Bd growth in culture were measured after one and two weeks. 

Chlorothalonil was tested at 0.0176, 0.176, 1.76, and 17.6 ʅŐͬ> and atrazine at 1.06, 10.6, 58, 

ĂŶĚϭϬςʅŐͬ>͖ďŽƚŚ pesticides were technical grade, purity >98% (Chemservice, West Chester, 

PA) and two controls were prepared for each pesticide (water and solvent; acetone). Actual 

concentrations of the stock solutions were measured at 176 ƵŐͬ>ĐŚůŽƌŽƚŚĂůŽŶŝůĂŶĚϭϬςƵŐͬ>

atrazine. Culture tubes were incubated at 23 °C for either one or two weeks and Bd 

concentrations were quantified at the one and two week time increments based on 20-Ƶ>

aliquots on a hemocytometer. 

Effects of the two pesticides on Bd growth in culture were also measured based on daily Bd

growth for 8 days and 10 treatments based on 10-fold serial dilutions of the pesticide 

(chlorothalonil: 0.000176, 0.00176, 0.0176, Ϭ͘ϭϳς͕ϭ͘ϳς͕Θ͘Θ͕ϭϳ͘ς͕ϯρ͘Ϯ͕εϬ͘Ϯ͕ĂŶĚϭϳςʅŐͬ>͖ĂŶĚ

atrazine: Ϭ͘Ϭϭϭ͕Ϭ͘ϭϬς͕ϭ͘Ϭς͕ϭϬ͘ς͕Ϯϯ͕ρΘ͕ϳϳ͕ϭϬς͕ϭρε͕ĂŶĚϮϭϮʅŐͬ>Ϳ. Effects were determined 

by measuring changes in Bd density using spectrophotometric analysis. 

Effects of the two pesticides on Bd growth in Osteopilus septentrionalis (Cuban treefrog) 

tadpoles were also determined based on four concentrations of technical grade chemical 

(chlorothalonil: 0.0176,0.176, 1.76, and 1ϳ͘ςʅŐͬ>͖ĂŶĚĂƚƌĂnjŝŶĞ͗ϭ͘Ϭς͕ϭϬ͘ς͕ρΘ͕ĂŶĚϭϬς

ʅŐͬ>Ϳ͘ Tadpoles were collected from three clutches naturally oviposited in outdoor wading pools 

and were completely mixed before being distributed among treatment groups. All tadpoles 

were Gosner stage 25 with an average tadpole weight at the start of the experiment of 0.086 ± 
0.01 g (mean± SEM based on 10 randomly selected tadpoles). dĂĚƉŽůĞƐǁĞƌĞŚŽƵƐĞĚŝŶρϬϬŵ>

glass mason jars and kept on a 14:10 light/dark cycle. Water was exchanged weekly and Bd and 

pesticide treatments re-dosed after each water change. Bd exposure was attained through 

ŝŶŽĐƵůĂƚŝŽŶǁŝƚŚϯŵ>ŽĨBd+

 inoculum (concentration of Bd+ was 6.0 x 104 njŽŽƐƉŽƌĞƐͬŵ>Ϳ͘ Bd

was quantified based on PCR analysis of tadpole mouthparts. 

Results: Atrazine exposure resulted in a monotonic negative impact on Bd growth in culture, but 

ŽŶůLJƚŚĞŚŝŐŚĞƐƚĐŽŶĐĞŶƚƌĂƚŝŽŶƚĞƐƚĞĚϭϳ͘ςƵŐͬ>ƐŝŐŶŝĨŝĐĂŶƚůLJƌĞĚƵĐĞĚĐŽŶĐĞŶƚƌĂƚŝŽŶƐĐŽŵƉĂƌĞĚ

to controls. For daily Bd growth as measured using spectrophotometric analysis after correcting 

for pesticide effect on absorbance, all atrazine concentrations significantly reduced Bd growth as 

compared to controls except for the 0.1 ug/l concentration. For Bd growth on tadpoles, atrazine 

exposure resulted in significantly less Bd growth at all concentrations as compared to controls. 

The author also reported that tadpoles exposed to atrazine died sooner than control animals or 

those exposed to chlorothalonil (512.4 ±11.18, 533.8 ± 10.06, 534.5 ± 10.38 h, respectively; F1, 

136 =4.98, p = 0.03) and higher mass than tadpoles exposed to chlorothalonil treatments 

(mean ± SEM: 0.26 ±0.02 g and 0.21 ± 0.01 g, respectively; F1, 129 = 8.21, p = 0.005).

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 effects of atrazine on Bd growth and 

some limited information on tadpole growth and time to death after atrazine exposure. 

Limitations of the Study: Regarding the effect of atrazine on survival time (tadpoles died 

sooner) and increased mass, no supporting raw data was reported to support this analysis and 

the effect is not associated with a definitive concentration. 

Water quality parameters not reported in study. 

Reviewer: Colleen M. Rossmeisl, DVM; ERB3, Environmental Fate and Effects Division 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 17:54:52 -04'00'