contaminants of emerging concern contaminants of emerging concern contaminants of emerging concern (cecs) is a term used by water quality professionals to describe pollutants that have been detected in environmental monitoring samples, that may cause ecological or human health impacts, and typically are not regulated under current environmental laws. sources of these pollutants include agriculture, urban runoff and ordinary household products (such as soaps and disinfectants) and pharmaceuticals that are disposed to sewage treatment plants and subsequently discharged to surface waters. examples of emerging contaminants are 1,4-dioxane, food additives, pharmaceuticals, and natural & synthetic hormones. cecs have the ability to enter the water cycle after being discharged as waste through the process of runoff making its way into rivers, directly through effluent discharge, or by the process of seepage and infiltration into the water table, eventually entering the public water supply system. emerging contaminants are known to cause endocrine disrupting activity and other toxic mechanisms, some are recognized as known carcinogens by the united states environmental protection agency (epa). general problem for a compound to be recognized as an emerging contaminant it has to meet at least two requirements: adverse human health effects have been associated with a compound. there is an established relationship between the positive and negative effect(s) of the compound. emerging contaminants are those which have not previously been detected through water quality analysis, or have been found in small concentrations with uncertainty as to their effects. the risk they pose to human or environmental health is not fully understood. contaminant classes contaminants of emerging concern (cecs) can be broadly classed into several categories of chemicals such as pharmaceuticals and personal care products, cyanotoxins, nanoparticles, and flame retardants, among others. however, these classifications are constantly changing as new contaminants (or effects) are discovered and emerging contaminants from past years become less of a priority. these contaminants can generally be categorized as truly "new" contaminants that have only recently been discovered and researched, contaminants that were known about but their environmental effects were not fully understood, or "old" contaminants that have new information arising regarding their risks. pharmaceuticals pharmaceuticals are gaining more attention as cecs because of their continual introduction into the environment and their general lack of regulation. these compounds are often present at low concentrations in water bodies and little is currently known about their environmental and health effects from chronic exposure; pharmaceuticals are only now becoming a focus in toxicology due to improved analytical techniques that allow very low concentrations to be detected. there are several sources of pharmaceuticals in the environment, including most prominently effluent from sewage treatment plants, aquaculture and agricultural runoff. cyanotoxins the growth of cyanobacterial blooms has been increasing due to the eutrophication (or increase in nutrient levels) of surface waters around the world. the increase in nutrients such as nitrogen and phosphorus has been linked to fertilizer runoff from agricultural fields and the use of products such as detergents in urban spaces. these blooms can release toxins that can decrease water quality and are a risk to human and wildlife health. additionally, there is a lack of regulations regarding the maximum contaminant levels (mcl) allowed in drinking water sources. cyanotoxins can have both acute and chronic toxic effects, and there are often many consequences for the health of the environment where these occur as well. industrial chemicals industrial chemicals from various industries are known to produce harmful chemicals that are known to cause harm to human health and the environment. common industrial chemicals like 1,4-dioxanes, perfluorooctane sulfonate (pfos) and perfluorooctanoic acid (pfoa) are commonly found in various water sources. adverse human health effects due to the large differences in transportability of compounds, there is a great level of variance contaminant to contaminant between the location of contamination and the place of occurring hazards. an example of the a contaminant which can have detected hazards at the point of origin is the effect of municipal solid waste on the environment through seepage and particulate pollution. on the other hand, the effects of water-soluble contaminants may be obscured a long time as they are washed far away from the contamination site and only slowly accumulate in oceans and groundwater to harmful concentrations. relation between compound and effects there is an overlap of many anthropogenically sourced chemicals that humans are exposed to regularly. this makes it difficult to attribute negative health causality to a specific, isolated compound. epa manages a contaminant candidate list to review substances that may need to be controlled in public water systems. epa has also listed twelve contaminants of emerging concern at federal facilities, with ranging origins, health effects, and means of exposure. the twelve listed contaminants are as follows: trichloropropane (tcp), dioxane, trinitrotoluene (tnt), dinitrotoluene, hexahydro-trinitro-triazane (rdx), n-nitroso-dimethylamine (ndma), perchlorate, polybrominated biphenyls (pbbs), tungsten, polybrominated diphenyl ethers (pbdes) and nanomaterials. selected compounds listed as emerging contaminants the norman network enhances the exchange of information on emerging environmental substances. a suspect list exchange (sle) has been created to allow sharing of the many potential contaminants of emerging concern. the list contains more than 100,000 chemicals. table 1 is a summary of emerging contaminants currently listed on one epa website and a review article. detailed use and health risk of commonly identified cecs are listed in the table below. compounduseswhere it is foundhealth risks trichloropropane (tcp)chemical intermediate, solvent, and cleaning producttcps are denser than water, so they sink to the bottom of aquifers and contaminate them, they also have a low capacity to be absorbed organically and leach into soil or evaporate, contaminating the airconsidered a likely carcinogen by noaa dioxanestabilizer of chlorinated solvents, manufacturing of pet, manufacturing by-productoften at industrial sites, and they move rapidly from soil to groundwater, although it was phased out as part of the montreal protocol it is very resistant to bio-degradation and has been found at over 34 epa sitesrapid disruption of lung, liver, kidney, spleen, colon, and muscle tissue, may be toxic to developing fetuses and is a potential carcinogen trinitrotoluene (tnt)pure explosive, military and underwater blastingmajor contaminant of groundwater and soilslisted as cancer-causing by office of environmental health, may cause carcinoma and bladder papilloma dinitrotolueneintermediate to