There remain some limitations with early life stage toxicity testing. Although ELS tests are quicker and more cost-efficient than full life cycle tests, they remain resource- and time-intensive. Fish early life stage (FELS) tests require hundreds of fish and 1 to 5 months to complete.Villeneuve D, Volz DC, Embry MR, Ankley GT, Belanger SE, Léonard M, Schirmer K, Tanguay R, Truong L, Wehmas L. 2014. Investigating alternatives to the fish early-life stage test: a strategy for discovering and annotating adverse outcome pathways for early fish development. Environ Toxicol Chem 33:158-69. Other issues include the lack of mechanistic information, differing sensitivities between species, and insensitivity to parental exposure. ELS tests don't provide information on the toxicant's mechanism of action. Sensitivity to specific toxicants varies with species, so the most sensitive or most important species should be tested in each case. ELS tests appear to be insensitive to parental exposure, and MATCs are generally the same for embryos of both exposed and unexposed parents. This could be due to the mode of action of the toxicant or the variability and insensitivity of ELS test design. Additionally, growth response has been found to be an insensitive endpoint in ELS tests with fish, having little bearing on the estimation of an MATC.Woltering DM. 1984. The growth response in fish chronic and early life stage toxicity tests: A critical review. Aquat Toxicol 5:1–21. Growth response could be omitted to reduce the duration and cost of screening tests.
