Other Pollutants
Prince George’s County (the County) tracks other priority pollutants like pathogenic bacteria (Escherichia coli [E. coli]) and polychlorinated biphenyls (PCBs). It also monitors emerging pollutants, which are rarely regulated substances that could be potentially harmful to the environment or public health, like chloride and microplastics.
Bacteria
Certain types of pathogenic bacteria, such as fecal coliform bacteria, act as pollutants when they enter surface waters through contaminated wastewater or runoff from agricultural, urban, or industrial sources. Bacterial pollution, which can lead to waterborne diseases, threatens human health and aquatic life. Fecal coliform bacteria are known to cause illness in humans when ingested through activities like swimming and wading or during consumption of shellfish. The County focuses on monitoring E. coli-a type of fecal coliform bacteria.
The Maryland Department of the Environment (MDE) classifies waterbodies in the state based on the waterbody’s existing conditions and the designated uses for the waterbody. The table below presents Maryland’s thresholds for bacteria impairment for two types of Class 1 waters (i.e., Water Contact Recreation, Fishing, and Protection of Nontidal Warmwater Aquatic Life, including fish [other than trout], agricultural and industrial water supply). For E. coli, MDE lists a waterbody as impaired if the steady-state geometric mean is greater than 126 MPN/100 mL in freshwater (MPN indicates the most likely number of bacteria present in a 100-milliliter portion of the sample). For the enterococci group of bacteria, MDE lists a waterbody as impaired if the steady-state geometric mean exceeds 35 MPN/100 mL for either freshwater or marine/estuarine waters.
Maryland bacteria water quality criteria for Class I waters (COMAR 26.08.02.03-3).
| Indicator | Steady-State Geometric Mean Indicator Densitya | Statistical Threshold Valueb | Waterbody Type |
| E. coli | 126 MPN/100 mL | 410 | Freshwater |
| Enterococci | 35 MPN/100 mL | 130 | Freshwater, Marine/Estuarine |
Notes:
MPN=most probable number; mL=milliliters.
a The geometric mean of samples taken over a 90-day period shall not exceed the steady-state geometric mean values for the given indicator.
b 10% of samples taken over a 90-day period shall not exceed the statistical threshold value.
The County has three watersheds (i.e., Anacostia River, Piscataway Creek, and a portion of the Upper Patuxent River) that have total maximum daily loads (TMDLs) for exceedances in bacteria-related water quality standards. To move forward in meeting these goals, the County supports ongoing programs centered on bacterial source tracking and monitoring, as outlined in the County’s Bacteria TMDL Stormwater Wasteload Allocation (SW-WLA) Watershed Implementation Plan.
Polychlorinated biphenyls (PCBs)
Industries widely used PCBs-a group of commercially manufactured synthetic chemicals in the United States between 1929 and 1979-due to their flame-resistant and insulating properties. Although domestic manufacture, use, importation, and distribution of PCBs was banned by Congress in 1979 under the Toxic Substances Control Act, the widespread use of these compounds resulted in legacy contamination of soils that still release the contamination into waterways today. Because of their special chemical properties, PCBs stay in the environment for a long time and can still be released from these pre-1979 legacy sources. They build up in food chains and can harm humans and wildlife by causing cancer, neurological damage, and endocrine disruption. Consuming contaminated fish is a common pathway of human exposure to PCBs.
TMDLs for PCBs have been established for multiple watersheds in the County, though some TMDLs only address the tidal portions of these watersheds. The 2007 inter-jurisdictional TMDL for PCBs for the tidal portions of the Potomac and Anacostia Rivers established a significant reduction target of over 98 percent for the Maryland segment of the Anacostia watershed, which includes Lower Beaverdam Creek (LBC). One of the most significant sources of ongoing pollutant loading to the Anacostia River is from LBC, which is located in the western portion of the County. Over the past two decades, LBC has been the subject of numerous investigations and monitoring campaigns. Since 2019, the County and MDE have investigated potential sources of PCBs in LBC and its tributaries by collecting and analyzing samples from surface water and sediment. Each sampling event helps the County gain insight into the presence and distribution of PCBs in the county and identify potential sources.
The County developed a PCBs TMDL SW-WLA Watershed Implementation Plan. MDE guidelines for PCBs focus on identifying the sources of PCBs to develop appropriate strategies to reduce the amount of these pollutants entering waterways. The County recognizes that effective PCB reduction requires a long-term commitment to routine and consistent sampling, measurement, analysis, and reporting.
Chloride
Winter deicing of roads and sidewalks, via the use of rock salt (sodium chloride) and brine, results in the excess of chloride flowing into freshwater ecosystems. The subsequent increase in salinity in freshwater can harm aquatic life, negatively impact human health, decrease drinking water quality, and threaten infrastructure. The State of Maryland lists five watersheds in the County as chloride impaired water: the Anacostia River, Mattawoman Creek, Piscataway Creek, Upper Potomac River (tidal), and Upper Patuxent River. The County developed a Winter Deicing and Salt Management Best Practices Plan to monitor the severity of the problem and identify potential control practices. The County monitors conductivity as a stand-in for chloride to evaluate the management of salt application in chloride-impaired watersheds. Monitoring chloride also helps protect drinking water sources for County residents.
