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Evaluation of 2,3,7,8 TCDD and PCDDs in fly ash from refuse incinerators
Chemosphere, Vol.16, Nos.8/9, pp 1865-1~68,1987 Printed in Great Britain
0045-6535/87 $3.00 + .00 Pergamon Journals Ltd.
EVALUATION OF 2,3,7,8 TCDD AND PCDDs IN FLY ASH FROM REFUSE INCINERATORS
Masaru
Tanaka
and
Ryuzo
Takeshita*
Department of Sanitary Engineering, The Institute of Public Health, Shiroganedai 4-6-I, Minato-ku, Tokyo 108 Japan, Faculty of Pharmaceutical Science*, Toho University, Miyama 2 - 2 - 1 F u n a b a s h i City, Chiba 274 Japan
I. Studies on Dioxin Generation Related to M.S.W. Governmental studies on dioxin related to Municipal Solid Waste (MSW) have been conducted for several years in Japan. Table I shows the history of dioxin studies related to M.S.W. In response to inquiries about dioxin by a number of municipalities, a study of pertinent documents was initiated in 1980. Since 1982, the laboratory has been carrying on a full scale investigation of dioxin. The first project "the behavior of trace hazardous materials during solid waste treatment and disposal" started in 1982. The purpose of the study is to evaluate the separation and extraction methods and to establish the analytical method for polychlorinated dibenzo-p-dioxins(PCDDs), particularly for 2,3,7,8-tetrachloro dibenzo-p-dioxin(TCDD) contained in fly ashes and bottom ashes. The different methods for TCDD extraction were compared and evaluated experimentally. The proposed analytical method is shown in Figure I. The 2,3,7,8-TCDD in fly ashes and bottom ashes sampled from MSW incineration plants was determined. In one of five ash samples, 2,3,7,8-TCDD was detected at a level of 1.96 ng/g. Five homologues of PCDDs in five fly ash samples from MSW incineration plants were analyzed. Concentration range of Tetra-CDD, Penta CDD, Hexa-CDD, Hepta-CDD and Octa-CDD were 0.056-30ng/g, 0.26-72ng/g, 2.0-72ng/g, 0.49-59ng/g and 10-50ng/g respectively. The second project "the emergency inspection/investigation about dioxin, mercury, trichlene, etc." was started just after major newspapers' publicity about dioxin detection in fly ash and bottom ash sampled from MSW incineration plants. This project was executed by the Institute of Public Health, the Ministry of Health and Welfare and Environmental Agency in 1984. The major objective is to investigate dioxin levels in fly ash and bottom ash of MSW incinerators and air and soil in and near MSW disposal facilities in Japan. Meanwhile the expert committee was organized to assess risks associated to dioxin generated by M.S.W. incinerators. Based on the recommendation of the Table -I 981 1982-1984 Nov.1983 Dec.1983 -May 1984 1984
1985-1989
I.
