Contaminants of Emerging Concerns

Common Questions

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What are CECs? What is the overall scientific concern? What are the concentrations of these compounds? What are PPCPs? What are the major sources of PPCPs in the environment? Should I be worried about ecological and/or human health? Where are PPCPs found in the environment? What are some major issues with respect to effects of PPCPs? How do I properly dispose of unwanted pharmaceuticals? Why can't I just dump pills into my kitchen trash can? Do I really need to go through all those steps? I have heard that drugs have been detected in liquid seeping from landfills. Why encourage people to put medications in their trash? If I flush medicines down the toilet or pour them down the sink aren't they removed at the wastewater treatment plant?

What are CECs?

Modern science has produced new products and medicines that have improved quality of life; however, their production, use, and disposal have resulted in the presence of low levels of microconstituents in the environment. Microconstituents, also known as Contaminants of Emerging Concern (CECs), are miniscule particles of natural and manmade substances, such as pharmaceutical and personal care products (PPCPs), pesticides, and industrial chemicals, which have been detected within water and the environment. The risk to human health and the environment associated with their presence, frequency of occurrence, or source may not be known; although human health impacts are considered unlikely. Other examples of CECs include nanomaterials, flame retardants, plasticizers and preservatives present in wastewater or agricultural and urban runoff. When specifically sampled in wastewater effluent, CECs are also called Trace Wastewater Constituents.

What is the overall scientific concern?

Many studies have determined that CECs are present in our nation’s waterbodies.  Further research suggests that certain chemicals can cause ecological harm, yet more research is needed to determine the extent.  These contaminants are in the environment at extremely low concentrations and have not been established as causes to human illness, but more research is needed.

Reasons for concern include the unknowns associated with:

  • Large quantities of CECs entering the environment after use by individuals or domestic animals;
  • Municipal sewage treatment plants, which are not equipped to remove some CECs. Effective treatment varies based on the type of chemical and the individual treatment facility;
  • The risks posed to the environment and to humans are unknown, mainly because the concentrations are so low.  Major concern has been over the resistance of antibiotics and disruption of aquatic endocrine systems (the system of glands that produce hormones that help control the body's metabolic activity); and, 
  • The numbers of CECs are increasing. For instance, in addition to antibiotics and steroids, more than 100 individual PPCPs have been identified (as of 2007) in environmental samples and drinking water.

While these compounds may be detected at very low levels in source waters, people regularly consume or expose themselves to products containing these compounds in much higher concentrations through medication, food and beverages and other sources. The level in which they are found in source waters is very small in comparison.

What are the concentrations of these compounds?

Water professionals have the technology today to detect more substances at lower levels than ever before. The CECs have been detected in water resources at parts-per-trillion and parts per-quadrillion levels. Because units of measurement are often difficult to place into context, the following comparisons are provided:

One-Part-Per-Million (mg/L or ppm)

  • one automobile in bumper-to-bumper traffic from Cleveland to San Francisco
  • one inch in 16 miles
  • one minute in two years
  • one ounce in 32 tons
  • one cent in $10,000

One-Part-Per-Billion (ug/L or ppb) = 1/1000 ppm

  • one four-inch hamburger in a chain of hamburgers circling the earth at the equator 2.5 times
  • one silver dollar in a roll of silver dollars stretching from Detroit to Salt Lake City
  • one kernel of corn in a 45-foot high, 16-foot diameter silo
  • one sheet in a roll of toilet paper stretching from New York to London
  • one second of time in 32 years

One-Part-Per-Trillion (ng/L or ppt) = 1/1000 ppb or 1/100,000 ppm

  •  one square foot of floor tile on a kitchen floor the size of Indiana
  • one drop of detergent in enough dishwater to fill a string of railroad tank cars ten miles long
  • one square inch in 250 square miles
  • one mile on a 2-month journey at the speed of light

One Part Per Quadrillion (pg/L or ppq) = 1/1000 ppt or 100,000 ppb or 1,000,000 ppm

  • one postage stamp on a letter the size of California and Oregon
  • one human hair out of all the hair on all the heads of all the people in the world
  • one mile on a journey of 170 light years

What are PPCPs?

Pharmaceuticals and Personal Care Products (PPCPs) as potential pollutants refer to any product used by individuals for personal health or cosmetic reasons and products used by agribusiness to enhance growth or health of livestock. PPCPs are one source of CECs and include a wide range of chemical substances. Pharmaceuticals include prescription and over-the-counter medications for human or animal use. Personal care products may include cosmetics, fragrances, lotions and shampoos.

