Benzene releases from gasoline stations - Implications for human health: Appendix B

Exposure characterization for benzene evaporative release from gasoline stations

Table B-1. Inputs to SCREEN3 for benzene exposure in the vicinity of gasoline stations resulting from total evaporative loss
Variables	Input variables
Source type	Area
Effective emission area^{Footnote a}	20 m × 20 m
Effective emission height	2.3 m (average of vent [at 3.66 m] and gas pump [1 m] release heights)
Gasoline density (g/mL)	0.755
Benzene content in gasoline (% v/v)	0.6
Gasoline station throughput, median (baseline; high) (million L/year)	4.0 (1; 10.6)
Total gasoline evaporative loss (%)	0.15
Emission rate of benzene, median (baseline; high) (mg/s)	1.0 (0.25; 2.65)
Receptor height^{Footnote a}	1.74 m (average adult height)
Source release height^{Footnote b}	2.3 m
Adjustment factor^{Footnote c}	0.4 (variable wind direction during 24-hour period) 0.2 (average wind direction during 1-year period)
Urban–rural option	Urban
Meteorology^{Footnote d}	1 (full meteorology)
Minimum and maximum distance	10–1000 m
1 Curry et al. (1993) Return to footnote a referrer 2 Average of vent pipe and gas pump height Return to footnote b referrer 3 US EPA (1992) Return to footnote c referrer 4 Default value in SCREEN3 Return to footnote d referrer

Table B-2. Average annual concentrations of benzene in the vicinity of gasoline stations resulting from total evaporative emissions for baseline, median and high throughput gasoline stations
Distance (m)	Benzene concentration from baseline (1 million L/year) throughput gasoline stations (μg/m³)	Benzene concentration from median (4 million L/year) throughput gasoline stations (μg/m³)	Benzene concentration from high (10.6 million L/year) throughput gasoline stations (μg/m³)
10	0.783	3.01	7.97
20	0.885	3.47	9.21
25	0.714	2.86	7.57
30	0.616	2.45	6.48
40	0.493	1.96	5.20
50	0.404	1.61	4.27
60	0.331	1.32	3.50
70	0.273	1.09	2.89
80	0.227	0.91	2.41
90	0.191	0.76	2.03
100	0.163	0.65	1.72
105	0.150	0.60	1.60
110	0.140	0.56	1.48
120	0.121	0.48	1.29
130	0.106	0.42	1.13
140	0.094	0.37	0.99
150	0.083	0.33	0.88
160	0.075	0.30	0.79
170	0.067	0.27	0.71
175	0.064	0.26	0.68
180	0.061	0.24	0.65
185	0.058	0.23	0.62
190	0.055	0.22	0.59
200	0.051	0.20	0.54
210	0.047	0.19	0.49
220	0.043	0.17	0.45
230	0.040	0.16	0.42
240	0.037	0.15	0.39
250	0.034	0.14	0.36
260	0.032	0.13	0.34
270	0.030	0.12	0.32
280	0.028	0.11	0.30
290	0.026	0.11	0.28
300	0.025	0.10	0.26
400	0.015	0.06	0.16
500	0.010	0.04	0.11
600	0.008	0.03	0.08
700	0.006	0.02	0.06
800	0.005	0.02	0.05
900	0.004	0.02	0.04
1000	0.003	0.01	0.04

Table B-3. Inputs to SCREEN3 calculation of benzene emissions from gasoline tanks as a result of unloading from tanker trucks
Variables	Input variables
Source type	Area
Effective emission area^{Footnote a}	0.3 m × 3 m
Average (upper bound) volume of gasoline tanker truck	35,000 L (43,900 L)
Gasoline unloading time from truck	1 hr
Ratio of air to gasoline vapour in storage tank	70:30 (v/v %)
Density of air + gasoline vapour mixture	1.682 kg/m³
Percent benzene (wt%) in air + gasoline mixture in gasoline storage tank	0.18%
Release rate of benzene for average (upper bound) tanker truck	0.029 g/s (0.037 g/s)
Emission rate of benzene for average (upper bound) tanker truck	3.27×10^-5 g/(s·m²) (4.1×10^-5 g/(s·m²)
Receptor height	1.74 m (average adult height)
Source release height^{Footnote b}	3.66 m
Urban–rural option	Urban
Meteorology	1 (full meteorology)
Minimum and maximum distance	10–1000 m
1 Professional judgment based on evaluations of satellite images Return to footnote a referrer 2 CAPCOA (1997) Return to footnote b referrer

Table B-4. The maximum 1 hr air concentrations of benzene in the vicinity of a gasoline station for 35,000 and 43,900-L tanker truck unloading
Distance (m)	Maximum 1 hr conc. of benzene (μg/m³) for 35,000 L tanker truck	Maximum 1 hr conc. of benzene (μg/m³) for 43,900 L tanker truck
10	805.20	1009.95
20	647.40	812.02
30	477.66	599.12
40	360.84	452.60
50	280.08	351.30
60	221.04	277.25
70	177.36	222.46
80	144.72	181.52
90	119.94	150.44
100	100.86	126.51
120	74.10	92.94
140	56.69	71.11
150	50.23	63.01
160	44.83	56.23
180	36.40	45.66
200	30.19	37.87
210	27.69	34.73
220	25.63	30.72
230	23.56	29.55
240	21.84	27.39
250	20.32	25.49
270	17.74	22.25
300	14.73	18.48
400	8.93	11.20
500	6.10	7.65
600	4.50	5.64
700	3.49	4.38
800	2.82	3.53
900	2.34	2.93
1000	1.98	2.48

