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News reports discussing microplastics and how researchers are constantly finding them in new places have proliferated in the media in recent years. To put things into perspective, microplastics have now been found all over the globe as well as in our food, water, and air (EPA, 2022; Lim, 2021). It should come as no surprise then that microplastics have been found in various human tissues with examples including intestinal, lung, and placental tissues (Chen et al., 2020; Ragusa et al., 2021; Schwabl et al., 2019). The human health effects of exposure to microplastics are not yet fully understood as research on this topic is still relatively novel and therefore remains limited. Yet, research has shown microplastics to be toxic to various species of animals and current research on the human health effects of microplastic exposure suggest that they have the potential to be toxic to humans in several ways (Prata et al., 2021; Vethaak & Legler, 2021; WHO, 2019).

One group of animals that microplastic toxicity has been well documented in are fish, which is concerning because microplastics are a common pollutant in our rivers and lakes (Chen et al., 2021; De Sa et al., 2018; Galafassi et al., 2021; Horton & Dixon, 2018; Pannetier et al., 2020; USGS, 2019, Wang et al., 2020; Yang et al., 2021). While the amount of microplastics in the Black Warrior River and its tributaries have not been quantified, there is no question that there are microplastics in the Black Warrior, which is concerning not only for the fish that live in the Black Warrior but also for the many people who rely on and get their drinking water from the Black Warrior and eat fish from it.

Floating litter accumulates in one of Osprey Initiative’s Litter Gitter devices. Image source: https://osprey.world/category/media

The Encyclopedia Britannica (2022) defines microplastics as “small pieces of plastic, less than 5 mm (0.2 inch) in length, that occur in the environment as a consequence of plastic pollution”. Microplastics can then be broken down further into primary microplastics and secondary microplastics based on how they are formed. Primary microplastics are microplastics that are intentionally manufactured to be less than 5 mm in length, while secondary microplastics are microplastics that are formed from larger pieces of plastic pollution that are then broken down into microplastics via any number of environmental processes like erosion or photodegradation (Wang et al., 2021). Examples of primary microplastic sources include cosmetic products, plastic production pellets, and plastic transport vectors for drugs while examples of secondary microplastic sources include broken-down tires, plastic bottles, textiles, and plastic bags (Boucher & Friot, 2017; Kovochich et al., 2021; Sipe et al., 2022; Wang et al., 2021; WHO, 2019). Due to the abundance of plastics in today’s world it is difficult to identify all the potential sources of microplastics that end up in our rivers and lakes. However, some common sources include water runoff from land-based microplastics, effluent discharge from wastewater treatment plants (WWTP) where microplastics from industrial and municipal sources accumulate, sewage overflows, and atmospheric deposition of microplastics (Allen et al., 2019; Kay et al., 2018; WHO, 2019).

Sewage discharges are already an issue for the Black Warrior River whether they are from sewer overflows or one of the numerous WWTPs that discharge their effluent wastewater into the river or its tributaries. This is concerning because recent research by Conley et al. (2019) and Gatidou et al. (2019) has shown that sewage contains high concentrations of microplastics and can be a contributor to microplastics in our waterways. To help address the sewage discharge issue, Black Warrior Riverkeeper monitors the discharge of many of WWTPs on the river to ensure that they are in compliance with their National Pollutant Discharge Elimination System (NPDES) permits, which has been extremely helpful in identifying permit violations and holding these WWTPs accountable. Nevertheless, there is little to nothing that monitoring these WWTPs can do to help address the issue of microplastics potentially being discharged from WWTPs into the Black Warrior. This is because there are currently no state or federal regulations that have established a maximum acceptable concentration of microplastics in our waterways meaning that WWTPs are not required to monitor or remove microplastics from their effluent discharge. Having said that, congress did pass the Microbead-Free Waters Act in 2015 which “prohibits the manufacturing, packaging, and distribution of rinse-off cosmetics containing plastic microbeads” and there was a bill introduced to congress in February of  2020 called the “MICRO Plastics Act of 2020” which, if passed, “directs the Environmental Protection Agency to establish a pilot program that tests the efficacy and cost effectiveness of tools, technologies, and techniques to remove microplastics from the environment, and prevent the release of microplastics into the environment” (FDA, 2022; H.R.5902 – 116th Congress, 2020). It is worth noting that while they represent progress, neither of these bills regulate the concentration of microplastics in our waterways. For more information on sewage in the Black Warrior River and an interactive map of some of the WWTPs visit: https://blackwarriorriver.org/sewage/

These unregulated microplastics are a major issue for the wildlife that lives in and around the Black Warrior River as they are bound to be affected by them. As stated earlier, fish are one of the groups of animals for whom microplastic toxicity has been most well-documented (Chen et al., 2021; Galafassi et al., 2021; Pannetier et al., 2020; Wang et al., 2020). This is largely because rivers, lakes, and fish tissues happen to be some of the places where microplastics accumulate and are found most often (USGS, 2019). Therefore, a significant amount of research has gone into studying the toxicological effects of microplastics on fish, because not only does it help us understand the impact that microplastics have on the environment, but it also allows us to study the mechanisms by which microplastics may be toxic to humans as well (Guerra et al., 2021). Microplastics can bioaccumulate and biomagnify as they move up through the food chain, which can in turn put humans at risk for exposure to high concentrations of microplastics when eating fish (Akhbarizadeh et al., 2019; Cox et al., 2019; Miller et al., 2020; Zhang et al., 2019). Bioaccumulation is the process of a toxicant becoming more concentrated in an organism’s tissues over time as they uptake the toxicant from their environment. Biomagnification is the process by which a toxicant becomes more concentrated in organisms’ tissues as it moves up the food chain (Gray, 2002; Miller et al., 2020; Wang, 2016). Many people fish in the Black Warrior and may rely on the fish they catch for food, so this is particularly concerning for them because while the concentrations of microplastics in the Black Warrior and the fish living in it are unknown, there is a possibility that anytime someone consumes fish from the Black Warrior they are at risk for microplastics exposure.

