Detailed study on the levels of polychlorinated dibenzo-p-dioxins,polychlorinated dibenzofurans and polychlorinated biphenyls in Yusho rice oil

One bottle of Yusho rice oil was obtained from a Yusho family in 1998. The levels of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) in the causal oil were investigated with two different approaches and the individual concentrations of all the 17 2,3,7,8-substituted PCDD/F and 14 coplanar PCB (Co-PCB) congeners were elucidated for the first time. The concentrations of PCDDs and PCDFs were found to be 0.60 and 8.8 ppm, respectively. For PCBs, more than 130 PCB peaks were observed and a total concentration of 850 ppm including 170 ppm of Co-PCBs was obtained. The toxic equivalents (TEQs) of PCDDs, PCDFs, and Co-PCBs were calculated to be 17, 470, and 120 ppb, respectively. The relative contribution of these classes to the total TEQ in Yusho oil is 3%, 77%, and 20%, respectively, indicating that PCDFs play a major role in the toxicity of Yusho oil. Furthermore, it was confirmed that 2,3,4,7,8-penta-CDF contributes 58% to the total TEQ, supporting the view that this compound is the principal causal agent in Yusho poisoning. It is noteworthy that the most toxic 2,3,7,8-tetra-CDD was newly discovered, although it contributes only 0.1% to the total TEQ. Based on our data, the smallest TEQ intake during the latent period was estimated to be 0.067 mg for Yusho patients. This value is about 60% of that previously reported, suggesting a lower minimum threshold level for the development of the toxic symptoms of Yusho.     

Recent survey and effects of cooking processes on levels of PCDDs,PCDFs and Co-PCBs in leafy vegetables in Japan

We report here the latest levels of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) and coplanar polychlorinated biphenyls (Co-PCBs) in leafy vegetables in Japan as well as the effect of cooking processes on the reduction of these contaminants. Three kinds of leafy vegetables (“komatsuna”, lettuce and spinach) from seven districts in Japan in 1998 were analyzed for the 2,3,7,8-chlorine substituted PCDD/Fs and three non-ortho-PCBs (#77, 126 and 169). The mean total TEQ levels (using the WHO-TEFs) in the komatsuna, lettuce and spinach were 0.094, 0.025 and 0.196 pg/g fresh weight, respectively. The TEQ levels are dominated by 2,3,7,8-TCDD, 1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF and 3,3^′,4,4^′,5-PeCB in many of the samples. For one of these isomers, the 2,3,4,7,8-PeCDF TEQ levels showed good correlation with the total TEQ levels in the samples (r=0.957). This suggests that 2,3,4,7,8-PeCDF may be an indicator for dioxin contamination in the analysis of the leafy vegetables. Also, the effects of two cooking processes (washing and washing followed by boiling) on the dioxin levels in two types of spinach samples were investigated. On average, in both samples, the total concentrations of the PCDDs, PCDFs and Co-PCB were reduced to about 38%, 73% and 88% of the initial concentrations by washing, and to 21%, 35% and 61% of the initial concentrations by washing followed by boiling. The total TEQ levels were reduced to about 30% of the initial TEQ levels by washing followed by boiling. Significant reductions in the TEQ levels were observed in the cooked samples. Thus, the cooking processes may reduce the risk of dioxin intake from the leafy vegetables.     

Nationwide study of dioxins in the freshwater fish Carassius auratus (gibelio) langsdorfii (crucian carp) in Japan: concentrations and estimation of source contribution ratios

