posted on 2024-03-12, 14:36authored byOmar S. Chowdhury, Philip J. Schmidt, William B. Anderson, Monica B. Emelko
Although human health impacts of microplastics are not
well understood,
concern regarding chemical contaminants retained on or within them
is growing. Drinking water providers are increasingly asked about
these risks, but strategies for evaluating them and the extent of
treatment needed to manage them are currently lacking. Microplastics
can potentially induce health effects if the concentration of contaminants
adsorbed to them exceeds predetermined drinking water guidelines (e.g.,
Maximum Contaminant Levels). The risk posed by microplastics due to
adsorbed contaminants is difficult to determine, but a worst-case
scenario can be evaluated by using adsorption capacity. Here, a “Threshold
Microplastics Concentration” (TMC) framework is developed to
evaluate whether waterborne microplastic concentrations can potentially
result in the intake of regulated contaminants on/in microplastics
at levels of human health concern and identify treatment targets for
managing associated health risk. Exceeding the TMC does not indicate
an immediate health risk; it informs the need for detailed risk assessment
or further treatment evaluation to ensure particle removal targets
are achieved. Thus, the TMC concept and framework provide an updateable,
science-based screening tool to determine if there is a need for detailed
risk assessment or treatment modification due to waterborne microplastics
in supplies used for potable water production.