RTgill-W1 assay detects pulp and paper mill effluent toxicity

Area of Science:

• Environmental Toxicology
• In Vitro Toxicology
• Cell-Based Assays

Background:

• The development of New Approach Methods (NAMs) is crucial for reducing and replacing animal use in toxicity testing.
• Whole-effluent toxicity testing, particularly the rainbow trout acute lethality test, is a regulatory standard but involves significant animal use.
• The RTgill-W1 assay, a cell line derived from rainbow trout gills, presents a potential in vitro alternative.

Purpose of the Study:

• To evaluate the efficacy of the RTgill-W1 assay as a replacement for the rainbow trout acute lethality test in assessing pulp and paper mill effluent toxicity.
• To compare the toxicity results obtained from the RTgill-W1 assay with those from the traditional rainbow trout acute lethality test.
• To investigate the influence of effluent characteristics on the performance of the RTgill-W1 assay.

Main Methods:

• Collected and prepared 70 pulp and paper mill effluent samples from multiple mills and sampling locations.
• Assessed effluent toxicity using both the rainbow trout acute lethality test and the RTgill-W1 assay with alamarBlue endpoint.
• Analyzed correlations between the two testing methods and investigated the impact of effluent filtration and specific chemical constituents like ammonia (NH3).

Main Results:

• A strong positive correlation (r=0.786, p<0.001) was observed between the RTgill-W1 assay and the rainbow trout acute lethality test for effluents causing significant mortality/cell viability decline.
• The alamarBlue endpoint in the RTgill-W1 assay demonstrated increased sensitivity with filtered effluents (p<0.001).
• Effluent matrix composition did not significantly affect test outcomes, although ammonia exposure induced cellular vacuolation.

Conclusions:

• The RTgill-W1 assay is a promising alternative to the rainbow trout acute lethality test for evaluating pulp and paper mill effluents.
• The assay provides reliable and comparable toxicity data, supporting its potential implementation in regulatory frameworks.
• Further validation could facilitate the adoption of this in vitro method, contributing to animal welfare and efficient toxicity assessment.