The Science of the Total Environment, 104 (1991) 87-96 Elsevier Science Publishers B.V., Amsterdam
87
Air emissions from municipal waste combustion and their environmental effects A. Roffman and H.K. Roffman A WD Technologies Inc., Penn Center West, Bldg III, Suite 300, Pittsburgh, PA 15276, USA
ABSTRACT This paper addresses risk-assessment estimates associated with air emissions from MWC facilities via the inhalation pathway. Calculations performed address selected chemical constituents with the potential highest human health effects. The calculated carcinogenic risks are small and are well below the EPA acceptable risk of 10-4. Similarly, the calculated noncarcinogenic risks are well below the acceptable reference dose values. Calculations presented in this paper for selected constituents could be expanded to additional chemical constituents. INTRODUCTION Forecasts related to municipal solid waste (MSW) indicate an expected steady increase in volume, coupled with a corresponding decrease in the capacity of approved landfills. This issue has surfaced in many presentations and articles, with the prime concern being how to best deal with the situation. One o f the attractive alternatives for reducing the volume of M S W is burning it in municipal waste combustion ( M W C ) facilities. This approach has been adopted by many municipalities and local communities. It is anticipated that the number of M W C facilities in the USA, which now exceeds 100, m a y reach a b o u t 300 by the turn of the century. The increase in the number o f M W C facilities has increased the public concern a b o u t the potential environmental effects o f such facilities resulting from air emissions, discharges to water bodies, and the disposal o f generated ashes on land. This paper presents an analysis of the effects of air emissions from M W C facilities on the public health via inhalation. The analysis was performed for selected metals and organic constituents. The effects are expressed as excess cancer risks for carcinogenic constituents and as noncarcinogenic risks for noncarcinogenic constituents. The calculations provided in this paper are based on emission data presented in the U.S. Environmental Protection Agency (EPA) Municipal Waste C o m b u s t i o n Study [1], which is based on data compiled from existing facilities. Stack heights used in the calculations are 200-300
0048-9697/91/$03.50
© 1991 - - Elsevier Science Publishers B.V.
88
A. ROFFMAN AND H.K. ROFFMAN
feet*. These heights represent stack heights for new facilities and are in line with the Good Engineering Practices (GEP) stack-height regulations promulgated by the EPA [2]. Results of the calculations conducted for the selected constituents indicate that The estimated carcinogenic and noncarcinogenic risks resulting from air emissions from MWC facilities via the inhalation pathway are several orders of magnitude below the results presented in the EPA Municipal Waste Combustion Study [1]. - - The estimated carcinogenic risks are several orders of magnitude below the EPA generally accepted health risk level of 10 - 4 . The major differences between the calculations performed in this paper and those performed in the EPA study are rooted in several overconservative assumptions included in the EPA study. For example, the EPA report unrealistically assumes low stack heights for proposed new facilities. Such low stack heights would not pass the scrutiny of the EPA GEP regulations. Additional conservatism embedded in the EPA calculations is attributed to the emission rates for the constituents involved especially since the calculations are for proposed new facilities. Risk-assessment calculations were performed for selected constituents, including arsenic, cadmium, lead, and 2,3,7,8-tetrachlorodibenzodioxin (2,3,7,8-TCDD). These calculations can be expanded to include additional constituents by merely performing the appropriate scaling calculations. -
-
METHODOLOGY
A key input to the risk-assessment calculations is the calculated air concentrations of the selected constituents that are derived by one of the EPA air-quality guidelines dispersion models. Input data that drive the dispersion model include emission rates and stack parameters, meteorology, and a receptor grid representing the locations for which calculations are performed. Air-emission rates used in these dispersion calculations were derived from emission information provided in the EPA Municipal Combustion Study [1]. This reference report provides lowest and highest reported emission levels for mass burn, modular, and refuse-derived fuel (RDF) facilities. Table 1 provides the lowest and highest emission concentrations for arsenic, cadmium, lead, and 2,3,7,8-TCDD for the three types of MWC facilities. The emission concentrations were converted to emission rates, using data provided in ref. 1, and summarized in Table 2. The data presented in Table 2 are used in the dispersion calculations. *1
foot =
0.305m.
Munich Nalmo Marion County Wurzburg WSH/DI/FF
SD/FF
CYC/DI/ESP/FF
ESP/SD
0.018
452 6220 2.51 ×
l0 4
Hampton
Hampton Hampton Braintree
Facility name
Concentration (ngNm 3)
Facility name
Air pollution control
Highest emission
Lowest emission
ESP
ESP ESP ESP
Air pollution control
62.5
2.33 × 105 5.0 x 105 1.54 × 10 7
Concentration (ngNm -3)
Red Wing
2.3,7,8-TCDD
ESP
ESP
ESP
No pollution control ×
10 4
0.278
2.37 × 105
2.09
6090
Prince Edward Island Prince Edward Island Dyersburg
Tuscaloosa
No pollution control
No pollution control
No pollution control
ESP
1.54
1.55 x 107
9.42 × 105
1.19 × 10 -5
Albany Albany Albany Albany
ESP ESP ESP ESP
1.91 × 10 4 3.37 × l 0 4 9.73 x 10s 0.522
Akron Akron Akron Akron
ESP ESP ESP ESP
1.6 x 105 3.73 x 105 9.6 x 106 14.6
From US EPA Municipal Waste Combustion Study, EPA/530-SW-87-021b, June 1987. Nm -3, m 3 at normal conditions of 1 atmosphere and 20°C; ESP, electrostatic precipitator; SD, spray dryer; CYC, cyclone; DI, dry injection; FF, fabric filter; WSH, water spray humidifier.
