Dioxin: Environmental Impacts and Potential Human Health Effects

This issue brief presents a short background on the physical/chemical properties of dioxin, describes several existing sources of possible human exposure, and highlights what is currently known about its environmental impacts and human health effects. Congressional interest is intense at this time because of large numbers of Vietnam veterans' claims for benefits associated with use of herbicides in that war as well as because of certain incidents of potential significance to health involving disposal of wastes containing dioxin.

CICXIN: E N V I R 3 N M E N T A L I M P A C T S AND P O T E N T I A L H U M A N H E A L T H E F F E C T S ISSUE BRIEF NUMBER IB83079 AUTHOR: M i c h a e l M. Simpson Science Policy Research Division T H E L I B R A R Y OF C O N G R E S S CONGRESSIONAL RESEARCH SERVICE MAJOR I S S U E S S Y S T E M D A T E O R I G I N A T E D 04/18/83 DATE UPDATED 10/21/83 FOR A D D I T I O N A L I N F O R M A T I O N C A L L 2 8 7 - 5 7 0 0 CRS- 1 ISSUE DEFINITION Animal studies indicate that dioxin is a highly toxic .compound; however, there have been no human deaths attributed to exposure to dioxin. Current concerns about dioxin center around the potential adverse environmental impacts a s well a s the possible harmful human health effects of trace dosages encountered a s environmental contaminants. The environmental impact a n 8 human health effects of such exposure to djoxin are not clear a t this time. Conflicting statements regarding the effects of dioxin exposure are found in both scientific and popular journals. This controversy stems from the lack of conclusive findings from well-defined exposure studies. Policymakers are consequently confronte5 with deciding whether or not to take regulatory cr other action t o address fears about the threat to health and the environment, in the absence of confirmed findings on the risks associated with dioxin. This issue brief presents a short background on the physical/chemical properties of dioxin, describes several existing sources of possible human exposure, and highlights.what is currently known about its environmental impacts and human health effects. Congressional interest is intense a t this time because of large numbers of Vietnam veterans' claims for benefits associated with use of herbicides in that war a s well a s because of certain incidents of potential significance to health involving disposal of wastes Veterans' Complaints conraining dioxin. (See also IB83043 -- Agent Orange: and Studies of Health Effects.) BACKGROUND AND POLICY ANALYSIS The compound dioxin was identified when i t was synthesized by a research technician in the mid-1950s. The technician was exposed to the dioxin and subsequently developed a severe case of chloracne which required hospitalization. This event provided the first clue a s to the potential human health effects of dioxin exposure. There a r e many different forms of dioxin; the form most commonly r e f e r r e d (TCDD). Dioxin is a to a s dicxin is 2 , 3 , 7 , 8 , - t e t r a c h l o r o d i b e n z o - p - d i o x i n (2,4,5,-trichlorophenol). contaminant that occurs in the production of TCP When TCP is used to make other compounds, a dioxin contaminant may be passed along to the new substance. The compound TCP i s used in the proauction of several compounds, including the herbicide 2,4,5,-T (2,4,5,-trichiorophenoxyacetic acid) and the compound hexachlorophene (bis-trichoro-2-hydroxyphenol methane), whi.ch i s used in soaps and disinfectants. The level of dioxin contamination in 2,4,5-T until 1970 averaged 1-5 parts per million (pprn) with a few samples a s high as 4-7 ppm. After-1970, levels of dioxin contamination were required to be reduced to less than 0.1 ppm in 2,4,5-T. The U.S. Pharmacopeia has established a maximum detectable limit of 0.05 ppm dioxin for hexachlorophene; the actual content measured in (A physical/chemical hexachlorophene has been less than 0.005 ppm. description of the compound dioxin is provided in the appendix.) Policymakers have often been called upon to make risk-regulating decisions CRS- 2 in the absence of sufficient scientific data. Frequently such data a s may be available are conflicting. In making such policy decisions, Congress considers a number of factors in determining allowable risk to public health and the environment, a s well a s the economic impact and net social benefits involved. Policy decisions about the regulation of dioxin may affect the general population, several industries, and foreign trade; At present, there are several organizations, activities, agencies, and interest groups concerned about the issue of dioxin. Their positions