There are no absolute chemical concentrations that correspond to sediment toxicity, but effects range low (ERL) and effects range medium (ERM) values are used as guidelines. The ERM is the concentration of a contaminant that resulted in adverse biological effects in 50% of literature studies evaluated. A more protective indicator of contaminant concentrations is the ERL criterion, which is the concentration of a contaminant above which ecological effects are observed about 10% of the time.

The pie graph shows the proportion of the Delaware Estuary that is good (green), fair (yellow), poor (red) or missing data (blue) for sediment contaminants. The small symbols on the map show the rating at a particular sampling location. To see the measurements made at one of these locations, click on its symbol on the map.