Arsenic Cadmium Lead 2,3,7,8-TCDD
Municipal waste combustor facilities metals and organic constituents emission concentrations used in the calculationsa for refuse-derived fuel facilities
Barron County
Prince Edward Island Barron County
Lead
Cadmium
Arsenic
Municipal waste combustor facilities metals and organic constituents emission concentrations used in the calculationsa for modular facilities
2,3,7,8-TCDD
Arsenic Cadmium Lead
Constituent
Municipal waste combustor facilities metals and organic constituents emission concentrations used in the calculationsa for mass burn facilities
TABLE 1
OO
90
A. R O F F M A N A N D H.K. R O F F M A N
TABLE 2 Constituent emission rates used in calculationsa Constituent
Arsenic Cadmium Lead 2,3,7,8TCDD
Emission rate (mg h - I ) Mass burn facilities
Modular facilities
R D F facilities
5.8
6.2 x 101-9.07 x l03 1.55 x 102-9.55 x 103 1.81 x 103-1.22 x 105 0.02~).02
2,51 x 103-1.33 x 104 4.43 x 103-3.11 × 104 1.28 x 105-8.0 x 105 0.07- 1.22
x 101-5.06 x 103 2.8-1.09 x 104 1.57 x 103-5.47 x 105 0.0009- 1.36
aBased on measured data reported in the US EPA, Municipal Waste Combustion Study, EPA/530-SW-87-021b, June 1987.
It should be noted that the emission rates presented in Table 2 are based on measurements at existing facilities equipped with various types of airpollution control devices. These emissions do not necessarily represent stateof-the-art air-pollution control for new M W C facilities. This implies that the emission rates in Table 2 could represent conservative upper-limit emissions. Stack parameters, including stack exit diameters, exit temperatures, and exit velocities, were obtained from refs. 1 and 3. Stack heights used in the calculations were for facililites with 200- and 300-foot stacks. These heights were selected based on information obtained from owners of MWC facilities and represent present design for new facilities. The selected heights are higher than those used in the EPA Municipal Waste Combustion Study [3,5]. Meteorological data employed in the dispersion calculations included a STAR (STability ARay) tabulation of meteorological data consisting of the annual frequency distribution of wind speed and direction by atmospheric stability classes for a selected meteorological weather station. Key features of the meteorological data base are - - Predominant wind direction sectors are west-northwest, northwest, northnorthwest, and north (41.3 % of the time) and south-southwest and southwest (19.9% of the time) Atmospheric stability conditions determined by the use of sigma theta classifications indicate about 41% of neutral atmospheric conditions and 23% of stable atmospheric conditions. The industrial source complex (ISC) air dispersion model was used for performing annual dispersion calculations using the rural mode option. This is an EPA air-quality guideline dispersion model. Air concentrations were calculated at receptors located along the 16 cardinal wind directions on 10 concentric rings at distances of 0.5, 1.0, 1.5, 2.0, 3.0, 5.0, 7.5, 10.0, 12.5, and -
-
AIR EMISSIONS FROM MUNICIPAL WASTE COMBUSTION
91
15.0 km from the source. Maximum annual air concentrations served as input into the risk-assessment calculations. The risk-assessment methodology was based on the methodology outlined in the USEPA Superfund Assessment Manual [4] for the inhalation air pathway. The lifetime inhalation carcinogenic risk was calculated from the expression Individual excess cancer risk -- (concentration × daily inhalation rate x CPF x absorption fraction)/weight where concentration is the calculated maximum annual concentration of a constituent derived by the ISC dispersion model (/zgm-3); daily inhalation rate = 20 m 3 day-i for an adult; C P F is the carcinogenic potency factor (mg kg-I day-I), with values of 50 for arsenic, 6.1 for cadmium, and 1.56 × 105 for 2,3,7,8-TCDD; absorption fraction is the fraction of inhaled constituent that is absorbed through the lungs, assumed to be 0.5 for arsenic and cadmium and 0.55 for 2,3,7,8-TCDD; and weight is the individual's weight, assumed to be 70 kg for an adult. Lifetime risk means 24-h exposure per day over a period of 70 years. The inhalation noncarcinogenic risk was calculated from the expression. Individual noncarcinogenic risk -- (concentration × daily inhalation rate x "absorption fraction)/weight/reference dose where reference dose is the inhalation acceptable dose (mg kg-i day-l), with a value of 4.3 × l0 -4 for lead. In general, if the value of the individual noncarcinogenic risk is _< 1 it is considered an acceptable inhalation dose. RESULTS Dispersion calculations and associated risk-assessment calculations were performed using the emission rates provided in Table 2, for the four constituents of interest, the three types of MWC facilities, and two stack heights. A total of 48 computer runs were performed as part of those risk-assessment calculations. Tables 3 and 4, respectively, provide a summary of the estimated carcinogenic and noncarcinogenic risk resulting from air emissions from MWC facilities via the inhalation air pathway. The data in these tables represent maximum risk based on maximum annual calculated concentrations and lifetime exposure of 24 h per day over a lifetime of 70 years. This implies that the data in Tables 3 and 4 represent worst-case exposure scenarios. The maximum exposure risk for the 200-foot stack height occurs at a distance ranging from 500 to 1500 m from the stack, whereas the maximum exposure risk for the 300-foot stack occurs at a distance ranging from 1000 to 2000 m from the stack.