are reflected by their individual policy statements. o The Veterans Administration (VA) has a long-standing and continuing concern over the effects of dioxin exposure, stemming from the use of Agent Orange in Vietnam. The VA's review of available literature and ongoing studies indicates that, as yet, no consensus exists within the scientific community concerning the causal relationship between dioxin exposure and those health problems experienced by some Vietnam veterans. o The Dow Chemical company acknowledges that dioxin i s highly toxic and produces ill health effects in laboratory animals; however, a t concentrations found in the environment, the company believes dioxin does not pose a health hazard to humans. o The American Medical Association (AMA) has not confirmed any chronic aCverse human health effects related to environmental exposure to dioxin other than chloracne, but has encouraged further research in this area. o As a result of studies conducted a t sites contaminated with dioxin, the Centers for Disease Control (CDC) has established a safe exposure limit for dlsxin in the environment at 1.0 part per billion (ppb). The CDC's position is that below 1.0 ppb the individual i s not a t risk; above 1.0 ppb, inadequate data exist to determine if any risk is present. The exposure limit is both site and condition specific -- i.e., this limit may vary from location to location, depending upon the level of dioxin contamination, and the condition of exposure. CDC is presently conducting research on Vietnam veterans exposed to dioxin (phenoxy herbicides) to better define the health risks from exposure. o The National Institute for Occupational Safety and Health (NIOSH) claims that evidence i s increasing to support a link between occupational exposure to dioxin and soft,tissue sarcoma. o The Veterans of Foreign Wars (VFW), in its concern for the health of veterans in general, finds that although no confirmed relationship has been established between dioxin exposure and specific adverse health effects, there are sufficient trends reportea in the scientific journals to suggest some health risk. The VFW is seeking compensation for any veteran suffering from specific conditions reported to result from dioxin exposure. o Also supporting the idea of compensation is the Vietnam Veter2ns of America (VVA). The VVA maintains that scientific evidence supports the association of adverse human health effects and dioxin exposure. o The Sierra Club and the Environmental D-efense Fund (EDF) have taken stronger positions against dioxin. The Club and EDF believe dioxin presents a health hazard and recommend further research to determine the degree of hazard to man. They call for the removal of all uses of chemicals contaminated with dioxin and stricter control over production of chemicals that could have dioxin a s a contaminant. CRS- 3 IB83079 The diversity of these pclicy positions reflects the scientific data. lack UPDATE-10/21/83 of conclusive Dioxin Research Dioxin research is presently being conducted in several private and Federal research facilities. Federal agencies have budgeted over $101000,000 for dioxin research during fiscal year 1983 (FY83) and more than $50 million is scheduled to be spent on dioxin research in FY84. The major purp0s.e of this research i s to determinate the human health effects and environmental impacts associated with dioxin exposure. In addition to Federal expenditures, the Dow Chemical Company has made $3,000,000.00 available to researchers to identify the human health effects resulting from Cioxin exposure. Concern has been expressed concerning the coordination and control of research efforts by individuals, interest groups, researchers, and Federal agencies. Superf crnd At present, funds used to temporarily or permanently relocate residents living in dioxin-contaminated areas come from the Superfund budget. If the trend of buying these contaminated areas continues, additional funding of the Superfund program will become necessary. (See IB83D64 -Superfund: Hazardous Waste Clean-up -- for details of the complete issues associated with the Superfund.) Sources of Exposure to Dioxin Public concern about exposure to dioxin has been heightened a s a result of increased awareness of several sources of proven or possible exposure: 1) the use of the herbicide "Agent Orange" in aerial spraying operations during the Vietnam conflict (there were also occasional uses of herbicides such a s 2,4,5-T for brush control in civilian applications until 1979. Since 1979, uses of 2,4,5-T have been limited to rice crops and rangelands; 2) the from municipal Seveso, Italy, chemical plant accident; 3) emissions incinerators and some fossil fuel power plants; 4) the; spreading of dioxin contaminated oil for dust control in Missouri. and 5) unknown sources of dioxin in Michigan, New Jersey, Massachusetts, and Oregon. 