History of Governmental Studies Municipal Solid Waste in Japan
on
Dioxin Related
Mainly Literature Survey First Pro~ect: The Behavior of Trace Hazardous Materials During Solid Waste Treatment and Disposal ( by The Institute of Public Health) Newspaper Publicity of Dioxin Detection in Fly Ash and Botton Ash Expert's Committee was organized to Conduct Risk Assessment for Dioxin Generated from MSW incinerators Second Project: The Emergency Inspection/ Investigation about Dioxin, Mercury, Trichlene, etc. ( by The Institute of Public Health, Ministry of Health and Welfare, Environmental Agency) Third Pro~ect: The formation and Decomposition Mechanisms of Dioxins and Related Compounds ( by The Institute of Public Health, Ministry of Health and Welfare and National Institute of Agro-Environmental Sciences) 1865
1866 committee, the third r e s e a r c h project "the f o r m a t i o n and d e c o m p o s i t i o n m e c h a n i s m s of dioxins and related c o m p o u n d s " has been i n i t i a t e d and conducted by the Minis t r y of Health and W e l f a r e g r o u p and N a t i o n a l I n s t i t u t e of A g r o - E n v i r o n m e n t a l Science group. The o b j e c t i v e s of this study are to study effects of operating conditions of i n c i n e r a t o r s to g e n e r a t i o n of d i o x i n s and to d e v e l o p the control technique for dioxins g e n e r a t e d in refuse i n c i n e r a t o r s by studing movement of dioxins in fly ash d i s p o s e d of by landfill. The purpose of this i n v e s t i g a t i o n has been to analyze the e m i s s i o n of trace hazardous substances i n c l u d i n g d i o x i n s from m u n i c i p a l i n c i n e r a t o r s and study the g e n e r a t i o n mechanism. In 1984, overall investigation for d i o x i n from refuse incinerators were conducted. Two s t o k e r - t y p e i n c i n e r a t o r s from which c o n c e n t r a t i o n of PCDDs in flue gas are r e l a t i v e l y high were selected and i n v e s t i g a t e d for emission of dioxins on normal o p e r a t i o n for 3 days in 1985. The PCDDs in fly ash from MSW Fly LAsh i n c i n e r a t o r s were m e a s u r e d in each I 2N HCI Treatment I project and those are shown in I i Table 2. Solution Residue 2.
E v a l u a t i o n of Dioxin G e n e r a t e d Extraction Soxhlet's Extraction by MSW I n c i n e r a t o r s with Benzene with Benzene In 1983, the report in major n e w s p a p e r s on d e t e c t i o n of dioxins Benzene I Solutlon in fly ash and b o t t o m ash from Washing with IN NaOH Solution/ refuse i n c i n e r a t o r s made citizens Washing with conc. H SO worry about environmental pollution and made difficult to Extract ! site waste m a n a g e m e n t facilities. Silica Gel Colum~ Chromatography After the report, the Expert's Committee Dealing with Dioxin I Elution with n-Hexane Arising from Waste Disposal was established in the W a t e r Supply Eluate and Environmental Sanitation I Department of the Ministry of Alumina Column Chromatography Health and Welfare. Elution with 50% CH C1 The committee collected as in n-Hexane many d o c u m e n t s as p o s s i b l e w i t h i n a limited time, studied them and Elu te concluded that at the current stage, dioxin at waste disposal Concentration sites have no effect on the h e a l t h Residue of citizens in general and the individuals working at refuse LiChrosorblSi 60 HPLC incineration plants. Figure 2. shows the flow of actions taken and information to deal with D i o x i n Issue related to MSW. The committee evaluated the GC/MS GC/MS effect on the health of for PCDDs for 2,3,7,8-TCDD inhabitants in an area with the m a x i m u m annual average g r o u n d l e v e l concentration which was e s t i m a t e d Figure I Proposed Analytical Procedure of 2,3,7,8-TCDD assuming TCDDs in the dust in an and PCDDs in Fly Ash. exhaust gas to be equal to the
LiChrosoib p-18 .PLC
Table 2. PCDDs in Fly Ash from MSW Incinerators