Arsenic Cadmium 2,3,7,8-TCDD
RDF
10 -9
1.8 x 10 -7 3.9 x 10 -7 1.7 x 10 -8
2.2 x 10 -8 6.1 x 10 8 2.6 x 10 -8
X
1.2 × 10 -6 3.4 x 10 -6 3.8 x 10 -7
9.3 × 1 0 - 7 4.1 x 10 6 1.9 x 10 -8
1.0 × 1 0 - 6 2.7 x 10 -6 9.5 x 10 -7
a W o r s t - c a s e e x p o s u r e is b a s e d o n 2 4 - h e x p o s u r e p e r d a y o v e r t h e a v e r a g e life o f 70 y e a r s . b U S E P A a c c e p t e d e x c e s s c a r c i n o g e n i c risk is 10 -4 ( o n e in t e n t h o u s a n d ) .
Arsenic Cadmium 2,3,7,8-TCDD
2.6 × 10 -9 4.4 × 10 - I °
Modular
4.8
Arsenic
Cadmium 2,3,7,8-TCDD
Mass burn
1.2 × 10 -7 2.5 x 10 -7 1.2 x 10 -8
1.1 x 10 -8 3.1 x 10 -8 1.2 x 10 -8
3.0 x 10 9 1.0 x 10 9 2.6 x 10 -10
Lowest reported e m i s s i o n level
Lowest reported e m i s s i o n level Highest reported e m i s s i o n level
300-foot stack height
200-foot stack height
I n d i v i d u a l e x c e s s c a r c i n o g e n i c risk ~
Constituent
Combustor type
7.7 x 10 -7 2.1 × 10 -6 2.3 x 10 -7
5.7 X 1 0 - 7 2.0 × 1 0 - 6 1.0 x 10 - s
5.4 x 10 7 1.5 × 10 -6 5.2 x 10 -7
Highest reported e m i s s i o n level
E s t i m a t e d c a r c i n o g e n i c risk r e s u l t i n g f r o m air e m i s s i o n s f r o m m u n i c i p a l w a s t e c o m b u s t o r s - - i n h a l a t i o n air p a t h w a y , w o r s t - c a s e e x p o s u r e a
TABLE 3
Z
O
Z
'7
tO
Lead Lead Lead
Mass b u r n Modular RDF
1.1 x 10 5 2.7 x 10 -5 4.3 x 10 4
Lowest r e p o r t e d emission level
200-foot stack height
4.4 x 10 3 2.2 x 10 3 3.3 x 10 .3
Highest r e p o r t e d emission level
Individual n o n c a r c i n o g e n i c risk
6.0 x 10 6 1.4 x 10 -5 2.7 x 10 4
Lowest r e p o r t e d emission level
300-foot stack height
2.5 x 10 3 1.0 x 10 3 2.1 × 10 .3
Highest reported emission level
i n h a l a t i o n air pathway, worst-case exposure"
a Worst-case exposure is based on 24-h exposure per day over the average life o f 70 years. A n o n c a r c i n o g e n i c risk is m e a s u r e d as a ratio between the calculated dose and the reference dose. A q u a n t i t y _< 1 is considered a n o n c a r c i n o g e n i c acceptable risk.
