US EPA

SOURCES:

1. Combustion Sources: This line of research investigates formation and emissions of dioxin-like compounds from industrial combustion sources such as incinerators.
   • Congener Profiles of Combustion Emission Sources: This article describes the derivation and displays congener profiles from several sources of dioxin release.

   • Toxicity Indicators: These studies investigate the possibility that there can be fast and less expensive post-boiler indicators for evaluating TEQ emissions from combustion sources as compared to measuring dioxin-like compounds themselves.
     • PCDD/F TEQ Indicators and Their Mechanistic Implications: This article provides an overview of the theory of toxicity indicators and takes data on 210 PCDD/F isomers from a municipal solid waste incinerator to evaluate some of the lower chlorinated isomers as possible toxicity indicators for overall TEQ.

     • Chlorobenzenes, chlorophenols, PAHs and low chlorinated dioxin/furans: This study takes additional data from a municipal solid waste incinerator and looks at these compounds as possible TEQ indicators.
   • Gas- and Solid-Phase Partitioning of Dioxins on Fly Ash: This study investigated the potential bias in whether dioxins are evaluated as solid-phase or gas-phase in fly ash measurements in an entrained flow reactor.

   • Formation of Dioxins From Soot and Aromatics: This study looked at the role of soot emitted from the combustion flame, in combination with the presence of aromatics (such as benzene and phenol) in the formation of dioxins and furans.

2. Diesel Emissions: This study measured the emissions of dioxins from a diesel truck while the truck was driven in normal road conditions.

3. Release of Dioxins from PCP-Treated Utility Poles: This field study investigated the potential for dioxins to be released into the environment from pentachlorophenol-treated utility poles.

4. Nocturnal-Diurnal Releases from Soil: This field study investigated the possibility that soils may be a reservoir source of release into the atmosphere by measuring the difference between daytime and nighttime air concentrations of dioxins.

5. Emissions from Uncontrolled Burning of Domestic Waste: Under experimental conditions, this study measured dioxin emissions from simulated backyard burning conditions.

6. Emissions from Forest Fire Simulations: Under experimental conditions, this study measured dioxin emissions from simulated forest fires.

7. Ball Clay: This minor component of poultry feed was found to be highly contaminated, to cause elevation in poultry consuming the feed. Ball clay was later found to be a contaminant in catfish feed as well.
   • Summary of the Evidence for Natural Formation of Dioxins in Ball Clay: This study reviews the evidence suggesting that dioxin-like compounds were present in the clay as a result of natural formation processes.

   • Presence of Dioxins in Ceramics Produced From Ball Clay: This study looks at the presence of dioxins in ball clay in unprocessed and processed pottery samples.

   • Congener Profile in Mississippi Ball Clay: This study looks at the full isomer distribution in samples of ball clay.

   • An Assessment of Dioxin Levels in Processed Ball Clay: This study looks at the presence of dioxin in processed ball clay.

EXPOSURES:

1. Evaluation of the Impacts of Incinerator Emissions: Two incinerator sites have been extensively studied for their near-field impacts from dioxin emissions. These are the Columbus Municipal Solid Waste Incinerator (MSWI) in Ohio and the Shinkampo Incinerator in Atsugi, Japan.
   • Studies on the Columbus Incinerator:
     • Relationships Between Dioxins in Soil, Air, Ash, and Emissions from the Columbus MSWI: This study looks at measurements of dioxin in environmental matrices near the incinerator and ties them to the characteristics of dioxin emitted from the incinerator.

     • Evaluation of EPA's ISCST3 Model on Data from the Columbus MSWI: This study uses the data described in the previous paper in a model validation exercise.

     • Screening Level Risk Assessment on the Columbus MSWI: This assessment evaluates the potential impacts to farmers producing and consuming food near the incinerator.

   • Impacts of Dioxin Emissions From the Shinkampo Incinerator: Two articles describe the impacts of dioxin emissions from this incinerator to a Naval Base located adjacent to the incinerator.

