Addressing Data Quality Issues in the Development of a PCB TMDL
Abstract:Polychlorinated biphenyls (PCBs) are persistent, bioaccumulative, toxic pollutants that have caused water quality impairments in a number of water bodies in the United States. More than 1.5 billion pounds of PCBs were manufactured in the United States before their manufacture and general use was almost completely banned by the EPA in the late 1970s. PCBs were used in a wide variety of applications, and are found, at low levels, in the soil, water, sediments and air throughout the continent, and are present at levels above some water quality standards in the open ocean.
Water quality standards for the total of 209 PCB congeners can be as low as 7.9 picograms per liter (pg/l), while EPA's best analytical method for quantifying PCBs, EPA Method 1668A, has stated detection limits that range from 4 to 455 pg/l and reporting limits that range from 10 to 1,000 pg/l for individual congeners. EPA Method 1668A is currently the best available technology for quantifying low levels of PCBs in the environment, however, it has not been validated and approved the EPA. The method effectively separates roughly 160 of the 209 PCB congeners, and was developed with the specific intent of quantifying PCB congeners that EPA felt had the most significant environmental. The analytical method is believed by many experts to be capable of accurately quantifying PCBs at concentrations at least an order of magnitude below the EPA stated reporting limits; however, the cost of analysis, the uncertainty of the measurements, and the impacts of the ubiquitous presence of PCBs in the field and lab environment increases as the reporting level is pushed downward.
The TMDL (Total Maximum Daily Load) process determines the maximum loading of a pollutant that can be assimilated by a water body, and outlines a strategy for reducing the quantity of the pollutant that is entering the water body. Developing a TMDL for PCBs is problematic, in that the applicable water quality standards may be several orders of magnitude lower than can be accurately sampled and measured using the best available techniques. Because the goal of the TMDL process is to reduce impacts to the water body, the environment and the food chain, it is important to develop strategies and tools that will allow less than ideal data to be used to make good decisions.
This paper discusses the impact of data quality on the development of the Stage 1 PCB TMDL for the Delaware River Estuary, and work that is ongoing to improve the quality of the data that will be collected and used for decision making in Stage 2 of the TMDL. Collected data is intended to accurately characterize the loadings, pathways, and ambient concentrations of a given pollutant so that:
Determinations can be made as to significant sources of PCBs to the environment and identification of banks of PCBs in the environment.
Data is collected that is suitable for use in models and other scientific tools that may be used to understand fate and transport of PCBs.
Techniques are identified to ensure that progress can be measured as the TMDL process reduces the ambient concentrations of PCBs in each media.
Document Type: Research Article
Publication date: January 1, 2004
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