Open Literature Review Summary

Female white leghorn chickens were exposed to diazinon via the diet at concentrations of 0.1, 1.0 and 10.0 ppm. Separate birds were also exposed to malathion at the same test concentrations.Feed was prepared using wettable powders (containing either 4% diazinon or 5% malathion). Each test concentration included 8 individuals. Hens were exposed for a period of 10 weeks. During that time, they were kept in individual laying cages housed within a building with ventilation (temperature 18-31^oC). Hens were fed a commercial breeder ration that did not contain detectable residues of pesticides (specific pesticides included in analysis were not identified). Hens were artificially inseminated by semen pooled from 10 unexposed males twice per week. Prior to exposure, eggs from two hatches were collected to determine fertility and hatchability. Endpoints included egg production, fertility, hatchability, number of chicks hatched per hen (referred to by study authors as “reproductive efficiency”), embryonic mortality and shell thickness. The study author’s results for diazinon, malathion and the controls (during the pesticide exposure period) are provided in the tables below.

This study is considered scientifically valid; however, the results have considerable uncertainties due to the limitations provided below. The results of this study may be used in a weight of evidence approach, however, this study should not be used to derive chronic thresholds or risk quotients.

1. 
   There is uncertainty associated with the nature of the test material due to a limited description. The study indicates that wettable powders containing 4% diazinon and 5% malathion were used; however, the specific formulations were not identified. It is unknown whether or not these formulations are representative of current formulations or would be expected to have an increased toxicity relative to the technical grade active ingredients.
   
2. 
   The control and treatment birds were maintained separate buildings. This calls into question whether the controls were adequate, since they may have been exposed to different conditions compared to the treatments.
   
3. 
   Only 8 replicates were used, which limits the certainty associated with the study results. A higher number of replicates is desired in order to improve the power of the test. For instance, standard avian reproduction studies typically include 16 replicates.
   
4. 
   Because the study authors reported statistically significant effects for all test concentrations, a NOAEC could not be established for diazinon or malathion.
   
5. 
   The statistical method used to determine significance of results was not included in the article.
   
6. 
   The reported results are presented as mean values. The variability associated with the results is not included.
   

1. 
   Only female adult chickens were exposed to pesticides. Impacts of the test material on males and resulting effects to reproduction are not captured in the study design.
   
2. 
   There is uncertainty associated with how representative domesticated chickens are for wild birds. Standard toxicity studies are required for phenotypically wild species; which does not apply to chickens.
   
3. 
   No mention was made of randomization of test birds.
   
4. 
   Since raw data were not provided and variability was not included, reviewer could not confirm study author’s statistical analysis.
   

The reviewer assumed that each treatment included 8 birds. This is based on the study author’s statement that the study included 96 birds to study effects of diazinon, DDT, lindane or malathion. Since each chemical had three separate exposure concentrations, an equal distribution of birds among the treatment groups would result in 8 birds per treatment. The study authors do not indicate how many birds were included in the control.

65887. Brewer S.K., E.E. Little, A.J. DeLonay, S.L. Beauvais, S.B. Jones, M.R. Ellersieck. Behavioral dysfunctions correlate to altered physiology in rainbow trout (Oncorynchus mykiss) exposed to cholinesterase-inhibiting chemicals. 2001. Arch. Environ. Contam. Toxicol. 40, 70-76.

Endangered Species Assessment.

November 19, 2015.