This article is the third in a series of three by Senior Scientist James Markwiese, Ph.D., discussing the quality control and quality assurance measures for state-of-the-practice toxicity testing. The series focuses on mechanisms to facilitate the establishment and documentation of quality procedures for toxicity testing laboratories. The first article in this series is available here. The second article in this series is available here.
To date, we have considered consequences of mischaracterizing (over- or underestimating) the toxicity of a test material (foods, ingredients, raw materials finished products) and the role of laboratory audits in ensuring the quality of toxicity testing results. This final segment will highlight the strengths and weaknesses of toxicity testing to highlight what can be expected regarding the use of toxicity test results for decision making.
Toxicity testing represents a powerful line of evidence for assessing impacts from trace-level chemical contaminants in the test material. Toxicity test results are more realistic than basing conclusions on literature values because they incorporate synergistic, antagonistic, and kinetic features of the particular medium. Additionally, toxicity testing can provide transparent scientific input to decision-makers regarding certainty (vs. uncertainty), importance, and significance of results. For example, literature-based estimates are typically based on exposures to single chemicals. But because contaminated media typically represents a mixture of chemicals, bioassays can integrate effects from multiple stressors using the specific test material being studied.
While there are many benefits from toxicity testing, there are also many hurdles to proper implementation. Shortcomings associated with toxicity testing are myriad and include the following:
- insistence on using only standardized toxicity tests
- conducting testing because it is possible, not because it will provide necessary information/answer the questions that need answering
- endpoints may be limited
- test taxa may not be the same or even similar to those in the real world (different sensitivities)
- failure to apply data quality objectives
Appropriate quality assurance and quality control can also be employed to reduce uncertainty and increase test acceptability.
If you have questions about toxicity testing quality assurance, please contact James Markwiese, Ph.D. at 865.376.7590.