First Project (1984) Second Project (1984) Third Project (1985)
2,3,7,8 T4CDD -TCDD ND(0.05) 0.056 ~- 1 . 9 6 "~ 30 ND ~. 4.7
~
PsCDD
H&CDD
0.26 ~-
72
H~CDD
2.0 "~
72
08CDD
0.49 r--
59
(ng/g)
10 ~
50
ND 14.5
ND(0.01) ND(0.1) ND(0.1) 1.06 ~ 12 "~" 50
PCDDs 13 r~. 267 2.7 10,700
~
0.2 71
0.7 ~- 64
1.6 "~ 43
Samples 5 35
15 130
18
1867 highest TCDD concentration in fly ash ever measured in Japan. A reference value of 0.0001 ug/kg/day for 2,3,7,8-TCDD was adopted for the purpose of assessing and managing risk caused by the dioxin from waste disposal by reference to the allowable daily intake (ADI) and other figures. The effect on the health of workers at incineration plants was also evaluated similarly. The risk assessment conducted by the committee will be outlined as follows, (I) Hazard Identification Here, 2,3,7,8-TCDD which was attracting much attention from the public and was believed to be most toxic, was singled out for evaluation and study. However, the reported maximum quantity of TCDDs contained in fly ash was adopted as the total quantity of dioxin. The degree of toxicity of dioxin varies with the isomer. Among all PCDDs subjected to toxicity assessment, 2,3,7,8-TCDD has outstanding toxicity. It has an extremely low value of acute toxicity LD50 against experimental animals in comparison with the other PCDDs. The effects on health of all varieties of PCDDs were assessed by suing TCDDs which are smaller in quantity than PCDDs, by way of study of the effect on health of dioxin. The toxicity was judged to be equivalent to that of 2,3,7,8-TCDD. (2) Exposure Assessment for People in General First, assuming that in exhaust gas TCDDs are adsorbed to particulate matters and composition of TCDDs which reach to the ground surface is the same as that in exhaust gas. And assuming that the exhaust gas concentration of particulate matter is to be the maximum limit under the Air Pollution Control Law (0.5 g/Nm 3 as dust and soot) and the concentration of TCDDs in the particulate matters are the same as that of fly ash. The concentration of fly ash's TCDDs varies very much along with sampling conditions, analysis conditions, etc. But here, 250 ng/g of fly ash, the largest concentration so far reported is used. Then, the concentration of TCDDs in exhaust gas would be; 250ng/g x 0.5 g/NmJ=125 ng/Nm 3 However, the concentration of PCDDs in particulate matters of emission gas is assumed, for the sake of safety, to be ten times larger than that in fly ash, then, 1,250 ng/Nm s is calculated. The hourly maximum surface concentration could be calculated with dispersion rate of 5000. The yearly average maximum surface concentration is assumed to be 1/40 of the hourly maximum, and 6.3 x 10 -3 ng/Nm ~ was calculated for the yearly maximum surface concentration. Requlator Experts (3) Exposure Assessment for Workers in MSW Incinerators The first assumption is that all dusts in working environment come from fly ash. And so far as ordinary workers at plants are concerned, the largest concentration of dust is assumed to be 0.51 mg/Nm3in the basement of a furnace. As for inspection within a furnace, the concentration is assumed to be 44.3 mg/Nm~which was actually measured in incineration plants. With these data and the largest concentration of TCDDs' concentration in fly ash (250 ng/g), TCDDs concentration at working environment could be calculated; 0.127ng/m 3 for ordinary work, and 11.075 ng/m 3 for inspection in a furnace. (4) Dose-Response Assessment Based on the 2,3,7,8-TCDD's NOEL of 0.001 pg/kg/day by U.S.E.P.A. Science Advisory Panel in 1980, considering the ADI of 0.0001 ~g/kg/day by National Academy of Science in 1977, and the report of Nisbet,
Figure 2 Actors Involved in Risk Management for Dioxin Contained in Fly Ash Generated from MSW
1868
et al. in 1982 that 0 . 0 0 1 p g / k g / d a y is still an effect level, the e v a l u a t i o n guideline( so called VSD) as to dioxin p r o b l e m from the view point of management, was set to be 0.0001 pg/kg/day.