Constituent
Combustor type
Estimated n o n c a r c i n o g e n i c risk resulting from air emissions from municipal waste c o m b u s t o r s
TABLE 4
Arsenic Cadmium 2,3,7,8-TCDD
Arsenic Cadmium 2,3,7,8-TCDD
Arsenic Cadmium 2,3,7,8-TCDD
Mass burn
Modular
RDF
1.7 x 10 8 3.7 × 10 -8 1.6 × 1 0 - 9
2.1 x 10 -9 5.8 × 10 -9 2.5 × 1 0 - 9
4 . 6 x 10 - l ° 2.5 x 10 -1° 4.1 x 10 - t l
1.1 x 10 -7 3.2 × 10 7 3.6 x 10 8
9.3 × 10 8 3.9 × 10 -7 1.8 × 1 0 - 9
9.8 x 10 - s 2.6 X 1 0 - 7 9.0 x 10 -8
1.1 x 10 8 2.4 × 10 -8 1.1 × 1 0 - 9
1.0 × 10 -9 2.9 × 10 -9 1.2 × 10 -8
2.9 x 10 - l ° 9.7 x 10 -1' 2.4 x 10 - l l
Lowest reported e m i s s i o n level
Lowest reported e m i s s i o n level Highest reported e m i s s i o n level
300-foot stack height
200-foot stack height
I n d i v i d u a l e x c e s s c a r c i n o g e n i c risk b
a Realistic c a s e e x p o s u r e is b a s e d o n 8 - h e x p o s u r e p e r d a y o v e r a p e r i o d o f 20 y e a r s . b U S E P A a c c e p t e d e x c e s s c a r c i n o g e n i c risk is 10 -4 ( o n e in t e n t h o u s a n d ) .
Constituent
Combustor type
7.1 x 10 -8 2.0 × 10 -7 2.2 x 10 8
5.7 × 10 8 1.9 × 10 -7 9.0 x 10 -~°
5.3 x 10 8 1.4 × 1 0 - 7 4.9 x 10 -8
Highest reported e m i s s i o n level
E s t i m a t e d c a r c i n o g e n i c risk r e s u l t i n g f r o m air e m i s s i o n s f r o m m u n i c i p a l w a s t e c o m b u s t o r s - - i n h a l a t i o n air p a t h w a y , realistic c a s e e x p o s u r e a
TABLE 5
Lead Lead Lead
Mass b u r n Modular RDF
1.1 × 10 -6 2.6 × 10 6 4.1 × 10 -5
Lowest reported emission level
200-foot stack height
4.2 × 10 -4 2.1 × 1 0 - 4 3.2 × 10 -4
Highest r e p o r t e d emission level
Individual n o n c a r c i n o g e n i c risk a
6.0 × 10 7 1.3 × 10 6 2.6 × 10 5
Lowest r e p o r t e d emission level
300-foot stack height
2.4 × 10 4 1.0 × 10 4 2.0 × 10 4
Highest reported emission level
Realistic case exposure is based o n 8-h exposure per day over a period o f 20 years. A n o n c a r c i n o g e n i c risk is m e a s u r e d as a ratio between the calculated dose a n d the reference dose. A q u a n t i t y < 1 is considered a n o n c a r c i n o g e n i c acceptable risk.
Constituent
Combustor type
Estimated n o n c a r c i n o g e n i c risk resulting from air emissions f r o m municipal waste c o m b u s t o r s - - i n h a l a t i o n air p a t h w a y , realistic case exposure a
TABLE 6
96
A. ROFFMAN AND H.K. ROFFMAN
The USEPA acceptable individual excess carcinogenic risk for inhalation is 10 -4, o r one in 10 000 persons. The highest risk listed in Table 3 is 4.1 × 10 -6,
which is about 1/24, or 4.2% of the EPA acceptable carcinogenic risk for inhalation. Similarly, the noncarcinogenic risk figures provided in Table 4 indicate that the highest risk is 4.4 x 10 -3, about 1/227, or 0.4% of the acceptable value. Tables 5 and 6, respectively, provide a summary of estimated carcinogenic and noncarcinogenic risks resulting from air emissions from M W C facilities via the inhalation air pathway for a more realistic case. In this case an "8 hour a day" exposure over only 20 years is assumed. This scenario is based on the following facts - - No person resides in a single, fixed-receptor location for 24 h a day over a period of 70 years - - Risk values vary from one receptor to another, depending on source characteristics, meteorological conditions, and the distance downwind from the source - - No person spends his/her entire life outdoors. A person's exposure to outdoor air pollution sources, such as the M W C facility, is higher than indoors because structures and homes provide some shelter and reduce the ambient outdoor concentrations In general, the average residency in the same place for a family in the USA ranges from 10 to 20 years, which is much lower than the lifetime assumption of 70 years. The risk figures provided in Tables 5 and 6 are 1/10.5 (9.52%) of those listed in Tables 3 and 4. This implies that the highest individual excess carcinogenic risk in Table 5 is about 1/250 (0.4%) of the generally acceptable EPA carcinogenic risk for inhalation. Similarly, the highest individual noncarcinogenic risk given in Table 6 is about 1/2380 (0.04%) of the generally acceptable risk value. -
-
REFERENCES I 2 3 4
5
USEPA Municipal Waste Combustion Study, Emission data base for municipal waste combustors, EPA/530-SW-87-021b, June 1987. Code of Federal Regulations Part 51.118 Stack height provisions, 1988. USEPA Municipal Waste Combustion Study, Assessment of health risks associated with municipal waste combustion emissions, EPA/530-SW-87-021g, June 1987. USEPA, Office of Emergency and Remedial Response, Office solid waste and emergency response, Superfund Exposure Assessment Manual, OSWER Directive 9285.5-1, September 22, 1987. Radian Corporation, Locating and estimating air emissions from municipal waste combustors, Draft Report, EPA Contract Number 68-02-4392, October 24, 1988.