1. Herbicide Aerial Spraying. From 1 9 6 2 to 1971, herbicide aerial spraying operations were conducted by the U.S. in the Republic of Vietnam. The peak periods of spraying were 1968 and 1969. According to the U.S. Air Force, the herbicide most eften sprayed was "Agent Orange," a half-and-half mixture of the herbicide 2, 4,-D ( 2 , 4 - d i c h l o r o p h e n o x y a c e t i c acid) and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid). Dioxin is a contaminapt of 2,4,5-T. Average dioxin levels in "agent orangew were estimated a t 2 ppm with a high of 4 7 ppm and a low of 0.02 ppm. The Environmental Protection Agency (EPA) has since recommended the limit for the contaminant dioxin in 2,4,5-T a t 0.1 ppm (May 1971). Both U.S. air and ground forces were subjected to possible dioxin exposure while in specific . CRS- 4 regions of the Republic of Vietnam (see IB83043 Complaints and Studies of Health Effects). IB83079 -- Agent UPDATE-10/21/83 Orange: Veterans' 2. Seveso, Italy, Chemical Plant Accident. The Seveso, Italy, accident (July 1 0 , 1976) involved an explosion a t a chemical plant where TCP was manufactured. A cloud of TCP with the contaminant dioxin escaped from the chemical plant a s a result of the explosion. The cloud, estimated to contain roughly 3 grams of dioxin, was dispersed by the wind across a residential area adjacent to the plant. Several hundred people were exposed to the, chemical cloud. Within the first year after the accident 187 cases of chloracne were reported; 1 6 4 were children and 23 were adults. Eight of the children with chloracne also had severe chemical burns; eleven other children had chloracne and mild chemical burns. Several other children that did not develop chloracne did develop erythema (red skin patches). Very few adults developed chloracne or chemical burns. Studies are still being conducted on the exposed population to determine the chronic health effects. 3. Power Plant and Incinerator Emissions. Dioxin has also been identified a s an emission from some fossil fuel power plants and municipal incinerators. The dioxin is produced during the incomplete combustion of fuel or waste that contains such compounds a s chlorophenols, chlorinated benzenes, and biphenyl ethers. The amount of discharge (smoke stack emissions) is dependent upon incinerator operation, fuel, and combustion temperature. 4. State of Missouri Contamination. Dioxin contamination of soil in Kissouri dates back t o 1971, when dioxin-contaminated waste oil was applied to the soil for dust control. At a horse arena where the dioxin-contaminated waste oil was applied several horses died. Several other sites in the State also were sprayed with the dioxin-contaminated waste oil for dust control. Not all sites have been positively identified or tested. Dioxin contamination sites in the State have been identified to have levels between 1.0 ppb-1,800 ppb. Some estimates for suspected dioxin contamination sites are a s high as 1.0 ppm. The problem of dioxin site identification and cleanup has been complicated by rainfall, surface run-off, and flooding which spreads the dioxin contaminatedsoil. At present, efforts are underway to identify all dioxin sites in the State and either clean up the site or possibly relocate the residents. As a result of the scil being contaminated with dioxin, the EPA has requested the Federal Emergency Management Agency (FEMA) to permanently relocate the residents of Times Beach and 1 1 families of Imperial, MO. The EPA has also requested FEMA to temporarily relocate three St. James, MO Families. 5. Michigan and New Jersey Contamination. Certain sites in Michigan and New Jersey have recently been identified a s having been contaminated with dioxin. Dioxin has been detected in rivers around the Dow Chemical Plant in Midland, Michigan, and a t three sites near the Diamond Alkali Corp. plant in New Jersey. Both plants a r e reported to have produced Agent Orange contaminated with dioxin during the Vietnam War. In New Jersey At presen-t only one site has been identified in Michigan. there are 5 0 additional sites that are scheduled for eioxin contamination CRS- 5 testing. The specific source or sources of dioxin contamination remain to be determined in both States. Further investigations will be conducted in each State to identify any additional dioxin contaminated sites. 