waste
(5) Health Risk E v a l u a t i o n for People in General It is a s s u m e d that the volume of r e s p i r a t i o n of a man is 15 m a /day (average weight:60kg) and all TCDDs in the b r e a t h e d air are absorbed. Then the amount of TCDDs absorbed by ~the people in general would be; 6.3 x 10 -~ n g / N m ~ x 15 ma /day/60kg= 1.58 x I O'ng/kg/day. This amount is smaller than the Evaluation Guideline. Since, in this estimation, TCDDs' intake is c o m p a r e d with the e v a l u a t i o n g u i d e l i n e of 2,3,7,8TCDD, in the actual situation, it w o u l d give further safety. (6) Health Risk E v a l u a t i o n for Workers in MSW Incinerators It is assumed that the volume of r e s p i r a t i o n of a worker d u r i n g 8 working hours is 10 m ~ ( a v e r a g e weight:60kg), yearly work days are 300, and all TCDDs in the breathed air are absorbed. The amount of TCDDs a b s o r b e d by workers in waste incineration plants for w o r k i n g hours would be 0.0174 ng/kg/day. Assuming, a furnace is inspected once a year for 5 days, and the i n s p e c t i o n w o r k e r does not put on a dust mask, the amount of absorbed TCDDs would be at most 0.025ng/kg/day. When a worker in the plant also inspect the furnace, assuming the volume of r e s p i r a t i o n out of w o r k i n g hours is 10m 3 , the total amout of TCDDs' intake of the worker would be 0.044ng/kg/day. This is smaller than the Evaluation Guideline.
The report on the d e t e c t i o n of d i o x i n in the residue from waste d i s p o s a l plants had various repercussions. The d i o x i n p r o b l e m should be r e c o g n i z e d as something that casts doubt about the f u n d a m e n t a l v a l i d i t y of the conventional waste disposal method, and there is a need to take suitable a c t i o n in respect of chemicals and carry out the needed risk a s s e s s m e n t and risk management.
Reference: I. Masaru Tanaka, et al.: The B e h a v i o r of Trace H a z a r d o u s M a t e r i a l s During Solid Waste T r e a t m e n t and Disposal, E n v i r o n m e n t a l R e s e a r c h in Japan, 1982, 1983 and 1984, by National Research Institutes of G o v e r n m e n t Ministries & Agencies, E n v i r o n m e n t a l Agency. 2. Masaru Tanaka, et al.: A Study on the F o r m a t i o n and D e c o m p o s i t i o n M e c h a n i s m s of Dioxins and Related Compounds, Environmental Research in Japan, 1985, by N atio n a l R e s e a r c h Institutes of G o v e r n m e n t M i n i s t r i e s & Agencies, Environmental Agency.
0045-6535/87 $3.00 + .00 Pergamon Journals Ltd.
EVALUATION OF 2,3,7,8 TCDD AND PCDDs IN FLY ASH FROM REFUSE INCINERATORS
Masaru
Tanaka
and
Ryuzo
Takeshita*
Department of Sanitary Engineering, The Institute of Public Health, Shiroganedai 4-6-I, Minato-ku, Tokyo 108 Japan, Faculty of Pharmaceutical Science*, Toho University, Miyama 2 - 2 - 1 F u n a b a s h i City, Chiba 274 Japan
I. Studies on Dioxin Generation Related to M.S.W. Governmental studies on dioxin related to Municipal Solid Waste (MSW) have been conducted for several years in Japan. Table I shows the history of dioxin studies related to M.S.W. In response to inquiries about dioxin by a number of municipalities, a study of pertinent documents was initiated in 1980. Since 1982, the laboratory has been carrying on a full scale investigation of dioxin. The first project "the behavior of trace hazardous materials during solid waste treatment and disposal" started in 1982. The purpose of the study is to evaluate the separation and extraction methods and to establish the analytical method for polychlorinated dibenzo-p-dioxins(PCDDs), particularly for 2,3,7,8-tetrachloro dibenzo-p-dioxin(TCDD) contained in fly ashes and bottom ashes. The different methods for TCDD extraction were compared and evaluated experimentally. The proposed analytical method is shown in Figure I. The 2,3,7,8-TCDD in fly ashes and bottom ashes sampled from MSW incineration plants was determined. In one of five ash samples, 2,3,7,8-TCDD was detected at a level of 1.96 ng/g. Five homologues of PCDDs in five fly ash samples from MSW incineration plants were analyzed. Concentration range of Tetra-CDD, Penta CDD, Hexa-CDD, Hepta-CDD and Octa-CDD were 0.056-30ng/g, 0.26-72ng/g, 2.0-72ng/g, 0.49-59ng/g and 10-50ng/g respectively. The second project "the emergency inspection/investigation about dioxin, mercury, trichlene, etc." was started just after major newspapers' publicity about dioxin detection in fly ash and bottom ash sampled from MSW incineration plants. This project was executed by the Institute of Public Health, the Ministry of Health and Welfare and Environmental Agency in 1984. The major objective is to investigate dioxin levels in fly ash and bottom ash of MSW incinerators and air and soil in and near MSW disposal facilities in Japan. Meanwhile the expert committee was organized to assess risks associated to dioxin generated by M.S.W. incinerators. Based on the recommendation of the Table -I 981 1982-1984 Nov.1983 Dec.1983 -May 1984 1984
1985-1989
I.
