The Toxicity of Microplastics Explorer (ToMEx) 2.0

Area of Science:

• Environmental Toxicology
• Ecotoxicology
• Risk Assessment

Background:

• The Toxicity of Microplastics Explorer (ToMEx) database, initially released in 2021, is a crucial open-source resource for microplastic toxicity data.
• Exponential growth in microplastic research literature has rendered the original ToMEx database outdated, necessitating an update.
• The database is vital for hazard characterization and risk assessment within the microplastic research community.

Purpose of the Study:

• To update the ToMEx database by incorporating new toxicity data from peer-reviewed literature using a crowd-sourcing approach.
• To re-evaluate ecological health-based microplastic thresholds using an updated dataset and a previously established framework.
• To assess the impact of the updated data on threshold values and their uncertainty intervals for both freshwater and marine environments.

Main Methods:

• An international crowd-sourcing effort was employed to extract and integrate new microplastic toxicity data into the ToMEx database.
• A framework utilizing species sensitivity distributions was reapplied to derive ecological health-based microplastic thresholds.
• Newly extracted data were screened for minimum criteria to determine suitability for threshold derivation.

Main Results:

• The ToMEx aquatic and human health databases approximately doubled in size, with modest increases in data diversity.
• Most previously observed trends, such as increased toxicity with smaller particle sizes, persisted.
• The updated data enabled the separation of freshwater and marine compartments, revealing significant decreases in marine thresholds when molecular/cellular endpoints were included.
• Thresholds remained wide, and a high percentage of studies (89%) failed screening criteria for threshold derivation, indicating a need for fit-for-purpose data.

Conclusions:

• The updated ToMEx database (ToMEx 2.0) significantly enhances its value for researchers studying microplastic hazards.
• The separation of freshwater and marine data revealed distinct impacts on derived thresholds, particularly for marine environments.
• Despite improvements, the limited number of studies suitable for threshold derivation highlights a critical data gap for environmental managers.
• Future iterations of ToMEx could benefit from AI applications for data curation and toxicological outcome prediction.