We investigated dioxin concentrations in freshwater fish in Japan by standardizing species to detect subtle decreasing trends of dioxin concentrations in the future with the reinforcement of regulations. The fish studied were crucian carp (Carassius auratus (gibelio) langsdorfii), an omnivorous species. Fish and sediments were collected from 14 rivers and lakes located in remote areas, agricultural areas, and small and large cities throughout Japan. The total toxic equivalent (TEQ) dioxin concentrations at the three remote sites were about 20% of the concentrations at the other 11 sites, which all had similar concentrations. The average concentrations in fish collected from these 11 sites were 0.69pgTEQg(-1) wet wt. (95% CI 0.52-0.85) or 57.3pgTEQg(-1) fat (95% CI 47.9-66.7). There were notable differences in congener profiles of polychlorinated p-dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) between sampling areas. A chemical mass balance method was used to estimate the proportions of dioxin contributions from different sources. The sampling areas were classified into four groups on the basis of the predominant source of dioxin contamination: a combustion group, a chlornitrofen herbicide group, a chlornitrofen and pentachlorphenol herbicide group, and a remote group. The congener profiles of dioxin like polychlorinated biphenyls (DL-PCBs) were almost the same in all areas and close to those in Kanechlor, which indicates that pollution from PCB products has spread throughout Japan. From samples collected during the spawning season, it was determined that about 20% of the dioxins in adult females were transferred to the eggs, resulting in higher dioxin concentrations in adult males than in females. Biota-sediment accumulation factors (BSAFs) of 2,3,7,8-substituted PCDDs/DFs for crucian carp were larger than those of non-2,3,7,8-substituted congeners, and BASFs decreased with increasing number of chlorines. The BSAFs of DL-PCBs were 10 times greater than those of PCDDs/DFs, and BSAFs of mono-ortho type DL-PCBs were higher than those of non-ortho types.     

Distribution of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and non-ortho coplanar polychlorinated biphenyls in river and offshore sediments

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and non-ortho chlorine substituted coplanar polychlorinated biphenyl (Co-PCBs, non-ortho Cl CBs) in river and offshore sediment samples were analyzed isomer-specifically using (13)C-labeled their respective internal standards and a selected ion monitoring method of high resolution gas chromatograph-mass spectrometry (GC-MS). These compounds were found in all samples analyzed. The average concentrations of the total PCDDs, PCDFs and Co-PCBs in the 23 sediment samples taken from rivers were 11 000, 1300 and 160 pgg(-1) of dry wt, respectively, those in six offshore sediments were 7600, 980 and 52 pgg(-1), respectively. The concentrations of Co-PCBs were much lower than those of PCDDs and PCDFs in all sediment samples. The magnitude of these concentrations was in the order of lower reach of river > offshore area > upper reach of river. The concentrations of PCDDs and PCDFs in the rural river were higher than those in the urban river, whereas the Co-PCB concentration in an urban river was six times higher than that in a rural river. The Co-PCB concentrations in the urban area and industrial area were higher than that in any other area. These findings suggest that the pollution by PCDDs and PCDFs was derived from some kinds of incinerations and herbicides applied in the past and that Co-PCB pollution was caused by PCB preparation used in the past in urban and industrial areas and by municipal waste incineration in urban areas.     

Relationship of PCDD/F and Co-PCB concentrations in breast milk with infant birthweights in Tokyo, Japan

OBJECTIVE: To observe how PCDD/F and Co-PCB concentrations in breast milk relate to infant birthweights in Tokyo, Japan. STUDY DESIGN: Breast milk samples were collected from 240 mothers (aged 25-34years old) residing in Tokyo to measure the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs; 14 congeners), polychlorinated dibenzofurans (PCDFs; 15 congeners), and coplanar polychlorinated biphenyls (Co-PCBs; 12 congeners) in the breast milk fat. Individual milk samples (about 50ml) were obtained 30days after delivery, between the months of June and September in 1999 and 2000. The relationship of the infant birthweights with the PCDD/F and Co-PCB concentrations was observed. RESULTS: The birthweights were negatively correlated the concentrations of many of the PCDD/F and Co-PCB congeners, with the mean toxic equivalent quantities (TEQs) of the Co-PCBs, and with the sum of the PCDD, PCDF and Co-PCBs, although their correlation coefficients were less than 0.200. Multiple regression analysis showed octachlorodioxin was statistically significant explanatory variate. CONCLUSIONS: There were slight relationship between the dioxins levels of breast milk and the birthweights of the infants.     