To learn more about how the use of road salt is affecting waterways in the state of Maryland and its residents, check out this storymap on road salt.
Trash
Solid trash, particularly plastic waste and other non-biodegradable materials, can significantly degrade surface water quality by obstructing flow, creating stagnant areas, leaching chemicals, contributing to nutrient pollution, introducing microplastics, fostering bacterial growth, degrading the visual aesthetic of waterways, and increasing water treatment costs.
In September 2010, the U.S. Environmental Protection Agency (EPA)-approved the TMDL for trash. To meet the load reductions, the County then developed a trash TMDL implementation plan for the Anacostia River watershed.
The County performed trash assessments between 2000 and 2017 using more than 3,000 digital photographs taken during biological assessments at 834 stream sites. The types of trash observed ranged from paper and small plastic items to shopping carts, tires, discarded building materials, and dislodged corrugated sewer pipes or culverts. The team used a simple rating scale-or “trash score” (TS)-to represent the amount of trash visible in each photograph. The TS for a single site ranged from 0 (no trash) to 12 (abundant or heavy trash).
Microplastics
The global production and disposal of plastics has increased over the past 60 years, with a large amount of plastic waste-19 to 23 million tons-making its way into waterways and coastal systems annually. This widespread plastic pollution poses a significant threat to aquatic environments, impacting the health of ecosystems and the species that rely on them. Microplastics-tiny particles less than 5 millimeters in size-have gained increasing attention due to their persistence, widespread distribution, and potential to harm aquatic organisms. Microplastics originate from the breakdown of larger plastic debris as well as from microbeads in personal care products and synthetic fibers from clothing.
Microplastic contamination in freshwater systems is an emerging concern because stormwater runoff can carry these particles from urban, industrial, and residential areas into rivers, lakes, and reservoirs. This contamination threatens water quality, complicates treatment processes, and poses risks to both wildlife and human health, highlighting the urgent need for effective monitoring and mitigation strategies in stormwater management programs.
In 2025, the County monitored microplastics in the upper reaches of several watersheds to identify potential hotspots and determine the types of plastic waste most often found in the waterways. Field teams collect surface water samples, which they test for microplastics, during biological monitoring site evaluation trips. Findings have the potential to inform the County’s management decisions on limiting the use of certain types of plastics, like polystyrene.
Dashboard Instructions
Features
- Use the filter bar, located at the top right of the screen, to refine data based on water quality constituent(s), subwatershed(s), and year(s) collected. Upon clicking the themed filter box, select one or more option from the drop-down menu. Data displayed in the map and tables will then update based on selection. Please note:
- Filters from multiple themes can be selected at the same time.
- Due to the nature of the datasets, biological and stream monitoring data has been separated from the rest of the water quality constituents and is located in its own filter box (to the right of "Water Quality Constituent(s)).
- Use the vertical menu bar in the upper right of the map to customize the map.
- To view the full menu and descriptions of the icons, click on the Expand icon (double arrows) at the bottom of the vertical menu (the last icon).
- To view the list of symbols and their meanings, click on the Legend icon (bullet points).
- To change the preset view, click on the Bookmarks icon (bookmark).
- To view the different map layers, click on the Layers icon (stacked boxes). Hidden layers will have crossed-out eye icons, whereas visible layers will not have an icon present.
- To change the basemap, click on the Basemap icon (four small squares) and select from the options.
- To move around the map, click and hold the cursor on the map, then drag it to see different areas. To zoom in, double click on area of interest on the map. There are also Zoom in (plus symbol)/Zoom out icons (minus symbol) located at the bottom right of the map.
- To reset the entire dashboard to its preset layers and features, including the map, click the Reset icon (circular arrow) located in the lower right-hand corner of the dashboard.
How to use
The map and tables (dashboard) show all available data for all water quality constituents. To select the constituents discussed above, use the filter bar to click on them. The dashboard should update automatically to show relevant monitoring stations (Station IDs) and data.
To explore the data using the map:
- Zoom in on a monitoring station and click on it.
- A pop up text box will appear showing a data summary for each constituent.
- Use the left/right arrow icons at the top left of the pop up box to scroll through all records. Please note: Arrows are only present when the selected Station ID has data for more than one filtered constituent.
- To zoom in further on the station from the pop up box, click the magnifying glass icon in the top right corner (below the Station ID name).
- Zooming in on the map will also filter the list of Station IDs in the table on the top right of the dashboard to show only those stations visible in the map extent.
To explore the data using the tables:
Click a Station ID in the top table. The bottom tables will update to display all water quality records for that station. Meanwhile, the map will zoom to the location of the monitoring station. To explore data using the map, click the point on the map and follow the above instructions.