form tnt, explosivefound in surface water, groundwater, and soil at hazardous waste sites, and may be released into the air as dust or aerosolsconsidered a hepatocarcinogen and may cause ischemic heart disease, hepatobiliary cancer, and urothelial and renal cell cancers hexahydro-trinitro-triazane (rdx)military explosiveexists as particulate matter in the atmosphere, easily leaches into groundwater and aquifers from soil, does not readily evaporate from waterdecreased body weight, kidney and liver damage, possible carcinoma, insomnia, nausea, and tremor nanomaterialsbroad classification of ultrafine particulate matter used in more than 1,800 consumer products and biomedical applicationsreleased as consumer waste or spillage, may be airborne, found in food, or in many diverse industrial processesmay translocate into the circulatory system primarily through the lungs, exposing the body to an accumulation of compounds in the liver, spleen, kidney, and brain n-nitroso-dimethylamine (ndma)formed in the production of antioxidants, additives, softeners, and rocket fuel, and an unintended byproduct of the chlorination of waste and drinking water at treatment facilitiesbroken down quickly when released into the air, but highly mobile when released into soil and will likely leach into groundwater, humans may be exposed by drinking contaminated water, ingesting contaminated food, or using products that contain ndmaprobable carcinogen, evidence of liver damage, reduced function of kidneys and lungs perchloratemanufacturing and combustion of solid rocket propellants, munitions, fireworks, airbag initiators, and flareshighly soluble in water so it can greatly accumulate in groundwater, also accumulates in some food crop leaves and milkeye, skin, and respiratory irritation and in high volumes corrosion. potentially disrupts thyroid hormones perfluoro-octane sulfonate (pfos) and perfluorooctanoic acid (pfoa)used in additives and coatings, non-stick cookware, waterproof clothing, cardboard packaging, wire casing, and resistant tubingduring manufacturing, the compounds were released into the surrounding air, ground, and water, is resistant to typical environmental degradation processes and have been shown to bioaccumulate, found in oceans and arctic, meaning they have a high capacity for transportworld health organization categorized possible carcinogen, may cause high cholesterol, increased liver enzymes, and adverse reproductive and developmental effects polybrominated biphenyls (pbbs)flame retardantdetected in the air, sediments, surface water, fish and other marine animals, they do not dissolve so they are not mobile in water but are volatile and prevalent in the atmosphereclassified by international agency for research on cancer as likely carcinogenic, neurotoxic, and thyroid, liver, and kidney toxicity as well as an endocrine disruptor polybrominated diphenyl ethers (pbdes)flame retardant and used in plastics, furniture, and other household productsenter the environment through emissions, and has been detected in air, sediments, surface water, fish and other marine animalsshown to be an endocrine disruptor as well as carcinogenic, also, may cause neural, liver, pancreatic, and thyroid toxicity tungstena naturally occurring element which exists in various household products and military manufacturingtungsten is water-soluble under certain conditions and may be found in dangerous quantities in water sourcesmay cause respiratory complications, and investigated as a potential carcinogen by the cdc diclofenac anti-inflammatory drug can be found in water treatment plant (wtp) effluents. reported to be found in coastal waters as well in large quantities can cause serious gastrointestinal toxicity. severe ecotoxicity to selected breeds of animals bisphenol a (bpa) industrial plastic production (polycarbonate plastics and epoxy resins) found to accumulate in water treatment plant (wtp) effluents bpa is cytotoxic and mutagenic. it exerts various adverse effects on reproductive, immune, endocrine and nervous systems sulfamethoxazole (smx) antibiotics reported to be found in various freshwater systems common side effects include nausea, vomiting, loss of appetite, and skin rashes. it is a sulfonamide and bacteriostatic carbamazepine anticonvulsant reported to be found in various freshwater systems and wtp effluents. common side effects include nausea and drowsiness. serious side effects may include skin rashes, decreased bone marrow function, suicidal thoughts, or confusion. examples from the past in the 19th and early 20th centuries asbestos was used in many products and in building construction, and was not considered a threat to human health or the environment. deaths and lung problems caused by asbestos were first documented in the early 20th century. the first regulations of the asbestos industry were published in the uk in the 1930s. regulation of asbestos in the us did not occur until the 1980s. in the 1970s there was a serious issue with the water treatment infrastructure of some us states, notably in southern california with water sourced from the sacramento–san joaquin river delta. water was being disinfected for domestic use through chlorine treatment, which was effective for killing microbial contaminants and bacteria, but in some cases, it reacted with runoff chemicals and organic matter to form trihalomethanes (thms). research done in the subsequent years began to suggest the carcinogenic and harmful nature of this category of compounds. epa issued its first standard for thms, applicable to public water systems, in 1979, and more stringent standards in 1998 and 2006. rapid industry changes also make the treatment and regulation of cecs particularly challenging. for instance, the replaced substance (genx), for the recently regulated perfluorooctanoic acid (pfoa), a pfas, had a more detrimental environmental impact, resulting in the subsequently banning of genx as well. hence, there is a pressing need for the treatment and management of cecs to keep up with global trends. risks and regulations further information: water pollution emerging contaminants are most often addressed as an issue concerning water quality. the release of harmful compounds into the environment which find their way into municipal food, water, and homes have a negative externality on social welfare. these contaminants have the capability to travel far from the point-source of their pollution into the environment and accumulate over time to become harmful because they have been left unregulated by federal agencies. these harmful compounds cause damage to environmental and human health, and they are difficult to trace therefore it is challenging to establish who should foot the bill for the damage done by ecs. because these contaminants were not detected or regulated in the past, existing treatment plants are ill-equipped to remove them from domestic water. there are sites with waste that would take hundreds of years to clean up and prevent further seepage and contamination into the water table and surrounding biosphere. in the united states, the environmental regulatory agencies