Description of Use in Document

Description of Use in Document: Quantitative for behavioral line of evidence in ESA risk assessment.
Rationale for Use: Study appears to be of sufficient quality to characterize behavioral effects (swimming) after exposure to malathion [given that the test material was provided by Cheminova, the reviewer assumed that the impurity profile is known and within current limits].
Limitations of Study:

• 
  Test results are based on nominal concentrations instead of measured which likely overestimates the concentrations that the midges were exposed to during the study.
  
• 
  The survival rate of the control groups were not reported.
  

Primary Reviewer: Amy Blankinship, Chemist, EBR6

Secondary Reviewer:
Open Literature Review Summary
Chemical Name: Malathion,
PC Code: 057701(malathion)
ECOTOX Record Number and Citation:

114293. Laetz CA, Baldwin DH, Collier TK, Hebert V, Stark JD, Scholz NL. 2009 The Synergistic Toxicity of Pesticide Mixtures: Implications for Risk Assessment and the Conservation of Endangered Pacific Salmon. Environ. Health Perspect. 117(3): 348-353

Purpose of Review:

Endangered Species Assessment.

Date of Review:

November 29, 2016.

Summary of Study Findings:
While malathion, diazinon, chlorpyrifos, carbaryl, and carbofuran were tested in this study, this review focuses on malathion.
Methods
Juvenile coho salmon (Oncorhynchus kisutch; 4-7 months old; 4.9±1.0 cm and 1.3±0.9g; eggs obtained from Univ. of Washington and reared at Northwest Fisheriers Science Center) were exposed to several organophosphates (OP) and carbamates (CB) (≥98% purity, Chem Service) individually or in combination for 96-hours under static-renewal conditions. Pesticide stocks were prepared in methanol or ethanol at a concentration of ≤0.0004% of the total volume (100µL aliquot into 25L hatchery water). Eight fish were exposed per treatment and they were not fed during the study. After 96 hours, fish were euthanized and brain tissues were removed and acetylcholinesterase (AChE) activity was measured. In the three mixture exposures where mortality was observed, dead fish were removed after 24 hours and processed as described above. Water samples were collected immediately after addition to tanks and analyzed for pesticide concentration (except for chlorpyrifos where concentrations were not measured, study authors stated prior work indicated stability). Statistical tests included nonlinear regres­sion to fit curves of AChE activities, one-way analysis of variance (ANOVA) followed by Dunnett’s post hoc test to establish differ­ences between groups, and one-sample t-test with a Bonferroni correction.
Results
The measured concentrations of malathion were 89±26% of nominal. No mortality was observed in any of the single chemical exposure concentrations. There was also no statistically significant difference in AChE activity between the unexposed fish and the solvent control fish. Therefore, AChE in the treatment groups were expressed as a percentage of the solvent control. The Log EC50s for AChE inhibition for each of the chemicals in presented in the table below (copied without alteration). For malathion, the inverse of LogEC50 of 1.9 is equal to 79.4 µg/L.


AChE activity for the mixtures of OPs and CBs are presented in the table below (copied without alteration). According to the study authors, all binary pesticide combinations produced toxicity that was either additive or synergistic, with the frequency of synergism increasing at higher exposure concentrations.


Description of Use in Document: Qualitative
Rationale for Use: Study appears to be of sufficient quality to characterize AChE effects after exposure to malathion however, there is uncertainty in the impurity profile of the malathion.
Limitations of Study:

• 
  Test results are based on nominal concentrations instead of measured which likely overestimates the concentrations that the fish were exposed to during the study given that the percent recovery was 89±26% for the single concentration and ranged from 44-91% for the mixture trials.
  
• 
  While analytical grade material was used, there is uncertainty in the impurity profile.
  

Primary Reviewer: Amy Blankinship, Chemist, EBR6

Secondary Reviewer:

1 http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/endangered_species_reregistration_workgroup/esa_evaluation_open_literature.htm#att_6

2 E75127. Hoda Q; Azfer MA; Sinha SP. 1993. Modificatory Effect of Vitamin C and Vitamin B-Complex on Meiotic Inhibition Induced by Organophosphorus Pesticide in Mice Mus musculus. Int. J. Vitam. Nutr. Res. 63(1): 48-51

3 http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/endangered_species_reregistration_workgroup/esa_evaluation_open_literature.htm#att_6

4 All reported concentrations are on an active ingredient basis.

B3 (EC) -

Directory: pesticides -> nas -> final
final -> Appendix 1-10: Summary of Diazinon Monitoring Data
nas -> Description of revision
final -> Appendix 2 Chlorpyrifos Species Sensitivity Distribution Analysis for Fish