87
Air emissions from municipal waste combustion and their environmental effects A. Roffman and H.K. Roffman A WD Technologies Inc., Penn Center West, Bldg III, Suite 300, Pittsburgh, PA 15276, USA
ABSTRACT This paper addresses risk-assessment estimates associated with air emissions from MWC facilities via the inhalation pathway. Calculations performed address selected chemical constituents with the potential highest human health effects. The calculated carcinogenic risks are small and are well below the EPA acceptable risk of 10-4. Similarly, the calculated noncarcinogenic risks are well below the acceptable reference dose values. Calculations presented in this paper for selected constituents could be expanded to additional chemical constituents. INTRODUCTION Forecasts related to municipal solid waste (MSW) indicate an expected steady increase in volume, coupled with a corresponding decrease in the capacity of approved landfills. This issue has surfaced in many presentations and articles, with the prime concern being how to best deal with the situation. One o f the attractive alternatives for reducing the volume of M S W is burning it in municipal waste combustion ( M W C ) facilities. This approach has been adopted by many municipalities and local communities. It is anticipated that the number of M W C facilities in the USA, which now exceeds 100, m a y reach a b o u t 300 by the turn of the century. The increase in the number o f M W C facilities has increased the public concern a b o u t the potential environmental effects o f such facilities resulting from air emissions, discharges to water bodies, and the disposal o f generated ashes on land. This paper presents an analysis of the effects of air emissions from M W C facilities on the public health via inhalation. The analysis was performed for selected metals and organic constituents. The effects are expressed as excess cancer risks for carcinogenic constituents and as noncarcinogenic risks for noncarcinogenic constituents. The calculations provided in this paper are based on emission data presented in the U.S. Environmental Protection Agency (EPA) Municipal Waste C o m b u s t i o n Study [1], which is based on data compiled from existing facilities. Stack heights used in the calculations are 200-300
0048-9697/91/$03.50
© 1991 - - Elsevier Science Publishers B.V.
88
A. ROFFMAN AND H.K. ROFFMAN
feet*. These heights represent stack heights for new facilities and are in line with the Good Engineering Practices (GEP) stack-height regulations promulgated by the EPA [2]. Results of the calculations conducted for the selected constituents indicate that The estimated carcinogenic and noncarcinogenic risks resulting from air emissions from MWC facilities via the inhalation pathway are several orders of magnitude below the results presented in the EPA Municipal Waste Combustion Study [1]. - - The estimated carcinogenic risks are several orders of magnitude below the EPA generally accepted health risk level of 10 - 4 . The major differences between the calculations performed in this paper and those performed in the EPA study are rooted in several overconservative assumptions included in the EPA study. For example, the EPA report unrealistically assumes low stack heights for proposed new facilities. Such low stack heights would not pass the scrutiny of the EPA GEP regulations. Additional conservatism embedded in the EPA calculations is attributed to the emission rates for the constituents involved especially since the calculations are for proposed new facilities. Risk-assessment calculations were performed for selected constituents, including arsenic, cadmium, lead, and 2,3,7,8-tetrachlorodibenzodioxin (2,3,7,8-TCDD). These calculations can be expanded to include additional constituents by merely performing the appropriate scaling calculations. -
-
METHODOLOGY
A key input to the risk-assessment calculations is the calculated air concentrations of the selected constituents that are derived by one of the EPA air-quality guidelines dispersion models. Input data that drive the dispersion model include emission rates and stack parameters, meteorology, and a receptor grid representing the locations for which calculations are performed. Air-emission rates used in these dispersion calculations were derived from emission information provided in the EPA Municipal Combustion Study [1]. This reference report provides lowest and highest reported emission levels for mass burn, modular, and refuse-derived fuel (RDF) facilities. Table 1 provides the lowest and highest emission concentrations for arsenic, cadmium, lead, and 2,3,7,8-TCDD for the three types of MWC facilities. The emission concentrations were converted to emission rates, using data provided in ref. 1, and summarized in Table 2. The data presented in Table 2 are used in the dispersion calculations. *1
foot =
0.305m.
Munich Nalmo Marion County Wurzburg WSH/DI/FF
SD/FF
CYC/DI/ESP/FF
ESP/SD
0.018
452 6220 2.51 ×
l0 4
Hampton
Hampton Hampton Braintree
Facility name
Concentration (ngNm 3)
Facility name
Air pollution control
Highest emission
Lowest emission
ESP
ESP ESP ESP
Air pollution control
62.5
2.33 × 105 5.0 x 105 1.54 × 10 7
Concentration (ngNm -3)
Red Wing
2.3,7,8-TCDD
ESP
ESP
ESP
No pollution control ×
10 4
0.278
2.37 × 105
2.09
6090
Prince Edward Island Prince Edward Island Dyersburg
Tuscaloosa
No pollution control
No pollution control
No pollution control
ESP
1.54
1.55 x 107
9.42 × 105
1.19 × 10 -5
Albany Albany Albany Albany
ESP ESP ESP ESP
1.91 × 10 4 3.37 × l 0 4 9.73 x 10s 0.522
Akron Akron Akron Akron
ESP ESP ESP ESP
1.6 x 105 3.73 x 105 9.6 x 106 14.6
From US EPA Municipal Waste Combustion Study, EPA/530-SW-87-021b, June 1987. Nm -3, m 3 at normal conditions of 1 atmosphere and 20°C; ESP, electrostatic precipitator; SD, spray dryer; CYC, cyclone; DI, dry injection; FF, fabric filter; WSH, water spray humidifier.