History of Governmental Studies Municipal Solid Waste in Japan
on
Dioxin Related
Mainly Literature Survey First Pro~ect: The Behavior of Trace Hazardous Materials During Solid Waste Treatment and Disposal ( by The Institute of Public Health) Newspaper Publicity of Dioxin Detection in Fly Ash and Botton Ash Expert's Committee was organized to Conduct Risk Assessment for Dioxin Generated from MSW incinerators Second Project: The Emergency Inspection/ Investigation about Dioxin, Mercury, Trichlene, etc. ( by The Institute of Public Health, Ministry of Health and Welfare, Environmental Agency) Third Pro~ect: The formation and Decomposition Mechanisms of Dioxins and Related Compounds ( by The Institute of Public Health, Ministry of Health and Welfare and National Institute of Agro-Environmental Sciences) 1865
1866 committee, the third r e s e a r c h project "the f o r m a t i o n and d e c o m p o s i t i o n m e c h a n i s m s of dioxins and related c o m p o u n d s " has been i n i t i a t e d and conducted by the Minis t r y of Health and W e l f a r e g r o u p and N a t i o n a l I n s t i t u t e of A g r o - E n v i r o n m e n t a l Science group. The o b j e c t i v e s of this study are to study effects of operating conditions of i n c i n e r a t o r s to g e n e r a t i o n of d i o x i n s and to d e v e l o p the control technique for dioxins g e n e r a t e d in refuse i n c i n e r a t o r s by studing movement of dioxins in fly ash d i s p o s e d of by landfill. The purpose of this i n v e s t i g a t i o n has been to analyze the e m i s s i o n of trace hazardous substances i n c l u d i n g d i o x i n s from m u n i c i p a l i n c i n e r a t o r s and study the g e n e r a t i o n mechanism. In 1984, overall investigation for d i o x i n from refuse incinerators were conducted. Two s t o k e r - t y p e i n c i n e r a t o r s from which c o n c e n t r a t i o n of PCDDs in flue gas are r e l a t i v e l y high were selected and i n v e s t i g a t e d for emission of dioxins on normal o p e r a t i o n for 3 days in 1985. The PCDDs in fly ash from MSW Fly LAsh i n c i n e r a t o r s were m e a s u r e d in each I 2N HCI Treatment I project and those are shown in I i Table 2. Solution Residue 2.
