Compound Classes


Several compound classes were analyzed in this study. A brief description of each is provided here to give an overview of what type of contaminants are in each class, potential sources of each class, and documented effects of some of these contaminants.


Anthropogenic Organic Compounds


Anthropogenic organic compounds are a broad suite of compounds that are typically associated with human, industrial, and agricultural wastewater and include detergent metabolites, flame retardants, personal care products, pesticides, plasticizers, PAHs, steroids, and other miscellaneous compounds. Although these compounds are associated with wastewater, it is important to note that the WWTP is not the source of these compounds, but simply a pathway by which these compounds can reach the ecosystem from urban environments. 


Besides WWTP effluent, these compounds also can reach streams from runoff from land applications, industrial facilities, animal feed lots, and septic systems. In 1999–2000, 139 streams were sampled in 30 states across the United States, and AOCs were detected in 80 percent of the streams sampled with as many as 38 compounds in one sample (Kolpin and others, 2002). Some of these compounds bioaccumulate in biota and many are suspected or known endocrine disruptors, meaning they mimic hormones and can cause problems with the endocrine system, which affects reproduction and growth. Detergent metabolites nonylphenol and fragrances like tonalide and galaxolide have been shown to cause endocrine issues in fish (Schreurs and others, 2004), and the antimicrobial disinfectant triclosan can result in reduced algal diversity (Wilson and others, 2003) and increases antibiotic resistance (Sprague and Battaglin, 2005). 


Pharmaceuticals


More than 3.9 billion prescription drugs are purchased annually in the United States, and the average American takes more than 12 prescription drugs each year (Kaiser Family Foundation, 2010). Fifty to 90 percent of the active ingredients in these pharmaceuticals passes through the body and is excreted as either the parent compound or its metabolites (Lubliner and others, 2008). From there, these pharmaceuticals enter the wastewater stream, to either a WWTP or a septic system. Besides excretion, the other main path to the environment for pharmaceuticals is disposal. It was once recommended that consumers dispose of pharmaceuticals through either their drain or toilet, but this outdated practice is now discouraged in an effort to reduce the amount of these compounds travelling to the WWTP. Many states are trying to develop drug take-back programs, but federal narcotic regulations complicate the process. In the meantime, consumers are asked to mix unused pharmaceuticals with coffee grounds or kitty litter and dispose of them in the trash. 


Residential homes, long-term care facilities, health‑care facilities such as hospitals, and veterinary clinics are current sources for pharmaceuticals reaching the environment (Hubbard, 2007), but landfill leachates and garbage-incinerator emissions may be emerging sources as society tries to deal with the disposal issue. Most of these sources use WWTPs as the pathway for reaching the receiving waters. Removal of this class of compounds from the waste stream is complicated by the varying chemical nature of the compounds. Typical treatment techniques used by WWTPs remove some of these pharmaceuticals but are ineffective on others, such as carbamazepine. The amount of pharmaceuticals entering the environment may be reduced by consumers who use fewer pharmaceuticals or select “greener” options (Lubick, 2010), and by proper disposal of pharmaceuticals.


Pharmaceuticals, by intent, are biologically active, therefore, although their exact effects on wildlife are not yet fully documented, their presence in the environment would be expected to have adverse ecological effects (Williams, 2005). Pharmaceuticals and other contaminants delivered through WWTP effluent can be considered to have “pseudo-persistence” because of the continual input of these compounds (Smital, 2008). The effects of continuous low‑level exposure to these pharmaceuticals, particularly during sensitive life stages, as well as long-term exposure to the complex mixtures in these effluents are further unknowns (Daughton and Ternes, 1999). 