Arsenic Cadmium Lead 2,3,7,8-TCDD
Municipal waste combustor facilities metals and organic constituents emission concentrations used in the calculationsa for refuse-derived fuel facilities
Barron County
Prince Edward Island Barron County
Lead
Cadmium
Arsenic
Municipal waste combustor facilities metals and organic constituents emission concentrations used in the calculationsa for modular facilities
2,3,7,8-TCDD
Arsenic Cadmium Lead
Constituent
Municipal waste combustor facilities metals and organic constituents emission concentrations used in the calculationsa for mass burn facilities
TABLE 1
OO
90
A. R O F F M A N A N D H.K. R O F F M A N
TABLE 2 Constituent emission rates used in calculationsa Constituent
Arsenic Cadmium Lead 2,3,7,8TCDD
Emission rate (mg h - I ) Mass burn facilities
Modular facilities
R D F facilities
5.8
6.2 x 101-9.07 x l03 1.55 x 102-9.55 x 103 1.81 x 103-1.22 x 105 0.02~).02
2,51 x 103-1.33 x 104 4.43 x 103-3.11 × 104 1.28 x 105-8.0 x 105 0.07- 1.22
x 101-5.06 x 103 2.8-1.09 x 104 1.57 x 103-5.47 x 105 0.0009- 1.36
aBased on measured data reported in the US EPA, Municipal Waste Combustion Study, EPA/530-SW-87-021b, June 1987.
It should be noted that the emission rates presented in Table 2 are based on measurements at existing facilities equipped with various types of airpollution control devices. These emissions do not necessarily represent stateof-the-art air-pollution control for new M W C facilities. This implies that the emission rates in Table 2 could represent conservative upper-limit emissions. Stack parameters, including stack exit diameters, exit temperatures, and exit velocities, were obtained from refs. 1 and 3. Stack heights used in the calculations were for facililites with 200- and 300-foot stacks. These heights were selected based on information obtained from owners of MWC facilities and represent present design for new facilities. The selected heights are higher than those used in the EPA Municipal Waste Combustion Study [3,5]. Meteorological data employed in the dispersion calculations included a STAR (STability ARay) tabulation of meteorological data consisting of the annual frequency distribution of wind speed and direction by atmospheric stability classes for a selected meteorological weather station. Key features of the meteorological data base are - - Predominant wind direction sectors are west-northwest, northwest, northnorthwest, and north (41.3 % of the time) and south-southwest and southwest (19.9% of the time) Atmospheric stability conditions determined by the use of sigma theta classifications indicate about 41% of neutral atmospheric conditions and 23% of stable atmospheric conditions. The industrial source complex (ISC) air dispersion model was used for performing annual dispersion calculations using the rural mode option. This is an EPA air-quality guideline dispersion model. Air concentrations were calculated at receptors located along the 16 cardinal wind directions on 10 concentric rings at distances of 0.5, 1.0, 1.5, 2.0, 3.0, 5.0, 7.5, 10.0, 12.5, and -
-
AIR EMISSIONS FROM MUNICIPAL WASTE COMBUSTION
91
15.0 km from the source. Maximum annual air concentrations served as input into the risk-assessment calculations. The risk-assessment methodology was based on the methodology outlined in the USEPA Superfund Assessment Manual [4] for the inhalation air pathway. The lifetime inhalation carcinogenic risk was calculated from the expression Individual excess cancer risk -- (concentration × daily inhalation rate x CPF x absorption fraction)/weight where concentration is the calculated maximum annual concentration of a constituent derived by the ISC dispersion model (/zgm-3); daily inhalation rate = 20 m 3 day-i for an adult; C P F is the carcinogenic potency factor (mg kg-I day-I), with values of 50 for arsenic, 6.1 for cadmium, and 1.56 × 105 for 2,3,7,8-TCDD; absorption fraction is the fraction of inhaled constituent that is absorbed through the lungs, assumed to be 0.5 for arsenic and cadmium and 0.55 for 2,3,7,8-TCDD; and weight is the individual's weight, assumed to be 70 kg for an adult. Lifetime risk means 24-h exposure per day over a period of 70 years. The inhalation noncarcinogenic risk was calculated from the expression. Individual noncarcinogenic risk -- (concentration × daily inhalation rate x "absorption fraction)/weight/reference dose where reference dose is the inhalation acceptable dose (mg kg-i day-l), with a value of 4.3 × l0 -4 for lead. In general, if the value of the individual noncarcinogenic risk is _< 1 it is considered an acceptable inhalation dose. RESULTS Dispersion calculations and associated risk-assessment calculations were performed using the emission rates provided in Table 2, for the four constituents of interest, the three types of MWC facilities, and two stack heights. A total of 48 computer runs were performed as part of those risk-assessment calculations. Tables 3 and 4, respectively, provide a summary of the estimated carcinogenic and noncarcinogenic risk resulting from air emissions from MWC facilities via the inhalation air pathway. The data in these tables represent maximum risk based on maximum annual calculated concentrations and lifetime exposure of 24 h per day over a lifetime of 70 years. This implies that the data in Tables 3 and 4 represent worst-case exposure scenarios. The maximum exposure risk for the 200-foot stack height occurs at a distance ranging from 500 to 1500 m from the stack, whereas the maximum exposure risk for the 300-foot stack occurs at a distance ranging from 1000 to 2000 m from the stack.