2. Site-Specific Assessments: These studies investigate potential exposures to dioxins associated with a specific source other than incinerators.
   • The Industrialized Corridor in Calcasieu Parish, Louisiana: This study looked at dioxins, fuans, and coplanar PCBs in air in a heavily industrialized urban corridor, consisting of mixed land uses including residential, agricultural, and industrial.

   • World Trade Center: This study evaluates ambient air measurements of dioxin and evaluates them with regard to exposure and potential health risk to Ground Zero workers, nearby office workers, and nearby residents.
3. Food Chain Modeling For Dioxins: Dioxins enter the terrestrial food chain primarily in an air-to-leaf/soil-to-animal route. These studies evaluate how that process can be modeled.
   • Development and Validation of an Air-to-Beef Food Chain Model for Dioxins: This article established the framework for the modeling approach used.

   • Development of an Air-to-Leaf Vapor Phase Transfer Factor for Dioxins and Furans: This article describes a refinement to this critical factor for the transfer of dioxin-like compounds from air to leaves.

   • An Evaluation of Three Empirical Air-to-Leaf Models for Dioxin-Like Compounds: This article compares the EPA model with two other simple models for air-to-plant transfers.

   • Bioaccumulation Factors for Chickens: This article uses data from contaminated chicken feed and resulting chicken fat concentrations to derive bioaccumulation factors (BAFs) and compares them to previously reported BAFs.

4. Mass Balance Study of Dioxin-Like Compounds In Lactating Cows: By measuring the dioxin in feed ingested by lactating cows and the excretion of dioxins in milk and feces, this study attempts to verify that feed is the source of dioxins to the cows.
   • Mass Balance Study: These two articles describe the study design and results from the mass balance study, conducted in 1997 and reported on in 2000.

   • Evidence of Feed Contamination From the Mass Balance Study: The feed data was examined more closely and it was found that elevations in the feed during one of the sampling periods may have been due to the handling procedures at the agricultural research facility.

5. Food Monitoring Studies: The most direct measures of human exposures to dioxin-like compounds are measurements in food products.
   • Study of Dioxin-Like Compounds in Beef: Conducted in 1994 and reported on in 1996 and 1997, these two articles describe the first of three food studies conducted jointly by EPA and USDA.

   • Study of Dioxin-Like Compounds in Pork: This second study was conducted in 1995 and reported on in 1997.

   • Study of Dioxin-Like Compounds in Poultry: This third and final food study conducted with USDA occurred in 1996 and was reported on in 1997. It was during this study that a minor component of animal feeds, ball clay, was found to be highly contaminated with dioxins.

   • In these animal food studies, adipose reservoirs were sampled. But are adipose reservoirs the best indicator of the fat concentrations in the edible portions of the animal? These two studies compare the concentrations of dioxins in adipose reservoirs and other animal reservoirs, including the edible tissues.
     • Study on Cattle Reservoirs

     • Study on Poultry Reservoirs

   • Study of Dioxin-Like Compounds in Milk: This study utilized a radiation sampling network of EPA to evaluate milk quality nationally. Samples were collected in 1996 and 1997, and the study was reported on in 1998.

   • Data Refinements to Milk Study: This follow-up study refined the milk data earlier reported on by developing lipid-based milk concentrations, and also by doing follow-up investigations of milk initially found to be very high in dioxin-like compounds.

   • Study of Dioxin-Like Compounds in Vegetable Oil: Thirty grocery store samples of vegetable oil were analyzed for dioxin-like compounds in 1996.

6. Animal Feed Studies: The mass balance studies confirmed that the primary route of dairy cattle exposures is through their feed. These articles describe efforts by EPA to measure the dioxin-like compounds in major and minor animal feed components.
   • Presence of Dioxin-Like Compounds in Minor Components of Animal Feed Products: Following the finding of contaminated ball clay in animal feeds, the focus was on minor feed components. This study reviews results from a study measuring dioxin-like compounds in 44 samples of minor feed components.

   • Investigation of Dioxin Formation in Mineral Feed Supplements: Mineral supplements were found to be contaminated by dioxins, and subsequent investigations showed that the dioxins were formed during the manufacturing process of supplements containing copper, zing, manganese, magnesium, and iron. This article reproduces this process in the lab resulting in the formation of dioxins.