Correlation coefficients between the dioxin levels in mother's milk and the distances to the nearest waste incinerator which was the largest source of dioxins from each mother's place of residence in Tokyo, Japan

BACKGROUND: To observe the relationship between the PCDD/F and Co-PCB levels in samples of human breast milk and nearby waste incinerators in Tokyo, Japan. METHODS: Breast milk was taken from 240 mothers residing in Tokyo, Japan to measure and analyze the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs; 14 congeners), polychlorinated dibenzofurans (PCDFs; 15 congeners), and coplanar polychlorinated biphenyls (Co-PCBs; 12 congeners) contained in the fat. Individual milk samples (about 50 ml) were obtained from the mothers 30 days after delivery, between the months of June and September in 1999 and 2000. A map of Tokyo was used to measure the distances between each mother's place of residence and the closest public and industrial waste incinerators. RESULTS: The distances to the nearest waste incinerators bore no apparent correlations with the congeners of PCDD/Fs and Co-PCBs. The distances were also uncorrelated with the mean toxic equivalent quantities (TEQs) of PCDD/Fs (the sum of PCDDs and PCDFs), Co-PCBs, and the total PCDD/Fs and Co-PCBs. CONCLUSIONS: Although waste incinerators were the largest source of dioxins in Japan at the time of the study, the dioxins levels of mother's milk bore no apparent relationships with the distances between the mothers' domiciles and the nearest waste incinerators. In this study, several meaningful factors were not taken into account, namely, the wind direction, the level of dioxin emitted from each incinerator, the level of environmental pollution of dioxins, and the average time the mothers stayed at home each day. A full understanding of these points awaits future studies.     

Concentrations of PCDD/PCDF in soil close to a secondary aluminum smelter

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) were analyzed in samples of the emissions from a secondary aluminum smelter (ALS) and soil samples around the plant. The purpose was to estimate the impact of the emissions on the surrounding environment.PCDD/F soil concentrations were higher in the proximity of the plant, exceeding the limit adopted in Italy in soils for green areas and residential uses and the upper limit of several reference concentrations. The most contaminated sites were less than 500 m from the plant and the dioxin concentration with the distance from the ALS.Principal component analysis (PCA) showed that emissions from the ALS were the source of PCDD/F contamination in the soils closest to the plant. Multivariate data analyses such as PCA are therefore useful to identify sources of emission causing contamination.     

Concentrations of PCDD/PCDF in soil close to a secondary aluminum smelter

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) were analyzed in samples of the emissions from a secondary aluminum smelter (ALS) and soil samples around the plant. The purpose was to estimate the impact of the emissions on the surrounding environment.PCDD/F soil concentrations were higher in the proximity of the plant, exceeding the limit adopted in Italy in soils for green areas and residential uses and the upper limit of several reference concentrations. The most contaminated sites were less than 500 m from the plant and the dioxin concentration with the distance from the ALS.Principal component analysis (PCA) showed that emissions from the ALS were the source of PCDD/F contamination in the soils closest to the plant. Multivariate data analyses such as PCA are therefore useful to identify sources of emission causing contamination.     

Patterns and sources of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in surficial sediments of Lakes Erie and Ontario

This study determines spatial trends and congener patterns of 2378-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in surficial sediments of Lakes Erie and Ontario. Sediments are enriched in 2378-PCDFs in Lake Ontario, and the PCDD/F concentrations increased from shallow near-shore sediments towards deep-water depositional zone sediments. In Lake Erie, sediments were dominated by octachlorodibenzo-p-dioxin, and the highest PCDD/F concentrations were observed in the western basin and the southern shoreline of the central basin with a decrease towards the eastern basin and the northern shoreline of the central basin. Principal components analysis revealed that chemical manufacture and disposal of chemical waste along the Niagara River has been a major PCDD/F source to Lake Ontario; while PCDD/Fs in Lake Erie are from multiple sources including industrial sources along the Detroit River, major tributaries along the southern shoreline of the lake, and atmospherically-derived material from the upper lakes and connecting channels.     

PCDD/Fs in ambient air in north-east Italy: The role of a MSWI inside an industrial area

The stack gases of a municipal solid waste incinerator (MSWI), and ambient air were sampled in four locations around the plant for the analysis of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs). The sampling area was close to an industrial area near Trieste, in north-east Italy. The purpose of the study was to estimate the impact of the MSWI emissions and to distinguish the contribution of these emissions from other potential emission sources in the industrial area.PCDD/F atmospheric concentrations were similar to those generally detected in urban–rural areas with one location about 2–3 times more contaminated than the others. Since the most contaminated location was inside the industrial area but upwind of the MSWI, principal component analysis (PCA) was used to establish whether other sources were the cause. This analysis clearly showed that a local steel plant’s emission was the main source of PCDDs/Fs in ambient air. This study highlights the usefulness of multivariate data analysis such as PCA to identify, among different potential emission sources, the one really responsible for the contamination.     