Arsenic Cadmium 2,3,7,8-TCDD
RDF
10 -9
1.8 x 10 -7 3.9 x 10 -7 1.7 x 10 -8
2.2 x 10 -8 6.1 x 10 8 2.6 x 10 -8
X
1.2 × 10 -6 3.4 x 10 -6 3.8 x 10 -7
9.3 × 1 0 - 7 4.1 x 10 6 1.9 x 10 -8
1.0 × 1 0 - 6 2.7 x 10 -6 9.5 x 10 -7
a W o r s t - c a s e e x p o s u r e is b a s e d o n 2 4 - h e x p o s u r e p e r d a y o v e r t h e a v e r a g e life o f 70 y e a r s . b U S E P A a c c e p t e d e x c e s s c a r c i n o g e n i c risk is 10 -4 ( o n e in t e n t h o u s a n d ) .
Arsenic Cadmium 2,3,7,8-TCDD
2.6 × 10 -9 4.4 × 10 - I °
Modular
4.8
Arsenic
Cadmium 2,3,7,8-TCDD
Mass burn
1.2 × 10 -7 2.5 x 10 -7 1.2 x 10 -8
1.1 x 10 -8 3.1 x 10 -8 1.2 x 10 -8
3.0 x 10 9 1.0 x 10 9 2.6 x 10 -10
Lowest reported e m i s s i o n level
Lowest reported e m i s s i o n level Highest reported e m i s s i o n level
300-foot stack height
200-foot stack height
I n d i v i d u a l e x c e s s c a r c i n o g e n i c risk ~
Constituent
Combustor type
7.7 x 10 -7 2.1 × 10 -6 2.3 x 10 -7
5.7 X 1 0 - 7 2.0 × 1 0 - 6 1.0 x 10 - s
5.4 x 10 7 1.5 × 10 -6 5.2 x 10 -7
Highest reported e m i s s i o n level
E s t i m a t e d c a r c i n o g e n i c risk r e s u l t i n g f r o m air e m i s s i o n s f r o m m u n i c i p a l w a s t e c o m b u s t o r s - - i n h a l a t i o n air p a t h w a y , w o r s t - c a s e e x p o s u r e a
TABLE 3
Z
O
Z
'7
tO
Lead Lead Lead
Mass b u r n Modular RDF
1.1 x 10 5 2.7 x 10 -5 4.3 x 10 4
Lowest r e p o r t e d emission level
200-foot stack height
4.4 x 10 3 2.2 x 10 3 3.3 x 10 .3
Highest r e p o r t e d emission level
Individual n o n c a r c i n o g e n i c risk
6.0 x 10 6 1.4 x 10 -5 2.7 x 10 4
Lowest r e p o r t e d emission level
300-foot stack height
2.5 x 10 3 1.0 x 10 3 2.1 × 10 .3
Highest reported emission level
i n h a l a t i o n air pathway, worst-case exposure"
a Worst-case exposure is based on 24-h exposure per day over the average life o f 70 years. A n o n c a r c i n o g e n i c risk is m e a s u r e d as a ratio between the calculated dose and the reference dose. A q u a n t i t y _< 1 is considered a n o n c a r c i n o g e n i c acceptable risk.
Constituent
Combustor type
Estimated n o n c a r c i n o g e n i c risk resulting from air emissions from municipal waste c o m b u s t o r s
TABLE 4
Arsenic Cadmium 2,3,7,8-TCDD
Arsenic Cadmium 2,3,7,8-TCDD
Arsenic Cadmium 2,3,7,8-TCDD
Mass burn
Modular
RDF
1.7 x 10 8 3.7 × 10 -8 1.6 × 1 0 - 9
2.1 x 10 -9 5.8 × 10 -9 2.5 × 1 0 - 9
4 . 6 x 10 - l ° 2.5 x 10 -1° 4.1 x 10 - t l
1.1 x 10 -7 3.2 × 10 7 3.6 x 10 8
9.3 × 10 8 3.9 × 10 -7 1.8 × 1 0 - 9
9.8 x 10 - s 2.6 X 1 0 - 7 9.0 x 10 -8
1.1 x 10 8 2.4 × 10 -8 1.1 × 1 0 - 9
1.0 × 10 -9 2.9 × 10 -9 1.2 × 10 -8
2.9 x 10 - l ° 9.7 x 10 -1' 2.4 x 10 - l l
Lowest reported e m i s s i o n level
Lowest reported e m i s s i o n level Highest reported e m i s s i o n level
300-foot stack height
200-foot stack height
I n d i v i d u a l e x c e s s c a r c i n o g e n i c risk b
a Realistic c a s e e x p o s u r e is b a s e d o n 8 - h e x p o s u r e p e r d a y o v e r a p e r i o d o f 20 y e a r s . b U S E P A a c c e p t e d e x c e s s c a r c i n o g e n i c risk is 10 -4 ( o n e in t e n t h o u s a n d ) .