6. Identification of Sites Possibly Contaminated with Dioxin. In 1980, the Environmental Protection Agency compiled a list of sites 33 States possibly contaminated with dioxin. These sites -will be tested determine if they are actually contaminated. in to Massachusetts is one of the suspect States. Several ponds and lakes in the State will be tested during the summer of 1983. The ponds and lakes may have been contaminated when herbicides were sprayed on them to control water weeas in the 1950s and 1960s. It has been reported that dioxin-contaminated sites also exist in Oregon, with dioxin concentrations up to six times greater than those at Times Beach, Mo. The source of the dioxin in Oregon is unknown at this time. Environmental Effects 1. Biological Accumulation and Elimination. Stadies have demonstrated that accumulation and elimination of dioxin occurs in many animal species. It has been reported that dioxin, at concentrations found in the environment, does not accumulate in animal tissue to any significant degree. It would appear that the rates of accumulation and elimination dependent upon the environmental concentration, conditions of exposure, animal species. are and Few studies have been conducted to determine whether dioxins are accumulated in plants. Those studies that have addressed this question appear to indicate that very little dioxin accumulation occurs in plants. When accumulation did occur the lowest levels were recorded in the fruits and leaves with the highest levels found on the surface of roots. It is interesting to note that when plants were transplanted from dioxin-contaminated soil to uncontaminated soil, the dioxin levelsaccumulated in the plant disappeared. 2. Soil Contamination. Some studies have'been conducted to determine if dioxin is persistent in most types of soils. Those studies that evaluate dioxin persistence in soil found that over 90% of the dioxin could be detected in the soil one year after the original contamination occurred. This would indicate that a strong bond is established between dioxin and most soils. The persistence of dioxin in the environment has been attributed to these strong bonds. 3. Water Contamination. Dioxin is not very soluble in water (highly insoluble). The greatest danger of contamination of the rivers and streams is from dioxin-contaminated soil run-off. The eroded dioxin-contaminated soil particles could Settle on the bottom of the stream or could be carried with the flow of' the stream. CRS- 6 Disposal Methods Small quantities of dioxin can be disposed of by physiochemical, chemical, and microbiological means. Physiochemical means include: ultraviolet light; gamma rays; or hydrogen donation. An ultraviolet l i g h t treatment was developed recently for commercial disposal of dioxin-contaminated liquid Chemical disposal i s possible wastes. T h e treatment i s 98% efficient. utilizing alkaline dehydrochlorination, reduction with iron chlorides, oxidation with ruthenium tetroxide, chloridides, and chlorolysis. Alkaline dehydrochlorination uses anhydrous a l k a l i metal salts of polyhydroxy alcohols to remove the chlorine from the chlorinated dioxins. This is accomplished by mixing dioxins, a l c o h o l , a n d a water solution of any (alkaline) metal hydroxide. Reduction of dioxin with iron chlorides i s being studied; this method had limited success. has Oxidation with ruthenium tetroxide i s a n acceptable method f o r destroying i s usually used t o destroy dioxin small a m o u n t s o f . d i o x i n . This method produced i n the laboratory. Chloriodide research i s being conducted i n the hopes of using chloriodides to destroy dicxin i n contaminated soil. Micellar catalysts a r e used un the process. being investigated. Final research Chlorolysis I S a process currently results r e m a i n to S e determined. M i c r o b i o l o g i c a l ~ m e a n s depend on microbes to destroy t h e dioxin. T h i s method has been field tested with limited success; d u e to i t s high cost i t may n o t be considered practical f o r bulk disposal. Research i s underway to develop a better microbial degradation method. Such degradation has not proven successful t o date. Larger quantities of dioxin can be disposed of using more traditional means such as: a) incineration; b) perpetual repository storage (not true disposal); c) secure landfill (presently permitted but may still present a n environmental hazard later); with dioxin this i s n o t actually and C ) entombment (concrete mixed disposal) . -- Dioxin i s easily destroyed by natural sunlight i n a very short time. The difficulty in this form of disposal resnlts from the f a c t that natural light destruction of d i o x i n ' i s only surface active (i.., i t destroys only the layer on the surface directly exposed to the natural sunlight.) General Exposure Standards Two a g e n c i e s have established