Human milk survey for dioxins in the general population in Japan

BACKGROUND: Much attention has been paid to the level of dioxins in breast milk in Japan but few large-scale studies have been conducted on the subject. METHODS: From 1997 to 2002, we collected 839 samples of breast milk from primiparas residing throughout Japan. Starting in 1999, breast milk was also collected from secundiparas. Seven isomers of polychlorinated dibenzo-p-dioxins (PCDDs), 10 of polychlorinated dibenzofurans (PCDFs), 4 of coplanar polychlorinated biphenyls (Co-PCBs) and 8 of mono-orthochlorinated polychlorinated biphenyls (mono-ortho PCBs) were analyzed by employing gas chromatography and mass spectrometry. A correlation between the level of dioxins in human milk and the age of the mothers was noted for the primiparas and the secundiparas; and the levels were compared between the first and the second deliveries. Grouped by parity and prefecture in each year, observations were also made on the trends in these levels. Dioxin levels are shown by using geometric means because their distributions were skewed to the left. RESULTS: The sum of PCDDs and PCDFs, Co-PCBs, mono-ortho PCBs, and total dioxins in the breast milk of primiparas were 13.9, 5.4, 3.4, and 22.7 pg TEQ/g fat, respectively. In the samples obtained from secundiparas, these levels were 63-68 percents of those taken from the primiparas. The correlation coefficients between the PCDDs/DFs, Co-PCBs, mono-ortho PCBs, and total dioxins and the age of the primiparas were 0.19, 0.17, 0.36, and 0.24, respectively. All these correlations were statistically significant (p < 0.001). The positive correlations between these contaminants and the age of the secundiparas were also examined. The total dioxins as well as PCDDs/DFs, Co-PCBs, and mono-ortho PCBs in the breast milk of the primiparas declined significantly between 1998 and 2002 (regression coefficients: -0.04, -0.05, -0.03, and -0.03, respectively). However, no significant decline in these levels was observed when sorted by prefectures. CONCLUSIONS: Much attention should be paid to the age and parity of nursing mothers when investigating the relationship between the level of dioxins in breast milk and the body burden of infants.     

Formation and emission status of PCDDs/PCDFs in municipal solid waste incinerators in Korea

This study was carried out to examine the formation and the emission status of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDDs/PCDFs) in the flue gases of commercial-scale municipal solid waste (MSW) incinerators, and thus to provide the engineering data for the reduction of PCDDs/PCDFs emitted from MSW incinerators. The formation concentrations of the PCDDs/PCDFs generated at the outlet of waste heat boilers (WHB) were in the range of 1.18-29.61 ng-TEQ/N m3 (average 5.75 ng-TEQ/N m3), while the emission concentrations at the stacks were in the range of 0.026-4.548 ng-TEQ/N m3 (average 0.924 ng-TEQ/N m3). Two major 2,3,7,8-substituted congeners were 2,3,4,7,8-PeCDF and 2,3,4,6,7,8-HxCDF, and their concentrations were up to 50% and 64% of total TEQ values at the outlet of WHB and the stack, respectively. From the results of multi-regression analysis, the formation concentration of PCDDs/PCDFs could be predicted as follows with the correlation factor of r2 = 0.962: PCDDs/PCDFs (ng-TEQ/N m3) = 3.036 (Cl) + 0.094 (T1) - 0.472 (Combustibles) + 0.059 (CO) - 0.039 (THC) - 3.366 (H) + 22.157, where T1 (degrees C) is the temperature at the outlet of the WHB. Cl, Combustibles and H are given as percentages and the others are in parts per million.     

