08 • 12 • 2022

Pollution Source Tracking to Protect Public Health at the Beach

By Paula Sternberg Rodríguez

If you were to take a small sample of water from your local beach… Would you know what’s in it? 

While there can be plenty of nutrients and minerals in any given water sample, there are also other substances or organisms that may put your health at risk! Harmful chemicals, bacteria, viruses and other pathogens are often present in our coastal waters and can have a negative impact on our health. It’s estimated that around 90 million recreational water-borne illnesses occur nationwide every year, which combined have a cost of $2.2- $3.7 billion. The good news is that thanks to the BEACH Act of 2000, there are agency-run beach programs as well as volunteer efforts like the Surfrider Foundation’s Blue Water Task Force, which help track contamination levels in our beaches. 

These programs help to detect and measure concentrations of fecal indicator bacteria (FIB), such as enterococcus, as a measure of public health risk in marine water. High FIB concentrations indicate the presence of fecal matter originating from warm-blooded animals in the water along with associated pathogens that can make people sick. However, the testing methods used by most state and local beach programs don’t provide any information on which species is associated with those high FIB concentrations. Although water quality monitoring can tell us if we should or shouldn’t go into coastal waters due to contamination, it doesn’t tell us where the pollution is coming from. So… how do we find out where beach contamination originates from? Allow us to introduce pollution source tracking.

Pollution source tracking is a science developed to tell us what the origin of contamination is so we can find a solution. Pollution source tracking can be done on different contaminants, including chemical compounds, pathogens, and microbes, that can have negative effects on our environments and public health. For these reasons, source tracking can be divided into different categories: microbial source tracking, chemical source tracking, and other source tracking methods. Microbial source tracking uses microbiology and genetic tools, while chemical source tracking uses – you guessed it – chemical compounds as markers to track pollution. Microbial source tracking is great at detecting the specific species responsible for fecal pollution, while chemical source tracking is exclusively used to detect the presence of human domestic wastewater. Other methods include things like dog-sniffing and computer modeling!


Pollution Source Tracking with DNA

All fecal contamination is dangerous to public health and can cause water-borne illnesses, and contamination coming from human poop is oftentimes considered the most dangerous. For these reasons, finding out who the fecal pollution belongs to is super important. Microbial source tracking techniques can help tell if fecal contamination is coming from humans, dogs, birds, cattle, or other animals. Kind of like a fingerprint, animals, humans, and microbes have unique genetic IDs, so if you have a water sample that’s contaminated with feces, you can figure out what species it belongs to through the DNA present in the water sample. Different genetic analysis tools can be used for DNA identification depending on the available budget, goals, and chosen microbial source tracker for the study. 

The most common genetic analysis tools used for microbial source tracking are PCR or “polymerase chain reaction” technologies. Traditional PCR works like a fancy copying machine that takes a specific fragment of DNA and amplifies, or “copies”, it to an amount that can then be identified by scientists. Other PCR technologies like qPCR or “real-time PCR” and ddPCR or “droplet-digital PCR” can count the specific number of nucleic acids (which are the building-blocks for DNA) in a DNA strand. Both provide higher precision and resolution than traditional PCR, but qPCR is more commonly used in source tracking studies as more labs and providers are equipped to run these analyses than ddPCR. PCR technologies can tell us who fecal DNA belongs to. Don’t worry, we don’t mean that these tools can tell us the culprit is Steve from down the street, we just mean we can determine if it’s in fact human-caused or from another animal species. This identification can be done by using genetic markers that are found in host-specific bacteria, bacteriophages, antibiotic resistant genes, and entire microbial communities. Once we know where the fecal contamination is coming from, we can take action to stop it.


Pollution Source Tracking with Chemical Markers

Did you know that DNA isn’t the only helpful marker for pollution source tracking? Ask yourself… What other unique markers are expelled in domestic wastewaters and can assist us in tracking the origin of human contamination? Household chemicals! That’s right – caffeine, sucralose (Splenda), laundry brighteners, synthetic fragrances, and acetaminophen (the active ingredient in Tylenol) are all common household chemicals that can be used for source tracking. Since these chemicals are associated with humans, if one or more are found in a body of water, we can assume the water body has been contaminated with domestic wastewater. 

Chemicals are good source trackers since (unlike microbial source trackers) they’re not alive and can usually last longer in the environment. Most chemicals can be extracted from water samples and their concentrations determined in contaminated water bodies, using lab analyses such as liquid chromatography and mass spectrometry. Some chemicals like acetaminophen that have a shorter “life-span” in the environment can even tell us how recent a contamination event was. This is all useful data that can help us identify where pollution is coming from and inform authorities to take proper action. 


Pollution Source Tracking with Other Methods

Pollution source tracking is a continually developing science and as such, novel methods are constantly popping up. Computer modeling is one of them, and in recent years has proven extremely helpful in determining origins of pollution. Computational models take into account environmental factors that are sometimes missed by chemical or microbial source tracking. The environmental factors can be anything from weather to specific hydrologic variables in a watershed, making machine learning a powerful tool for pollution source tracking. 

Other methods that have proven useful are things like dog sniffing, which is a great way to determine if there is human sewage in a polluted waterway. 


Pinpointing Location of Sources to Fix Pollution Problems

Although source tracking tells us whether fecal contamination is human or other, not all of the methods presented can identify exactly where contamination is originating from. Because of this, additional techniques like sanitary surveys and smoke and dye testing of sewers or wastewater systems have been used to pinpoint exactly who is responsible for fecal contaminants and where they are coming from. Once this information is in-hand, then plans can be made to fix the pollution problems and prevent water contamination events from happening in the future.

Helping local communities identify and fix their sources of pollution is a great way to ensure clean water and healthy beaches and to protect our valuable coastal tourism and recreation economies that support 2.5 million jobs and generate $157 billion in GDP every year. To learn more microbial, chemical and other pollution source tracking methods, check out Surfrider Foundation’s new Beachapedia article: Pollution Source Tracking Technologies.

Learn more about source tracking and real-life studies conducted by Surfrider Chapters across the US, by watching this webinar.