exposure standards f o r dioxin and a tBird exposure limit. T h e Environmental Protection has recommended a maximum Agency's Scientific Advisory Panel i n 1 9 8 0 established the " n o ' observable effect level" (NOEL) f o r dioxin a t 0.001 micrograms dioxin p e r - kilogram of body weight. per day (mg/kg/day). T h e NOEL i s defined a s a dose b e l o w which no c a r c i n o g e n i c , teratogenic, o r reproductive effect i s observed. T h e F e d e r a l Food and Drug Administration (FDA) set the dioxin levels i n edible f i s h a s not to exceed a l i m i t of 5 0 . p p t (parts per trillion). I t has (CDC) that individuals beer, recommended by t h e Centers for Disease Control not be exposed t o l e v e l s of dioxin greater than 1 ppb i n soil f o r a n y CRS- 7 IB83079 UPDATE-10/21/83 extended periods of time. The chemical industrial exposure limit for dioxin weight was set by the EPA to protect workers in the related fields. Biological Effects -- of 0.0007 mg/kg body chemical industry and Animals Experiments on laboratory animals show interspecies differences (i.e., no two species react in the same way) in response to a high concentration acute exposure to dioxin. This response would i'ndicate that dioxin has a different acute toxic effect in each animal species. However, when exposure levels a r e high enough to cause death, the length of time between exposure and death (the latent period) i s similar for each species. How the dioxin causes death in experimental animals is not known. When laboratory animals are exposed t o lower concentrations of dioxin, where death i s not expected to occur, two sets of symptoms are generally observed. The first set of symptoms, common to all species, includes: a) chloracne; and b) the development of horny skin layer (hyperkeratosis). The second set of symptoms which i s specific to each individual species includes: a) in pregnant female mice, dioxin exposure results in the production of some abnormal offspring (teratogenic effect); b) in pregnant female mice and some other species, dioxin exposure causes the death of some of the unborn offspring (fetotoxic effect); c) in chickens a unique lesion is developed (hydropericordium); d) in some animal species a n infiltration of tissues with fluid occurs (edema); e) in rabbits liver disturbances are common; f) in monkeys conversion of the meibomian gland occurs (the gland in the eyelid changes from a sebaceous fluid producer to a keratin producer); and g) in guinea pigs suppression of the immune system occurs. Although reproductive disorders were observed in female mice, n o reproductive disorders were observed in male mice exposed to dioxin a t identical concentrations. Biological Effects -- Man No human deaths have been reported after an acute exposure to dioxin. The most prominent effect observed in man from a n acute or chronic exposure t o dioxin is chloracne. Chloracne can range in severity and extent. The more severe cases may involve extensive acne-li-ke eruptions of blackheads,. abcesses, and cysts initially on the face, giving the appearance of grayish sheets. The most severe cases may involve the total body. Chloracne is not a condition that is unique to dioxin exposure; it may a.lso occur from expcsure to many other chlorinated compou'nds. The chronic effects of exposure to dioxin (other than chloracne) a r e not well understood. Although several symptoms, diseases, and conditions have been described by individuals chronically exposed to dioxin, there is not sufficient information t o establish a cause-and-effect association. The diseases or conditions .that 2) liver function have been reported include: 1) enlarged liver; (a disturbance abnormality; 3 ) neuromuscular effects; 4) deranged porphyrin in production of porphyrin -- a natural pigment produced by tae body); 5) spontaneous abortion; 6 ) congential malformation; 7) cancer; and 8) chromosomal aberrations. 1. Liver Enlargement. Enlargement of the liver has been reported in some exposed individuals. However, mortality among the dioxin-exposed individuals who displayed an CRS- 8 enlarged liver w a s not statistically different from that of non-exposed individuals (individuals with normal livers). Any relationship between dioxin exposure a n d the liver enlargements i s unclear a t this time. 2. Liver Function Abnormality. Liver dysfunction has been observed i n s o m e individuals who a l s o were accidently exposed to dioxin. Individuals exposed to l o w l e v e l s o f dioxin may have an abnormal liver f u n c t i o n , yet n o temporary o r permanent d a m a g e may occur. Exposures to very high levels o f dioxin may cause a n a b n o r m a l liver function with s o m e signs