PCDDs, PCDFs, and PCBs concentrations in breast milk from two areas in Korea: body burden of mothers and implications for feeding infants

We determined breast milk concentration of polychlorinated dibenzo-p-dioxins (PCDDs)/polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) in 24 mothers living in Korea, and assessed the maternal body burden based on PCDDs/PCDFs and PCBs concentrations in breast milk and an infant intake rate through breast-feeding based on their concentration in breast milk. PCDDs/PCDFs and PCBs levels in breast milk from primipara mothers were found to be higher than those from multipara mothers. For total PCDDs/PCDFs TEQ level, 2,3,4,7,8-PeCDD was the predominant congener, and the proportion of 2,3,7,8-TCDD was less than 3% of total PCDDs/PCDFs TEQ level. For PCBs TEQ level, PCB-126 was the predominant congener. Maternal body burden levels of PCDDs/PCDFs and PCBs based on their concentrations in breast milk were 268-622 TEQ ng. The daily dioxin intakes of mothers were predicted to be 0.78-2.18 TEQ pg/kg/day for PCDDs/PCDFs and 0.34-0.66 TEQ pg/kg/ day for PCBs. For the first year, the body burden of an infant was predicted to be 212 TEQ ng and the daily intake of an infant was predicted to be 85 TEQ pg/kg/day, assuming the mean dioxin-related compounds concentration (27.54 TEQ pg/g fat).     

Formation of dioxin analogs by open-air incineration of waste wood and by fire of buildings and houses concerning Hanshin Great Earthquake in Japan

Ash samples were collected from site of open-air incineration and fire concerning Hanshin Great Earthquake which occurred in western Japan in the early morning of 17 January 1995. The average concentrations of total sum of PCDDs, PCDFs and Co-PCBs in ash collected from wood scrap of broken building fire site, house fire site, shoe-making factory fire site and electric appliances store fire site were 541, 442, 859 and 22,800 pgTEQ/g, respectively. Particularly, PCDFs among dioxin analogs generated remarkably at sites with a high TEQ. In addition, 79,000 t of ash was totally produced at five open-air incineration sites, and consequently the formation amount of PCDDs, PCDFs and Co-PCBs was estimated to be 70.7 gTEQ on the basis of these analytical data.     

Assessment of human exposure to PCDDs,PCDFs and Co-PCBs using hair as a human pollution indicator sample I: Development of analytical method for human hair and evaluation for exposure assessment

Dioxins including polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and co-planar polychlorinated biphenyls (Co-PCBs) are highly toxic. Even at environmental pollution levels, they cause hormonal damage in women, and they have been shown to induce immunosuppression and genital function damage in humans. In this study, a new method using isotope dilution was established to detect PCDDs, PCDFs and Co-PCBs in human hair. This method, comprised of washing and cutting of hair, alkaline decomposition, hexane extraction, multilayer silica gel column chromatography, high performance liquid chromatography with a porous graphite carbon column and analysis by high resolution gas chromatography/high resolution mass spectrometry, enabled us to analyze PCDDs, PCDFs and Co-PCBs at trace levels of less than pg/g with good reproducibility. In addition, there was a correlation between some isomers in human hair and blood collected from identical donors. Human hair analysis is useful to evaluate human risk assessment including that due to environmental pollution.     

A simplified clean-up procedure for the rapid determination of PCDDs and PCDFs based on retention on activated carbon AX-21

Different 2,3,7,8-substituted polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs) were investigated for their retention behaviour on a disposable minicolumn containing activated carbon AX-21. Elution behaviour and recovery were examined, using native and radiolabelled PCDD and PCDF isomers.

A comparison of the total mass chromatograms of PCDDs and PCDFs in an extract from animal adipose tissue, before and after activated carbon treatment, demonstrates the efficiency of this cleanup step with respect to the elimination of interfering compounds.     

Peak identification for PCDD/Fs in environmental samples at different temperature programs

A method has been developed for peak recognition of 136 polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) at different temperature programs. Their retention behaviours are predicted on the basis of an identification database of retention values (A, B) of gas chromatography. By the retention times of 13C labelled 2,3,7,8-substituted PCDD/F internal standards, the retentions of all PCDDs and PCDFs can be calculated. After comparison with the retentions of practical environmental samples, the predicted values have been proved to be very accurate.     

