Open literature Review Summary 

Chemical Name: Atrazine 

CAS No: 1912-24-9

ECOTOX Reference Number and Citation: E160887 

Svartz GV; Herkovits J; Perez-Coll CS. 2012 Sublethal Effects of Atrazine on Embryo-Larval 

Development of Rhinella arenarum (Anura: Bufonidae). Ecotoxicology 21(4): 1251-1259. 

Purpose of Review: Registration Review 

Date of Assessment: 4/6/2015 

Brief Summary of Study Findings: This study examined the effects of atrazine exposure on

embryo-larval development of the common South American toad, Rhinella arenarum, 

Methods: Three mating pairs of adult common South American toad, Rhinella arenarum

weighing approximately 200-250 g were acquired in Lobos (Buenos Aires province, Argentina).

Ovulation of females was induced by means of an intraperitoneal injection of a suspension of 

one homologous hypophysis in 1 mL of AMPHITOX solution (AS) per female. Oocytes were 

fertilized in vitro using fresh sperm suspended in AS. Oocytes were fertilized in vitro using fresh 

sperm suspended in AS. After jelly coat removal, embryos were kept in AS and maintained at 20 

± 2 °C. The AS was replaced entirely every three days and monitored weekly to ensure that the 

pH was at acceptable levels (7 ± 0.5). 

For treatments during embryonic stages (S4-S25), ten embryos were randomly placed in 

triplicate in 10 cm diameter glass Petri dishes containing 40 mL of test solution. For treatments 

during prometamorphosis (S28), ten larvae were placed in triplicate in 20 cm-diameter glass. 

Petri dishes containing 100 mL of test solution. Test solutions were entirely replaced every 48 h. 

Test groups included: 

l) Continuous exposure from early blastula (S4) up to complete operculum stage (S25); 336 h (14 

days) at concentrations between 5 and 30 mg/L. 

2) Continuous exposure from early complete operculum stage (S25) up to late complete 

operculum stage (S25); 336 h (14 days) at concentrations between 1 and 30 mg/L. 

3) Continuous exposure from completed back legs (S28) until completion of metamorphosis; 

1080 h (45 days) at concentrations between 1 and 30 mg/L. 

4) 24 h pulse-exposure with concentrations ranging between 1 and 40 mg/L in blastula (S4), 

neural plate (S13), muscular activity (S18), gill circulation (S20), opercular folds (S23), and 

complete operculum (S25). After the treatments, the embryos were thoroughly washed and 

kept in AS until 168 h post-exposure. 

Toxicity tests were performed using technical-grade atrazine with a purity of 98 %, purchased 

from Chem Service (West Chester, PA, USA). Due to precipitation of atrazine at higher test 

concentrations, 0.2% acetone was added to the test concentrations. Solvent and blank controls 

were maintained. 
Results: At the blastula stage, sublethal effects were noted in atrazine concentrations over 5 

mg/L. Malformations were observed from 48 hours onward and percent affected increased with 

dose, up to 67% at 30 mg/L. The main malformations were: delayed development, reduced 

body size, tail and axial flexures, irregular border, different types of edema, wavy tail, 

microcephaly, malformed mouth and adhesive structures, gut miscoiling, underdeveloped gills, 

cloacal protrusion, and cellular dissociation. 

During short-term chronic (168 h) exposure, the NOEC value for sublethal effects was 10 mg/L. 

The percentage of affected embryos was proportional to atrazine concentration, with a maximal 

of 50 % affected at 30 mg/L. From 96 hour onwards, malformations, mainly tail, axial flexures, 

different types of edema, malformed mouth and adhesive structures, and cellular dissociation in 

specific regions such as the stunted tail, were observed. In acute exposure, treated larvae 

showed neurotoxic effects such as spasmodic contractions and general weakness at 

concentrations equal or higher than 15 mg/L. A reduction in food intake was also observed. 

Lethality was recorded at concentrations higher than 20 mg/L starting from 72 h of exposure 

onwards. 

For the 24 hour pulse exposure, lethality in embryos occurred at 40 mg/L 168 hours post 

exposure. A range of sublethal teratogenic and neurotoxic effects occurred with LOAECs ranging 

from 15 to >40 mg/L, with the blastula stage being the most sensitive and showing the widest 

range of effects. 

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 the potential for teratogenic and 

neurotoxic effects due to atrazine exposure during embryo-larval development. 

Limitations of the Study: Wild caught test animals were used for sources of eggs with unknown 

exposure history. 

Author reported that measured concentrations were within 5% of nominal concentration but no 

measured concentrations were reported or the frequency of measurement. Some 

concentrations exceed the water solubility of atrazine (30 mg/L). 

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 17:57:16 -04'00'