of permanent damage. Any relationship between dioxin exposure a n d liver function abnormality i s unclear a t this time. 3. Neuromuscular Effects. Some individuals exposed t o dioxin r e p o r t a weakness i n their l o w e r limbs. T h i s effect has n o t been observed i n a n y animal trials. The impairment reported seems to be slight, affecting muscular coordination without a n y other apparent s i d e effects. Any relationship between dioxin exposure and the neuromuscular effect i s unclear a t this time. 4. Deranged Porphyrin. Porphyrin derangement, which may result i n spotting of the s k i n , i s known to have a genetic a s well a s a n environmental cause (e.g., environmental exposure to hexachlorobenzene, polychlorinated biphenyls and dioxin). Any relationship between d i o x i n - e x p o s u r e and t h e porphyrin effect i s unclear a t this time. 5. Spontaneous Abortions. Spontaneous abortions have been reported a s a possible a d v e r s e health effect of dioxin exposure. A review of r e c e n t studies indicates that there appears to be n o difference between the r a t e of spontaneous abortions within the Cioxin-exposed populations a n d the non-exposed populations. 6. Congenital Malformations. It has been reported that a s a result of dioxin exposure congenital malformations h a v e occurred. There appears to be no difference i n t h e number of congenital malformations occurring i n dioxin exposed and non-exposed populations. T h i s was confirmed in a comparison made between the r a t e of congenital ma,lformations observed after the S e v e s o , I t a l y , accident and t h e estimated world rate. 7. Cancer. Cancer has been suggested a s a n e f f e c t of dioxin exposure. It. i s difficult to demonstrate a cause-and-effect relationship between dioxin exposure and cancer. There a p p e a r s to be n o difference i n the o v e r a l l cancer eeatt! rate between the dioxin-exposed a n d the n o n - e x p o s e d - populations. According to s o m e studies, there does a p p e a r t o be s o m e increase i n the incieence of soft tissue sarcoma in dioxin-exposed populations. NIOSH claims evidence i s increasing to support a link between occupational exposures t o dioxin and soft tissue sarcoma. Other s t u d i e s , conducted both i n this country and o v e r s e a s , have shown no increase in soft tissue sarcomas r a t e s a s a result of dioxin exposure. - CRS- 9 IB83079 UPDATE-10/21/83 It has recently been reported that an association may exist between stomach cancer and dioxin exposure. Evidence in support of either association i s not sufficient to make a positive confirmation of cause and effect. 8. Chromosomal Aberrations. Cytogenetic stuCies (those relating to the function and structure of t h e cell) to date do not indicate an increase in the frequency of chromosomal aberrations a s . a result of dioxin exposure. When the prevalence of chromosomal aberrations is compared between the dioxin-exposed individuals and the total population a t large no signi'ficant difference is observed. Summarv Studies indicate that dioxin is a highly toxic chemical that may persist for many years in the environment. Plants do not appear to accumulate great amounts of dioxin. . A n i m a l s appear to accumulate and eliminate dioxin a t different rates depending on environmental conditions and animal speciesBodies of water generally become contaminated from dioxin-contaminated soil run-off a s a result of erosion. Soil forms a strong bond with dioxin which is mainly responsible for the persistence of the dioxin in the environment. Dioxin may be disposed of by traditional methods such a s incineration, perpetual storage, landfill, and entombment. Dioxin molecules a r e destroyed by sunlight on exposed surfaces. Animal exposure studies demonstrate species differences for the effects of dioxin. Chronic exposures appear to result in specific health effects for each animal species. Chloracne i s the most consistent condition of dioxin exposure in humans. Other symptoms have been reported, yet no cause-and-effect association has been confirmed. Points for Further Consideration Future issues w.hich may confront policymakers include: (a) identification of cause-effect relationships with rega,rd to the human health effects of dioxin exosure; (b) proposed establishment of dioxin industrial discharge requirements; (c) establishment of final dioxin disposal requirements (changing the chemical character of dioxin); (d) initiation of further chronic exposure studies with a ~ i m a l s ; (e) development of new waste discharge methodologies; (f) requirement for extensive acute and chronic testing of new chemicals prior to marketing; ( g ) identification