ABSTRACT
For various reasons , it is somet imes desir able to red uce the c omplex ities of expo sure-re sponse
relationshi ps for v arious taxa, pro cesses, an d other eco logical pro perties to a single num ber
that is presu med to be a suff iciently protect ive level. Those that are us ed to separat e
accepta ble from unaccep table concen trations for regula tory purp oses are termed crite ria or
standar ds (hencef orth, sim ply crit eria). Thos e that are used for screenin g or priori tization are
termed screeni ng bench marks or screeni ng values .
