Federal Water Pollution Control Act of 1972
required criteria to be determined for many chemicals.
These are published in the EPA Redbook.
Very little is known about the chronic (long
term) effects of low levels of contaminants
and few organisms have been tested
Testing is complex. Mixtures of chemicals,
habitat, point in life cycle, concentration,
exposure time, manner sediments release
all effect toxicity.
Acute toxicity testing usually measures the
concentration level that kills 50% of
the organisms in 96 hrs. for fish or 48 hrs. for invertebrates.
Chronic toxicity testing may measure reproduction,