Atmospheric concentrations of PCDDs/PCDFs in southern California.

A comprehensive air toxics measurements program designed to establish baseline concentrations of atmospheric polychlorinated dioxins and dibenzofurans (PCDDs/PCDFs) in the South Coast Air Basin has been completed. The program utilized state-of-the-art air sampling and laboratory analysis techniques (HRGC/HRMS) to quantify the fifteen 2,3,7,8-substituted PCDDs/PCDFs congeners of primary toxicological significance. This study, which included nine discrete sampling sessions between December 1987 and March 1989, provides the first systematic assessment of ambient PCDDs/PCDFs concentrations in the state of California. The highest PCDDs/PCDFs concentrations noted during this study occurred in December 1987. This period was dominated by off-shore air flows, suggesting a regional air mass and transport phenomena. Concentrations of the PCDDs/PCDFs were diminished markedly in subsequent sampling sessions where air flow patterns were primarily of on-shore or of coastal origin. Ambient PCDDs/PCDFs concentrations, expressed as toxic equivalents, were highest during the December 1987 sampling period. The El Toro monitoring site, located approximately 40 miles southeast of Los Angeles, consistently showed the lowest measured ambient PCDDs/PCDFs concentrations and toxic equivalents values. In the majority of the sessions and samples examined the PCDDs/PCDFs congener profiles strongly suggest combustion source influences. Typical of combustion source profiles, 1,2,3,4,6,7,8-HpCDD was the predominant 2,3,7,8-substituted species and most prevalent PCDD after OCDD. The congener of highest toxicological significance, 2,3,7,8-TCDD, was reported below the 10-20 fg/m3 detection limit for most of the ambient air samples selected for analysis.     

Dibenzo-p-dioxins in the environment from ceramics and pottery produced from ball clay mined in the United States

Processed ball clay samples used in the production of ceramics and samples of the ceramic products were collected and analyzed for the presence and concentration of the 2,3,7,8-Cl substituted polychlorinated dibenzo-p-dioxins and -furans (PCDDs/PCDFs). The processed ball clay had average PCDD concentrations of 3.2 ng/g toxic equivalents, a congener profile, and isomer distribution consistent with those found previously in raw ball clay. The PCDF concentrations were below the average limit of detection (LOD) of 0.5 pg/g. The final fired ceramic products were found to be free of PCDDs/PCDFs at the LODs. A consideration of the conditions involved in the firing process suggests that the PCDDs, if not destroyed, may be released to the atmosphere and could represent an as yet unidentified source of dioxins to the environment. In addition, the PCDDs in clay dust generated during manufacturing operations may represent a potential occupational exposure.     

Apportionment of TEQs from four major dioxin sources in Japan on the basis of five indicative congeners

The major sources of dioxins (polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DL-PCBs)) in the environment in Japan have been considered to be combustion by-products, pentachlorophenol (PCP) formulations, chlornitrofen (CNP, 4-nitrophenyl-2,4,6-trichlorophenyl ether) formulations, and PCB products. Data on PCDDs, PCDFs and DL-PCBs from the four sources were analyzed, and indicative congeners whose concentrations were highly correlated with WHO-2006 toxic equivalencies (TEQs) were identified for each source sample. The indicative congeners for combustion by-products, PCP formulations, and CNP formulations were 2,3,4,7,8-pentachlorodibenzofuran, 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin, and 1,2,3,7,8-pentachlorodibenzo-p-dioxin, respectively; for PCB products, the indicative congeners were IUPAC Nos. #126- and #105-pentachlorobiphenyls. Moreover, using the data on PCDDs, PCDFs and DL-PCBs, we developed a set of equations for estimating the apportionment of TEQs from the four sources by using only the concentrations of the above-mentioned five indicative congeners. The equations were used along with the analysis results of different types of environmental samples collected from Japan, to determine the TEQ contributions of the four sources. The obtained values of TEQ contributions seemed to be reasonable. The estimation method was developed by using the data on major dioxin sources in Japan, and therefore, it is generally adaptable to environmental samples from any part of Japan. The method may be usable for regions outside Japan if source identification is carried out and the estimation equations are modified appropriately.