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

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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 co ntaining 40 mL of test solution. For treatments during prometamorphosis (S28), ten larvae were pl aced 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 ra nging between 1 and 40 mg/L in blastula (S4), neural plate (S13), muscular activity (S18), g ill 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 stru ctures, 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 proportion al 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 ne urotoxic 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 su fficient quality for inclusion in
risk assessment.

Rationale for Use: The study provides information on the potential for teratogenic and neurotoxic effects due to atrazine expo sure 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 so lubility of atrazine (30 mg/L).

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

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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'