Nevertheless, small amounts of PCBs occasionally enter the system from contaminated runoff or atmospheric deposition. MWRA is limited to discharging 0.000045 micrograms per liter of PCBs measured as Arochlors. This parameter is measured once per month. Toxicity Testing . These tests measure the toxic effects of effluent on standard test organisms.
Acute toxicity ascertains the impact of effluent in creating short-term reversible effects.
The organisms used for this test are mysid shrimp and inland silverside minnows. Chronic toxicity tests measure the long-term and irreversible toxic effects of sewage. Chronic toxicity is measured on the growth of the inland silverside minnow, and by a fertilization test on sea urchins. EPA and DEP created an independent panel of scientists to review monitoring data and advise on key scientific issues related to the permit. The effective date of the permit is August 9, 2000.