Constituent
Combustor type
7.1 x 10 -8 2.0 × 10 -7 2.2 x 10 8
5.7 × 10 8 1.9 × 10 -7 9.0 x 10 -~°
5.3 x 10 8 1.4 × 1 0 - 7 4.9 x 10 -8
Highest reported e m i s s i o n level
E s t i m a t e d c a r c i n o g e n i c risk r e s u l t i n g f r o m air e m i s s i o n s f r o m m u n i c i p a l w a s t e c o m b u s t o r s - - i n h a l a t i o n air p a t h w a y , realistic c a s e e x p o s u r e a
TABLE 5
Lead Lead Lead
Mass b u r n Modular RDF
1.1 × 10 -6 2.6 × 10 6 4.1 × 10 -5
Lowest reported emission level
200-foot stack height
4.2 × 10 -4 2.1 × 1 0 - 4 3.2 × 10 -4
Highest r e p o r t e d emission level
Individual n o n c a r c i n o g e n i c risk a
6.0 × 10 7 1.3 × 10 6 2.6 × 10 5
Lowest r e p o r t e d emission level
300-foot stack height
2.4 × 10 4 1.0 × 10 4 2.0 × 10 4
Highest reported emission level
Realistic case exposure is based o n 8-h exposure per day over a period o f 20 years. A n o n c a r c i n o g e n i c risk is m e a s u r e d as a ratio between the calculated dose a n d the reference dose. A q u a n t i t y < 1 is considered a n o n c a r c i n o g e n i c acceptable risk.
Constituent
Combustor type
Estimated n o n c a r c i n o g e n i c risk resulting from air emissions f r o m municipal waste c o m b u s t o r s - - i n h a l a t i o n air p a t h w a y , realistic case exposure a
TABLE 6
96
A. ROFFMAN AND H.K. ROFFMAN
The USEPA acceptable individual excess carcinogenic risk for inhalation is 10 -4, o r one in 10 000 persons. The highest risk listed in Table 3 is 4.1 × 10 -6,
which is about 1/24, or 4.2% of the EPA acceptable carcinogenic risk for inhalation. Similarly, the noncarcinogenic risk figures provided in Table 4 indicate that the highest risk is 4.4 x 10 -3, about 1/227, or 0.4% of the acceptable value. Tables 5 and 6, respectively, provide a summary of estimated carcinogenic and noncarcinogenic risks resulting from air emissions from M W C facilities via the inhalation air pathway for a more realistic case. In this case an "8 hour a day" exposure over only 20 years is assumed. This scenario is based on the following facts - - No person resides in a single, fixed-receptor location for 24 h a day over a period of 70 years - - Risk values vary from one receptor to another, depending on source characteristics, meteorological conditions, and the distance downwind from the source - - No person spends his/her entire life outdoors. A person's exposure to outdoor air pollution sources, such as the M W C facility, is higher than indoors because structures and homes provide some shelter and reduce the ambient outdoor concentrations In general, the average residency in the same place for a family in the USA ranges from 10 to 20 years, which is much lower than the lifetime assumption of 70 years. The risk figures provided in Tables 5 and 6 are 1/10.5 (9.52%) of those listed in Tables 3 and 4. This implies that the highest individual excess carcinogenic risk in Table 5 is about 1/250 (0.4%) of the generally acceptable EPA carcinogenic risk for inhalation. Similarly, the highest individual noncarcinogenic risk given in Table 6 is about 1/2380 (0.04%) of the generally acceptable risk value. -
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REFERENCES I 2 3 4
5
USEPA Municipal Waste Combustion Study, Emission data base for municipal waste combustors, EPA/530-SW-87-021b, June 1987. Code of Federal Regulations Part 51.118 Stack height provisions, 1988. USEPA Municipal Waste Combustion Study, Assessment of health risks associated with municipal waste combustion emissions, EPA/530-SW-87-021g, June 1987. USEPA, Office of Emergency and Remedial Response, Office solid waste and emergency response, Superfund Exposure Assessment Manual, OSWER Directive 9285.5-1, September 22, 1987. Radian Corporation, Locating and estimating air emissions from municipal waste combustors, Draft Report, EPA Contract Number 68-02-4392, October 24, 1988.
