An improved method for calculating toxicity-based pollutant loads: Part 1. Method development

Area of Science:

• Environmental Chemistry
• Ecotoxicology
• Risk Assessment

Background:

• Pollutant loads assess regulatory compliance but often involve mixtures of chemicals with joint toxicity.
• Assessing pollutant loads for ecosystem protection requires considering mixture toxicology principles.

Purpose of the Study:

• To propose an improved method for converting pollutant loads into toxicity-based loads (toxic loads).
• To enhance the accuracy and environmental relevance of toxic load calculations for ecosystem protection.

Main Methods:

• Utilized a modified toxic equivalency factor (TEF) derivation method.
• Employed relative potencies (RePs) of multiple species to represent ecological community response.
• Calculated TEF from a percentile of a cumulative distribution function (CDF) fitted to RePs.

Main Results:

• The improved method allows determination of the optimal CDF percentile for environmentally relevant and robust toxic loads.
• Environmental relevance ensures toxic load reduction correlates with ecosystem health improvement.
• Robustness ensures toxic load calculations are unbiased by the choice of reference chemical.

Conclusions:

• The enhanced methodology ensures environmentally relevant and robust toxic load calculations.
• Accurate toxic load determination supports better environmental management decisions.
• Reduced toxic loads are expected to lead to improved water quality and ecosystem health.