Halogenated Compounds


Polybrominated diphenyl ethers (PBDEs) are man‑made chemicals used as flame retardants in electronics, building materials, seat cushions, and clothing. PCBs are stable, nonflammable chemicals used as insulators and cooling compounds in electric equipment and have been used in other products like paint, inks, and pesticides. PCBs and PBDEs have similar structures and are similar toxicologically, causing problems in marine and freshwater fish ranging from neurotoxicity to hormone disruption (Lower Columbia River Estuary Partnership, 2007). A recent study found that exposure to PBDEs was associated with depressed levels of thyroid-stimulating hormone in pregnant women, the health implications of which are unknown (Chevrier and others, 2010). Both PCBs and PBDES are persistent, hydrophobic compounds that do not degrade or dissolve readily in water and tend to bioaccumulate in fatty tissues and have been detected in soil, air, water, sediment, and bodies of fish, wildlife, and people. Johnson and others (2007) measured PCBs in the tissue of juvenile salmon from the lower Columbia River downstream of the industrial and urban Portland/Vancouver area at concentrations exceeding adverse‑effects thresholds. Recently, PBDEs have been detected in multiple arctic species (Arctic Monitoring and Assessment Programme and Arctic Council Action Plan to Eliminate Pollution of the Arctic, 2005), illustrating the ubiquitous nature of these halogenated compounds.


Currently Used Pesticides


Currently used pesticides include herbicides and insecticides that often can be found in any home or garage and are used for pest control (flea medicine for pets often contains fipronil), garden care (household insect spray often contains pyrethroids such as permethrin), or general weed maintenance (Casoron^® contains dichlobenil and Pendulum^® contains pendimethalin). Although pesticides often are discussed as a pollutant of concern in agricultural areas, urban areas can be a source as well because of residential use, commercial‑landscape use, and road maintenance. 


Organophosphates and carbamates have been shown to have sublethal effects on salmon, causing problems with olfaction, homing, and predator avoidance (Sandahl and others, 2007). Pesticides are rarely detected alone and often occur in the environment in mixtures. Mixtures of pesticides can have an additive or synergistic effect when they are together in the environment (Lower Columbia River Estuary Partnership, 2007). Laetz and others (2009) determined that mixtures of diazinon, chlorpyrifos, malathion, carbaryl, and carbofuran—the most extensively used pesticides in California and the Pacific Northwest—significantly inhibit acetylcholinesterase activity more when they are present together than when they are present individually. This acetylcholinesterase inhibition can interfere with survival behaviors and essential reactions to stimuli; therefore, the presence of these mixtures may be affecting salmon recovery more than expected. 


Polycyclic Aromatic Hydrocarbons


PAHs are persistent, widespread organic contaminants that are in petroleum products, creosote-treated wood, paints and dyes, or are created through incomplete combustion (Lower Columbia River Estuary Partnership, 2007). PAHs tend to adsorb to sediments, which can then act as reservoirs for future transport. Benthic invertebrates living in this sediment can bioaccumulate PAHs and pass them on to their predators. In vertebrates, like fish, however, PAHs do not bioaccumulate but are metabolized, and some PAHs are known or suspected carcinogens for vertebrates (Johnson and others, 2002). Parking lots treated with coal-tar-based sealcoat have been shown to be a major source of PAHs (VanMetre and others, 2009); therefore, stormwater passing over these surfaces can transport PAHs to the receiving streams. 


Trace Elements and Mercury


Trace elements are metals and other natural chemicals that can be toxic even at low concentrations and aquatic biota have little need for them. For this report, these compounds include arsenic, cadmium, chromium, copper, lead, nickel, selenium, silver, and zinc. Although trace elements are naturally occurring, they also can be introduced through industrial uses and motor vehicles. For instance, copper and zinc are contributed to roads and other impervious services from brake pads, tires, and vehicle exhaust (Davis and others, 2001), and then stormwater runoff transports these deposits to its receiving waters (Sandahl and others, 2007). Copper has been shown to have sublethal effects on salmon behavior through effects on olfaction even at water concentrations as low as 2 µg/L (Baldwin and others, 2003). Another commonly detected trace element, cadmium, bioaccumulates in reproductive organs of fish and disrupts important endocrine processes, especially those involved in synthesis, release and metabolism of hormones (Tilton and others, 2003). 


Mercury in the environment is never destroyed but simply cycles between chemical and physical forms. In the aquatic environment, mercury is converted to a more toxic form, methylmercury, which is most often detected in fish. Methylmercury is a known neurotoxin and studies have shown that environmentally realistic concentrations of methylmercury can impair the reproductive cycle in fish (Drevnick and Sandheinrich, 2003). 


First posted April 25, 2012