Dense Nonaqueous Phase Liquids (DNAPLs)Chromium VI
Dense Nonaqueous Phase Liquids (DNAPLs)
1,4-Dioxane
Mercury
MTBE
Perchlorate
POPs
PCBs
TCE
Other Contaminants
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Environmental Occurrence
Most DNAPL compounds are toxic, many are long-lived after release, several bioaccumulate, and some are ubiquitous in the environment—even finding their way to the north and south poles. Trichloroethene, polychlorinated biphenyls, bunker C oil, and chlorobenzene are among the most widely distributed DNAPLs.
Trichloroethene is the most frequently detected organic chemical at Superfund sites and is detected more than any other volatile organic compound at concentrations of concern in ground water and drinking water wells across the nation (Zogorski et al. 2006).
Polychlorinated biphenyls (PCBs) are globally distributed in all environmental media (ATSDR 2002), and they have been found in at least 500 Superfund sites. PCBs are known to bioaccumulate in fish and animals. Several rivers and lakes have been closed to fishing for consumption due to the presence of PCBs in sediment.
Spills of bunker C, a common marine diesel fuel, are a major source of DNAPL contamination on the seas, and bunker C is the largest contributor of the heavy oils released to the environment. Bunker C can coat the sea floor destroying any life it comes in contact with and washes up on beaches where it is a hazard to people and wildlife.
Chlorobenzene, which is used as a solvent and chemical intermediate in industry, has been found in almost every human that has been tested for it in the United States (ATSDR 1990). Chlorobenzene also has been found at 97 Superfund sites.
The wide environmental occurrence of DNAPLs coupled with their persistence in the environment and toxicity makes these compounds a major challenge to public health. Understanding the occurrence and distribution of DNAPLs released to the environment helps investigators locate these compounds, which are difficult to detect and characterize in subsurface environments.
For More Information
The Quality of Our Nation’s Waters: Volatile Organic Compounds in the Nation’s Ground Water and Drinking-Water Supply Wells
Zogorski, John, Janet M. Carter, Tamara Ivahnenko, Wayne W. Lapham, Michael J. Moran, Barbara L. Rowe, Paul J. Squillace, and Patricia L. Toccalino
U.S. Geological Survey, USGS Circular 1292, 2006, 1112 pp
This report summarizes the findings of an investigation of aquifers that supply drinking water to the public. The purpose of the investigation was to determine the presence or absence of 55 volatile organic chemicals in the aquifers.
Toxicological Profile for Chlorobenzene
Agency for Toxic Substances and Disease Registry (ATSDR)
U.S. Department of Health and Human Services, 1990, 100 pp.
This profile covers chlorobenzene health effects, chemical and physical properties, manufacturing volume data, potential human exposure (environmental fate and transport) information, and analytical methods.
Toxicological Profile for Polychlorinated Biphenyls (PCBs)
Agency for Toxic Substances and Disease Registry (ATSDR)
U.S. Department of Health and Human Services, November 2000, 948 pp.
This profile covers PCB health effects, chemical and physical properties, manufacturing volume data, potential human exposure (environmental fate and transport) information, and analytical methods.
TOXNET
The National Library of Medicine
National Institutes of Health
TOXNET is a comprehensive compendium of information on a variety of chemicals, but it is often dated.
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Environmental_Occurrence/
Last updated on Tuesday, June 3, 2008