View Poster: PCB Measurements and Risk
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Table: Methods to measure PCBs
There are two methods to measure PCBs in water: EPA Method 608 and Method 1668. Only method 608 is approved by EPA for permit compliance purposes, meaning this will be the method used to measure PCBs in effluent throughout the state. The following sections explain each row of this table.
Both Method 608 and 1668 are considered highly sensitive methods, meaning that they can measure very low concentrations of PCBs. Methods 608 and 1668 can measure PCBs at lower levels than most other chemicals and associated methods. Even though we often think of method 608 being less sensitive than method 1668, in the scheme of water sample testing, the minimum level we can detect PCBs is very good.
This is the method detection limit in water with no other interferences. In a perfect world, PCBs could be measured to these levels. However, in water sampling there are often other things in the water that can interfere with the ability to measure PCBs at the minimum detection limit. These things can include dissolved organic matter, particulate organic matter, calcium, iron, magnesium, sodium, sulfates, and chlorides.
Blanks are used to ensure that the amount of chemical reported from a water sample is from the river/stream it was taken from, and not from glassware/instrument/sampling devices used to process the water sample. PCBs are everywhere including ultrafiltered water and laboratory blanks. Because method 1668 measures PCBs at such low levels it can be difficult to say for certain the level of PCBs dectected is from the the river not from the blank.
Method 608 is approved by EPA for permit compliance purposes. Method 1668 is not approved for permit compliance but can be used to determine sources of PCBs at much lower levels than method 608.
Why are PCBs difficult to Measure?
PCB regulations require PCBs to be measured at extremely low levels. Identifying different sources of PCBs in the environment is difficult because there are many sources and PCBs are found everywhere. Sources of PCBs depend on the characteristics of the environment, human uses and populations, climate, contaminated sites, and history of land use. Because PCBs are everywhere, they are also found in the laboratory equipment and liquids that are used to measure amounts in water samples. Blank censoring is used to account for background PCBs that are added through processing samples in the laboratory, using sampling equipment, and contamination through the environment. Blank censoring subtracts the amount of PCBs added during sample processing from what is reported in the water sample.
Table: Protection levels for PCB exposures
There are two designated uses we protect in Washington for PCBs, including aquatic life and human health. The human health use protects humans for toxic effects of PCBs when consuming fish. The human health criteria states that total PCB levels should be below 7 ppq to be protective of human health. The aquatic life use protects living organisms in surface waters from toxic effects on survival, growth, and reproduction. Aquatic life is protected when PCB level exposures over a short period is 2,000,000 ppq or less and for longer exposures 14,000 ppq.
Levels of PCBs in water quality standards implemented under the Clean Water Act are much more stringent than PCBs allowed in consumer products under the Toxic Substance Control Act. PCBs allowed in consumer products can eventually make it to surface waters and influence compliance with the water quality standards. Note: PCB-11 has a maximum allowable level of 250,000,000,000 ppq in consumer products.
Graphic: Movement of PCBs in the environment
There are several sources of PCBs (products, waste, runoff, discharge) that ultimately end up in rivers and streams. PCBs have a tendency to attach to organic materials so they are often found in sediments or animal tissues at higher levels than in the water. This is because PCBs have limited ability to dissolve in water due to their chemical structure. PCBs are taken up by small animals and plants on the river bottom and through exposure in water. These small animals serve as food for larger animals such as fish. Animals eat other animals and PCBs build up in tissues. As larger animals eat smaller animals, PCBs amounts get higher in the bigger animals.