E v a l u a t i o n of Dioxin G e n e r a t e d Extraction Soxhlet's Extraction by MSW I n c i n e r a t o r s with Benzene with Benzene In 1983, the report in major n e w s p a p e r s on d e t e c t i o n of dioxins Benzene I Solutlon in fly ash and b o t t o m ash from Washing with IN NaOH Solution/ refuse i n c i n e r a t o r s made citizens Washing with conc. H SO worry about environmental pollution and made difficult to Extract ! site waste m a n a g e m e n t facilities. Silica Gel Colum~ Chromatography After the report, the Expert's Committee Dealing with Dioxin I Elution with n-Hexane Arising from Waste Disposal was established in the W a t e r Supply Eluate and Environmental Sanitation I Department of the Ministry of Alumina Column Chromatography Health and Welfare. Elution with 50% CH C1 The committee collected as in n-Hexane many d o c u m e n t s as p o s s i b l e w i t h i n a limited time, studied them and Elu te concluded that at the current stage, dioxin at waste disposal Concentration sites have no effect on the h e a l t h Residue of citizens in general and the individuals working at refuse LiChrosorblSi 60 HPLC incineration plants. Figure 2. shows the flow of actions taken and information to deal with D i o x i n Issue related to MSW. The committee evaluated the GC/MS GC/MS effect on the health of for PCDDs for 2,3,7,8-TCDD inhabitants in an area with the m a x i m u m annual average g r o u n d l e v e l concentration which was e s t i m a t e d Figure I Proposed Analytical Procedure of 2,3,7,8-TCDD assuming TCDDs in the dust in an and PCDDs in Fly Ash. exhaust gas to be equal to the
LiChrosoib p-18 .PLC
Table 2. PCDDs in Fly Ash from MSW Incinerators
First Project (1984) Second Project (1984) Third Project (1985)
2,3,7,8 T4CDD -TCDD ND(0.05) 0.056 ~- 1 . 9 6 "~ 30 ND ~. 4.7
~
PsCDD
H&CDD
0.26 ~-
72
H~CDD
2.0 "~
72
08CDD
0.49 r--
59
(ng/g)
10 ~
50
ND 14.5
ND(0.01) ND(0.1) ND(0.1) 1.06 ~ 12 "~" 50
PCDDs 13 r~. 267 2.7 10,700
~
0.2 71
0.7 ~- 64
1.6 "~ 43
Samples 5 35
15 130
18
1867 highest TCDD concentration in fly ash ever measured in Japan. A reference value of 0.0001 ug/kg/day for 2,3,7,8-TCDD was adopted for the purpose of assessing and managing risk caused by the dioxin from waste disposal by reference to the allowable daily intake (ADI) and other figures. The effect on the health of workers at incineration plants was also evaluated similarly. The risk assessment conducted by the committee will be outlined as follows, (I) Hazard Identification Here, 2,3,7,8-TCDD which was attracting much attention from the public and was believed to be most toxic, was singled out for evaluation and study. However, the reported maximum quantity of TCDDs contained in fly ash was adopted as the total quantity of dioxin. The degree of toxicity of dioxin varies with the isomer. Among all PCDDs subjected to toxicity assessment, 2,3,7,8-TCDD has outstanding toxicity. It has an extremely low value of acute toxicity LD50 against experimental animals in comparison with the other PCDDs. The effects on health of all varieties of PCDDs were assessed by suing TCDDs which are smaller in quantity than PCDDs, by way of study of the effect on health of dioxin. The toxicity was judged to be equivalent to that of 2,3,7,8-TCDD. (2) Exposure Assessment for People in General First, assuming that in exhaust gas TCDDs are adsorbed to particulate matters and composition of TCDDs which reach to the ground surface is the same as that in exhaust gas. And assuming that the exhaust gas concentration of particulate matter is to be the maximum limit under the Air Pollution Control Law (0.5 g/Nm 3 as dust and soot) and the concentration of TCDDs in the particulate matters are the same as that of fly ash. The concentration of fly ash's TCDDs varies very much along with sampling conditions, analysis conditions, etc. But here, 250 ng/g of fly ash, the largest concentration so far reported is used. Then, the concentration of TCDDs in exhaust gas would be; 250ng/g x 0.5 g/NmJ=125 ng/Nm 3 However, the concentration of PCDDs in particulate matters of emission gas is assumed, for