Contaminants of emerging concern


Contaminants of Emerging Concern is a term used by water quality professionals to describe pollutants that have been detected in water bodies, 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 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.

General problem

For a compound to be recognized as an emerging contaminant it has to meet at least two requirements:
  1. Somewhere in the world people are hampered by the effect of the compound.
  2. There is an established relationship between the positive and negative effect of the compound.
These contaminants were not previously detected by systems which analyze water quality, or they were found in much smaller concentrations. They are of emerging concern because we do not yet fully understand the risk they pose to human or environmental health.

Hamperings

Somewhere in the world

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. The same is true for air "soluble" gasses like carbon dioxide: they dissolve in the vast quantity of the atmosphere, and accumulate over time. Emerging Contaminants pose a danger through drinking water as well as air, the Environmental Protection Agency began researching vapor intrusion in the context of emerging contamination in the past years. Vapor Intrusion occurs when contaminants which are subsurface are vaporized, allowing them to enter into public buildings and homes. VI poses a danger to individuals through worsening indoor air quality as well as near-term safety hazards.

Relation between the 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.

Selected compounds listed as emerging contaminants

Table 1 is a summary of data on the twelve emerging contaminants currently listed on one EPA website regarding federal government facilities. EPA published a fact sheet about each contaminant which has been summarized in three categories below.
CompoundUsesWhere it is FoundHealth Risks
Trichloropropane 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 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 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 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 and Perfluorooctanoic acid 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 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 classified as likely carcinogenic, neurotoxic, and thyroid, liver, and kidney toxicity as well as an endocrine disruptor
Polybrominated diphenyl ethers 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 and may be found in dangerous quantities in water sourcesMay cause respiratory complications, and investigated as a potential carcinogen by the CDC

Examples from the Past

There have always been, and will likely always be emerging contaminants in our water supplies, because the list is ever-evolving and many compounds that are intensely regulated now due to their harmful nature were in food, water, and the environment casually in the past.
Emerging contaminants are most often addressed as a hampering in issues 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 on the federal level are primarily responsible for determining standards and statutes which guide policy and control in the state to prevent citizens and the environment from being exposed to harmful compounds. Emerging Contaminants are examples of instances in which regulation did not do what it was supposed to, and communities have been left vulnerable to the adverse health effects of ECs. Many states have assessed what can be done about emerging contaminants and currently view it as a serious issue, but only eight states have specific risk management programs addressing emerging contaminants.

Solutions

For some emerging contaminants, the EPA has suggested that the best control for them is through advancing technology at treatment plants. One suggestion is "enhanced coagulation" in which the treatment entity would work to optimize filtration by removing precursors to contamination through treatment. In the case of THMs, this meant lowering the pH, increasing the feed rate of coagulants, and encouraging domestic systems to operate with activated carbon filters and apparatuses that can perform reverse osmosis. Although these methods are effective, they are costly, and there have been many instances of treatment plants being resistant to pay for the removal of pollution, especially if it wasn't created in the water treatment process as many EC's occur from runoff, past pollution sources, and personal care products. It is also difficult to incentivize states to have their own policies surrounding contamination because it can be burdensome for states to pay for screening and prevention processes. There is also an element of environmental injustice, in that lower income communities with less purchasing and political power cannot buy their own system for filtration, and are regularly exposed to harmful compounds in drinking water and food.