   • Levels of Dioxin-Like Compounds in Dairy Feeds in the United States: This article reports on a national study to measure dioxin-like compounds in mixed dairy feeds, and major components of these mixed feeds.

7. National Dioxin Air Monitoring Network (NDAMN): This network of monitors nationwide provide data on the concentrations of dioxin-like compounds in air in background areas of the United States.
   • Results: This article present results from different calender years
     • Overview article on NDAMN from 1998 - 2002

   • Analytical Chemistry and Other Issues Associated With NDAMN Sampling: Measuring the particle and vapor phase factions from this study can prove uniquely challenging and sometimes results are unexpected.
     • This article describes general analytical issues

     • This article describes NDAMN quality assurance procedures

     • This article describes method blank concentrations of dioxins

     • This article identifies anomalous results from NDAMN

8. Urban Air Transect Study: This study measured dioxin-like compounds upwind and downwind of a major urban city in the United States to investigate the hypothesis that urban areas represent sources of dioxin-like compounds.

9. Analytical Chemistry: These articles describe the procedures and complexities associated with measuring dioxin-like compounds in food and other matrices.
   • Achieving Part Per Trillion Levels in Food Matrices: This article describes the procedures used to measure the dioxin-like compounds in animal fat matrices, using the beef survey samples as the prototype.

   • Background Contamination by Coplanar PCBs: Presence of background coplanar PCBs in laboratories can compromise analytical results. Special procedures used by EPA mitigate this source of contamination.

   • Method Evaluation to Measure Persistent Bioaccumulative Toxic Pollutants in Cow Milk: This paper discusses not only the dioxins, furans, and PCBs, but also pesticides, polycyclic aromatic hydrocarbons (PAHs), polychlorinated naphthalenes (PCNs), brominated diphenyl ethers (BDEs), and the metals lead and cadmium.

   • Quality Assurance Project Plans for Dioxin Exposure Initiative Studies: This article describes the development of quality assurance project plans, QAPPs, that accompany all laboratory data developed as part of this research program.

10. Policy Issues in Evaluating Dioxin Exposures: Procedures for conducting cancer and non-cancer risk assessments for dioxin-like compounds are not always straightforward. These two articles discuss some of the issues associated with dioxin risk assessment.
    • Utilizing a "Margin of Incremental Exposure" Procedure for Non-Cancer Risk Assessing: This article describes a procedure to evaluate the amount of exposure above background that can be attributed to a specific source of dioxin exposure.

    • Evaluating Terrestrial Food Chain Impacts Near Sources of Dioxin Release This article reviews similarities and differences in Agency risk assessments evaluating the "subsistence farmer" located near sources of dioxin release.

11. An Evaluation of Infant Exposures to Dioxin-Like Compounds: This study uses a simple pharmacokinetic model to describe the impact of breast-feeding on the body burden of dioxin-like compounds in infants.

12. Pilot Survey of Levels of Polychlorinated Dibenzo-p-dioxins, Polychlorinated Dibenzofurans, Polychlorinated Biphenyls and Mercury in Rural Soils of the United States (Final): This study is a compilation of the measurements of levels of dioxins, PCBs and mercury in soil samples from numerous rural locations across the country.

TRENDS:

1. Sediment Core Study: This study measures dioxin-like compounds in several layers of cores taken from 11 lakes in the United States. By carbon-dating the core layers, observations about the prevalence of dioxin deposition over centuries can be made.

2. Survey of Dioxins in Historical Meat Samples: This study measures dioxin-like compounds in 14 preserved samples of meat taken from different decades of the 20th century.

3. Pharmacokinetic Modeling of Body Burdens in the 20th Century: These studies use simple pharmacokinetic models, along with available data on body burdens in the 1970s, 1980s, and 1990s, to describe the trends in body burden during the 20th century.
   • This study is specific to 2,3,7,8-TCDD:

   • This study is on dioxin TEQs.

• Exposure and Human Health Reassessment of 2,3,7,8-Tetrachlorodibenzo-P-Dioxin (Tcdd) and Related Compounds National Academy Sciences (External Review Draft) (2004)