Image Source: https://mercurypolicy.scripts.mit.edu/blog/?p=499 By Julie van der Hoop

Moving away from the potential human consequences of microplastics in fish, the Black Warrior River is home to a diverse amount of aquatic life including 11 federally endangered species, four of which are fish and include the Cahaba Shiner, the Rush Darter, the Vermillion Darter, and the Watercress Darter. Aside from the Cahaba Shiner, which can also be found in parts of the Cahaba River, these fish can only be found in a few tributaries of the Black Warrior. While no known research has been published on microplastic toxicity in these specific fish species, research on microplastic toxicity in other freshwater fish species have suggested that the mechanisms for microplastic toxicity include their ability to transfer other environmental pollutants into the body, their ability to house and transfer pathogens, their ability to cause physical damage like intestinal blockages, and their ability to induce inflammation and subsequently oxidative stress (Ding et al., 2021; Galafassi et al., 2021; Wang et al., 2020).

Another endangered species that lives in tributaries of the Black Warrior is the Black Warrior Waterdog which is a large salamander that is an indicator species for the river (Bailey & Guyer, n.d.; Curry, 2018; Pillion, 2019). Indicator species are species whose health and status in the environment reflect that of the entire ecosystem, meaning that changes that occur in the indicator species are indicative of changes to come in the entire ecosystem (Britannica, 2019; Siddig et al., 2016). While the Black Warrior Waterdog is most impacted by siltation and sedimentation, there is evidence that microplastics are also toxic to amphibians which could further endanger this species if they are exposed (Boyero et al., 2020; da Costa Araújo et al., 2019). Given the importance of the endangered species living in the Black Warrior, it is clear that we must protect the river from unnecessary contamination by pollutants like microplastics. For more information on the endangered species of the Black Warrior River visit: https://blackwarriorriver.org/endangered-species/

Given the effects that microplastics have on aquatic organisms which can serve as models for the potential toxicological effects that microplastics could have in humans, it is concerning to know that the concentration of microplastics in our waterways are still not regulated. Numerous cities like Birmingham, Cullman, Jasper, Oneonta, Bessemer and Tuscaloosa get their drinking water from the Black Warrior River watershed with Birmingham Water Works, the largest supplier of drinking water in Alabama, getting about half of its water from the Black Warrior watershed (BWWB, n.d.). What this means for the people who get their water from the Black Warrior watershed is that if there are any microplastics in the water that is drawn from the river, there is a possibility that they could end up in drinking water. Similarly to how there are no regulations regarding the concentrations of microplastics in our waterways, there are also currently no regulations here in the U.S. regarding concentrations of microplastics in our drinking water. As a result, public water systems do not have to monitor microplastic concentrations in their drinking water, making it difficult to know for certain whether there are significant concentrations of microplastics in the drinking water coming from the Black Warrior watershed. Studies have shown that microplastics can be found in drinking water, but research on the topic is still relatively limited (Eerkes-Medrano et al., 2019; Kirstein et al., 2021; Li et al., 2020; WHO, 2019). One major limitation regarding the identification of microplastics in our drinking water and waterways is that there is no standardized method for their sampling or identification (Tirkey & Upadhyay, 2021). Therefore, more research needs to be done on the topic so that we can better understand effects that microplastics have on us and our environment, because doing so will allow us to make informed policy decisions regarding microplastics in our drinking water.

While the effects of microplastics on human health are still not fully understood, research has shown that they do negatively affect fish and other aquatic organisms which in turn can negatively affect the environment. Therefore, following the precautionary principle, it is in our best interest to remain wary of microplastics and to do what we can to begin to address the issue now before it becomes any worse. The best thing that individuals can do to begin addressing this issue is to reduce your plastic waste. Some ways to reduce your plastic waste include cutting out single use plastics by using reusable water bottles, grocery bags, straws, and cutlery as well as recycling plastic products when you can, and avoiding any unnecessary plastic products. Some other ways to reduce microplastics include avoiding any cosmetic products that contain microplastics and buying clothes that only use organic fibers like cotton. Also, Black Warrior Riverkeeper hosts cleanups where volunteers remove trash along the river and its tributaries, physically removing one source of microplastics from the river. For more information on volunteering please visit: https://blackwarriorriver.org/volunteer/

Special guest author Samuel Stowe is a graduate student at UAB’s School of Public Health pursuing an MPH. Samuel volunteers for Black Warrior Riverkeeper as a Public Health intern (Summer 2022). 

Black Warrior Riverkeeper and partner organizations organize frequent litter cleanups throughout the Black Warrior River watershed. Photo by Katie Fagan.


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