of one Federal agency t o coordinate all dioxin and Agent Orange research efforts; (h) examination of the need for some form of a victim compensation program, based upon a chosen level of acceptable risk, to protect the individual from environmental sources of dioxin (a hazard insurance program); and (i) examination of the need for the development of a risk analysis program for all hazardous waste sites. HEARINGS U.S. Congress. House. Committee on Energy and Commerce. Subcommittee on Oversight and Investigations. Defining health emergencies under the superfunded statute: - r e c e n t PCB and dioxin cases. Hearing, 97th Congress, 2d session. Nov. 1 9 , 1982. Washington, U.S. Govt. Print. Off., 1983. 370 p. U.S. Congress. House. Committee on Interstate and Foreign Commerce. Subcommittee on Oversight and Investigations. Agent orange: exposure of Vietnam veterans. Hearing, 96th Congress, 2d session. Sept. 25, 1986. Washington, U.S. Govt. Print. Off., 1981. 249 p. ----- Involuntary exposure to agent orange and other toxic spraying. Hearings, 96th Congress, 1st session. June 26-27, 1979. Washington, U.S. Govt. Print. Off., 1980. 256 p. U S . Congress. House. Committee on Veterans Affairs. Subcommittee on Oversight and Investigations. Current status of agent orange studies. May 6 , 1981. Washington, U.S. Govt. Print. Off., 1981. 385 p. U.S. Con'gress. House. Committee on Veterans Affairs. Subcommittee on Medical Facilities and Benefits. Scientific community report on agent orange. Hearings, 96th Congress, 2d session. Sept. 1 6 , 1980. Washington, U.S. Govt. Print. Off., 1981. 145 p. ----- Oversight hearing to receive testimony on agent orange. Hearing, 96th Congress, 2d session. Feb. 25, 1980. Washington, U.S. Govt. Print. Off., 1980. 121 p. ----- Oversight hearing to receive testimony on agent orange. Hearing, 96th Congress, 2d session. July 22, 1980. Washington, U.S. Govt. Print. Off., 1981. p. 4 5 9 p. U.S. Congress. House. Committee on Veterans Affairs. Ad Hoc Subcommittee. Status of Vietnam veterans in the Bay area. Hearing, 96th Congress, 2d session. Apr. 1 0 , 1980. Washington, U.S. Govt. Print., Off., 1980. 64 p. CHRONOLOGY OF EVENTS 10/20/83 -- U.S. EPA confirmed the presence of dioxins and furans in municipal incinerator emissions. 07/00/83 -- Contaminated sites reported in Massachusetts and Oregon. 06/00/83 -- Soil contamination with dioxins found in Michigan and New Jersey. Missouri clean up of dioxin spills begins. 11/19/82 --- 12/03/80 -- P.L. 96-510, Comprehensive Environmental Re-sponse Compensation and Liability Act 1980 (CERCLA), clean up of hazardous waste sites. "Superfundw 02/00/83 Hearings held by Subcommittee on Oversight and Investigations of the Committee on Energy and Commerce. Hearing on the hazards of dioxin. -- 10/21/76 -- 10/11/76 -- P.L. 94-469, Toxic Substance Control Act, the control of all toxic substances not covered by other toxic substances control. 07/10/76 -- Seveso, Italy chemical plant explosion, dioxin contaminant spread over local region. 07/19/75 -- P.L. 94-56, Hazardous Material Transportation Act. (Amended 1976 to cover the transport of toxic materials. ) '2/16/74 -- P.L. 93-523, Safe Drinking Water Act. (Amended 1977 to eliminate contaminants from discharge or entry into water sources.) 10/18/72 -- P.L. 92-500, Clean Water Act. (Federal Water Pollution Control Act.) (Amended 1977 to cover discharge of toxic pollutants into water.) OC/CO/71 -- 12/31/70 -- 1960-70 -- P.L. 94-580, Resource Conservation and Recovery Act (RCRA), control of hazardous wastes. Missouri sites were contaminated with Cioxin. P.L. 91-604, Clean Air Act. (Amended 1 9 7 7 to cover discharge of hazardous pollutants into the air. ) Agent orange contaminated with dioxin used in Republic of Vietnam for aerial spraying operations. 00/00/56 -- Dioxin identified. Unknown -- Incinerator production of dioxin. ADDITIONAL REFERENCE SOURCES over nor and Axelrod D. Dioxin exposure report to the legislative April 1982. New York State Department of Health. 1982. Barnes, D.G. 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OEHL TR-78-92 APPENDIX 1 Structure and physical/chemicai characteristics of 2,3,7,8-tetrachlorodibenzo-P-dioxin, 'E'DD or dioxin. ' Structure Physical Characteristics molecular weight melting point, decomposition point, Chemical Characteristics Solubility, grams/liter ortho-dichlorobenzene chlorobenzene Orange Herbicide benzene chloroform acetone normal-oc t ano 1 lard oil ' me than01 water REFERENCE: Young, A.L., Calcagni, J.A., Thalken, C.t., and Tremblay, J.W. The toxicology enviroumental fate and human rirk of herbicide orange and it8 aroociated dioxin. U.S. Air Force Report, OKHL I%-78-92, October 1982. page 1-22