Emerging Contaminants Are Getting More Attention

PFAS (perfluorinated compounds) are one kind of emerging contaminant spawning a lot of attention these days.  But there continue to be new stories about others also, and biosolids are often mentioned as a mode by which they get into the environment.  Recent media coverage includes:
Microplastics in organic residuals are examined, following on the increased publicity around macro- and micro-plastics in the aquatic environment. Composts, digestates, and biosolids contain them in different levels and sizes, as discussed in this recent paper out of Germany and this CNN report (don't just watch the video, which provides an important message about source reduction, but also read the story).
Carbon nanotubes lab research at the University of NV Reno.

Articles like these should be viewed with some skepticism, because they continue in the tradition of research that overestimates potential risk by using greenhouse and lab trials using small containers and soils or hydroponic solutions (as in the case of the carbon nanotubes study) spiked with fresh contaminants. In addition, these research efforts involve scientists' ever-increasing analytical abilities to detect traces of anything anywhere - which is excellent, but requires the reminder that the presence of a trace of a contaminant may or may not mean it poses risk. 

Such experiments are useful as one step in figuring out how to advance scientific understanding, but their results should not be interpreted as being representative of how trace contaminants act in aged biosolids from a wastewater treatment process applied in real-world field conditions.  The potential for leaching, run-off, and plant uptake are usually significantly lower than is found in these artificial experiments.