What are the major sources of PPCPs in the environment?

PPCPs typically enter the environment when passed through or washed off the body and into the ground or sewage system, or when disposed of into the trash or sewage system. Even simple activities such as shaving, using lotions, or taking medication have been attributed to adding chemicals to the environment.  Many of the issues pertaining to the introduction of drugs to the environment from human usage also pertain to veterinary use, especially for antibiotics and steroids.

Sources of PPCPs include:

  • Human activity (e.g., bathing, shaving, swimming),
  • illicit drugs use,
  • veterinary drug use (especially antibiotics and steroids),
  • agribusiness,
  • residues from pharmaceutical manufacturing (well defined and controlled) and
  • residues from hospitals.

People contribute PPCPs to the environment when:

  • Medication residues pass out of the body and into sewer lines,
  • externally-applied drugs and personal care products they use wash down the shower drain and
  • unused or expired medications are discarded into the toilet, sink or even in the trash

Should I be worried about ecological and/or human health?

There is no evidence of adverse human health effects from PPCPs in the environment, due to the extremely low levels of these compounds. Research, however, does indicate that there may be some ecological harm to sensitive species when certain chemicals are present; the United State Environmental Protection Agency (US EPA) may use Federal rulemaking processes to limit certain CECs in the future, as the science develops a better understanding of environmental impacts. While research has not demonstrated human health impacts from these compounds, the ongoing conversation should remind us of how precious our source waters are and the need to protect them.

Where are PPCPs found in the environment?


PPCPs exist wherever people or animals are treated with drugs and use personal care products. PPCPs dissolve easily and don’t evaporate at normal temperature and pressures so are frequently found in aquatic environments influenced by treated sewage, including rivers, streams, groundwater, coastal marine environments, and some water drinking water sources.

The use of municipal and agricultural biosolids as well as reclaimed water for irrigation may also cause PPCPs to come into contact with soil. 

What are some major issues with respect to effects of PPCPs?

Drugs are purposefully designed to interact with cellular receptors at low concentrations to stimulate a biological effect.  However, when PPCPs enter the environment, interaction may occur with unintended targets and cause adverse effects.  Exposure risk for aquatic organisms is of major concern because these organisms are subject to continual exposures, multi-generational exposure, exposure to higher concentrations of PPCPs in untreated water and possible low-dose effects.  In addition, effects may be subtle because PPCPs in the environment occur at such low concentrations.  There is a need for research on subtle effects because they may accumulate and become more significant.

How do I properly dispose of unwanted pharmaceuticals?

According to the Food and Drug Administration, the following steps need to be taken to dispose of unused medication:

  • Follow any specific disposal instructions on the drug label or patient information that accompanies the medication. Do not flush prescription drugs down the toilet unless this information specifically instructs you to do so.
  • If no instructions are given on the drug label and no take-back program is available in your area, throw the drugs in the household trash, but first:
  • Take them out of their original containers and mix them with an undesirable substance, such as used coffee grounds or kitty litter. The medication will be less appealing to children and pets, and unrecognizable to people who may intentionally go through your trash.
  • Put them in a sealable bag, empty can, or other container to prevent the medication from leaking or breaking out of a garbage bag.

Why can't I just dump pills into my kitchen trash can? Do I really need to go through all those steps?

The extra steps provide a safer method for disposing of unused or expired medications.  Unfortunately, when pills are thrown directly into the trash, it can lead to unintended exposure to people or animals.  People may go through the trash to obtain unused medications or personal information found on discarded prescription bottles

I have heard that drugs have been detected in liquid seeping from landfills. Why encourage people to put medications in their trash?

The best option for discarding unwanted/expired household drugs is to bring them to a household drug collection event where collected drugs are properly destroyed via incineration. If a collection event is not available near you, disposal in household trash is preferred over flushing.

Additionally, ask your local pharmacy or local government to host a drug collection event.

If I flush medicines down the toilet or pour them down the sink aren't they removed at the wastewater treatment plant?

New technology is capable of detecting low concentrations of chemical wastes, including small amounts of pharmaceuticals.  Studies show municipal wastewater treatment facilities do not remove some pharmaceutical wastes and/or their by-products.  However; studies show that those trace amounts have no appreciable risk to human health.

US EPA has published the results of an extensive review of the recent literature on wastewater treatment technologies and their ability to remove a number of chemical contaminants of emerging concern (CECs).  US EPA has also made available a computer-searchable format of the data from this literature review.





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