CADDIS Volume 2: Sources, Stressors & Responses
Unspecified Toxic Chemicals
Ways to Measure Unspecified Toxic Chemicals
Unknown toxic chemicals, by definition, are either unmeasured or inadequately measured; thus, this section may be more accurately titled Ways to Identify Unspecified Toxic Chemicals. Aside from direct measurement for specific chemicals in the environment, related measures may be useful in determining if toxic chemicals should be considered as a candidate cause:
- Presence of chemicals in sediments may suggest that they occurred in the water column in the past.
- Presence of chemicals at low concentrations may suggest that they occur at higher concentrations intermittently.
- Presence of by-products or decomposition products are possible indicators of toxic chemicals.
If tests for toxic chemicals have not been analyzed previously, other types of water analyses may suggest the presence of sources of toxic chemicals. For example, elevated ionic strength or biological oxygen demand may suggest the presence (or historical presence) of an effluent or other source.