the sake of safety, to be ten times larger than that in fly ash, then, 1,250 ng/Nm s is calculated. The hourly maximum surface concentration could be calculated with dispersion rate of 5000. The yearly average maximum surface concentration is assumed to be 1/40 of the hourly maximum, and 6.3 x 10 -3 ng/Nm ~ was calculated for the yearly maximum surface concentration. Requlator Experts (3) Exposure Assessment for Workers in MSW Incinerators The first assumption is that all dusts in working environment come from fly ash. And so far as ordinary workers at plants are concerned, the largest concentration of dust is assumed to be 0.51 mg/Nm3in the basement of a furnace. As for inspection within a furnace, the concentration is assumed to be 44.3 mg/Nm~which was actually measured in incineration plants. With these data and the largest concentration of TCDDs' concentration in fly ash (250 ng/g), TCDDs concentration at working environment could be calculated; 0.127ng/m 3 for ordinary work, and 11.075 ng/m 3 for inspection in a furnace. (4) Dose-Response Assessment Based on the 2,3,7,8-TCDD's NOEL of 0.001 pg/kg/day by U.S.E.P.A. Science Advisory Panel in 1980, considering the ADI of 0.0001 ~g/kg/day by National Academy of Science in 1977, and the report of Nisbet,
Figure 2 Actors Involved in Risk Management for Dioxin Contained in Fly Ash Generated from MSW
1868
et al. in 1982 that 0 . 0 0 1 p g / k g / d a y is still an effect level, the e v a l u a t i o n guideline( so called VSD) as to dioxin p r o b l e m from the view point of management, was set to be 0.0001 pg/kg/day.
waste
(5) Health Risk E v a l u a t i o n for People in General It is a s s u m e d that the volume of r e s p i r a t i o n of a man is 15 m a /day (average weight:60kg) and all TCDDs in the b r e a t h e d air are absorbed. Then the amount of TCDDs absorbed by ~the people in general would be; 6.3 x 10 -~ n g / N m ~ x 15 ma /day/60kg= 1.58 x I O'ng/kg/day. This amount is smaller than the Evaluation Guideline. Since, in this estimation, TCDDs' intake is c o m p a r e d with the e v a l u a t i o n g u i d e l i n e of 2,3,7,8TCDD, in the actual situation, it w o u l d give further safety. (6) Health Risk E v a l u a t i o n for Workers in MSW Incinerators It is assumed that the volume of r e s p i r a t i o n of a worker d u r i n g 8 working hours is 10 m ~ ( a v e r a g e weight:60kg), yearly work days are 300, and all TCDDs in the breathed air are absorbed. The amount of TCDDs a b s o r b e d by workers in waste incineration plants for w o r k i n g hours would be 0.0174 ng/kg/day. Assuming, a furnace is inspected once a year for 5 days, and the i n s p e c t i o n w o r k e r does not put on a dust mask, the amount of absorbed TCDDs would be at most 0.025ng/kg/day. When a worker in the plant also inspect the furnace, assuming the volume of r e s p i r a t i o n out of w o r k i n g hours is 10m 3 , the total amout of TCDDs' intake of the worker would be 0.044ng/kg/day. This is smaller than the Evaluation Guideline.
The report on the d e t e c t i o n of d i o x i n in the residue from waste d i s p o s a l plants had various repercussions. The d i o x i n p r o b l e m should be r e c o g n i z e d as something that casts doubt about the f u n d a m e n t a l v a l i d i t y of the conventional waste disposal method, and there is a need to take suitable a c t i o n in respect of chemicals and carry out the needed risk a s s e s s m e n t and risk management.
Reference: I. Masaru Tanaka, et al.: The B e h a v i o r of Trace H a z a r d o u s M a t e r i a l s During Solid Waste T r e a t m e n t and Disposal, E n v i r o n m e n t a l R e s e a r c h in Japan, 1982, 1983 and 1984, by National Research Institutes of G o v e r n m e n t Ministries & Agencies, E n v i r o n m e n t a l Agency. 2. Masaru Tanaka, et al.: A Study on the F o r m a t i o n and D e c o m p o s i t i o n M e c h a n i s m s of Dioxins and Related Compounds, Environmental Research in Japan, 1985, by N atio n a l R e s e a r c h Institutes of G o v e r n m e n t M i n i s t r i e s & Agencies, Environmental Agency.