Limitations of chemical monitoring hinder aquatic risk evaluations on the macroscale

Macroscale evaluations of chemical monitoring data require the integration of chemical, spatial, and temporal dimensions. Here, we linked 64 million US surface water monitoring records (1900 chemicals, date range 1958 to 2019, 310,000 sites) and 37 million analytical limits and in vivo and in silico toxicity thresholds. We found that the exposure data required for retrospective risk assessment were available for less than 1% of chemicals with potential environmental concern ( n ≈ 297,000). In contrast to the situation with persistent and often inorganic contaminants in the 1970s, current monitoring schemes lack control of a much larger number of organic chemicals and their degradates. Insufficient chemical and spatial coverage of monitoring, along with analytical limits being far too high to track some of the most toxic chemicals, biases risk perceptions for important chemicals.