There are known and established standards for different common contaminants in water internationally (WHO) recognized or regionally domesticated WATER standards, but wish to know if there are any for contaminants of emerging concerns (CECs).
I don't know if I clearly got the sens of the question. Generally CEC or cation exchange capacity is analyse as routine parameter in soil samples and not as chemical charateristic of water quality...
There is no single standard applicable for entire class of CECs. You need to find the guideline value (GV) for each CEC from different environmental agencies like USEPA, Canadian, Australian or WHO.
Also there are different GVs for such CECs in drinking water or for aquatic life.
BTW which CECs are you interested in?
There are currently no standards for microplastic testing/research methods.
You can go through this article. May be helpful.
Article Emerging contaminants in wastewater: A critical review on oc...