Table B-5. Inputs to AERSCREEN for benzene exposure in the vicinity of gasoline stations resulting from total evaporative loss
Variables	Input variables
Source type	Area
Effective emission area^{Footnote a}	20 m × 20 m
Gasoline density (g/mL)	0.755
Benzene content in gasoline (% v/v)	0.6
Gasoline station throughput, median (baseline; high) (million L/year)	4.0 (1;10.6)
Total gasoline evaporative loss (%)	0.15
Emission rate of benzene, median throughput station (mg/s)	1.0
Receptor height^{Footnote b}	1.74 m (average adult height)
Release height above the ground^{Footnote c}	2.3 m (average of vent [at 3.66 m] and gas pump [1 m] release heights)
Initial vertical dimension^{Footnote a}	3.3 m
Urban or rural	Urban
Population size of urban area^{Footnote d}	520 000
Average min/max temperature^{Footnote d} (ºK)	277/286
Source elevation^{Footnote a} (m)	0
Minimum wind speed^{Footnote e} (m/s)	0.5
Anemometer height^{Footnote e} (m)	10
Adjustment factor^{Footnote e}	0.6 (variable wind direction during 24-hour period) 0.1 (average wind direction during 1-year period)
Meteorology^{Footnote a}^{Footnote e}	AERMET seasonal tables dominant surface profile/urban/average moisture
Minimum and maximum distance	1–5000 m
1 Professional judgment based on evaluations of satellite images Return to footnote a referrer 2 Curry et al. (1993) Return to footnote b referrer 3 CAPCOA (1997) Return to footnote c referrer 4 Canada (2014) Return to footnote d referrer 5 Default value in AERSCREEN Return to footnote e referrer

Table B-6. Average annual concentrations of benzene in the vicinity of gasoline stations resulting from total evaporative emissions for median-throughput gasoline stations calculated using AERSCREEN
Distance (m)	Benzene concentration from median (4 million L/year) throughput gasoline stations (μg/m³)
1	1.4600
25	1.1000
50	0.4183
75	0.2370
100	0.1585
125	0.1160
150	0.0900
175	0.0726
200	0.0603
225	0.0513
250	0.0443
275	0.0388
300	0.0344
325	0.0308
350	0.0279
375	0.0253
400	0.0232
425	0.0213
450	0.0197
475	0.0183
500	0.0170
525	0.0159
550	0.0149
575	0.0140
600	0.0132
625	0.0125
650	0.0119
675	0.0113
700	0.0107
725	0.0102
750	0.0097
775	0.0093
800	0.0089
825	0.0085
850	0.0082
875	0.0079
900	0.0076
925	0.0073
950	0.0070
975	0.0068
1000	0.0066

Table B-7. Inputs to AERSCREEN calculation of benzene emissions from gasoline tanks as a result of unloading from a tanker truck
Variables	Input variables
Source type	Area
Effective emission area^{Footnote a}	0.3 m × 3 m
Average volume of gasoline tanker truck	35,000 L
Ratio of air to gasoline vapour in storage tank	70:30 (v/v %)
Density of air + gasoline vapour mixture	1.682 kg/m³
Percent benzene (wt%) in air+gasoline mixture in gasoline storage tank	0.18%
Release rate of benzene for average tanker truck	0.029 g/s
Receptor height^{Footnote b}	1.74 m (average adult height)
Source release height^{Footnote c}	3.66 m
Initial vertical dimension^{Footnote a}	4.66 m
Urban or rural	Urban
Population size of urban area^{Footnote d}	520 000
Average min/max temperature^{Footnote d} (ºK)	277 / 286
Source elevation^{Footnote a} (m)	4.3
Minimum wind speed^{Footnote e} (m/s)	0.5
Anemometer height^{Footnote e} (m)	10
Source release height^{Footnote a}^{Footnote c}	2.3 m
Meteorology^{Footnote a}^{Footnote d}	AERMET seasonal tables dominant surface profile/urban/average moisture
Minimum and maximum distance	1–5000 m
1 Professional judgment based on evaluations of satellite images Return to footnote a referrer 2 Curry et al. (1993) Return to footnote b referrer 3 CAPCOA (1997) Return to footnote c referrer 4 Canada (2014) Return to footnote d referrer 5 Default value in AERSCREEN Return to footnote e referrer

Table B-8. The maximum 1 hr air concentrations of benzene in the vicinity of a gasoline station for 35,000 L tanker truck unloading calculated using AERSCREEN
Distance (m)	Maximum 1 hr conc. of benzene (μg/m³) for 35,000 L tanker truck
1	1722.0000
25	259.7000
50	104.4000
75	59.7100
100	40.0300
125	29.3400
150	22.7700
175	18.3800
200	15.2700
225	12.9600
250	11.2000
275	9.8180
300	8.7040
325	7.7920
350	7.0340
375	6.3940
400	5.8490
425	5.3800
450	4.9720
475	4.6150
500	4.3000
525	4.0210
550	3.7710
575	3.5470
600	3.3460
625	3.1630
650	2.9970
675	2.8450
700	2.7060
725	2.5790
750	2.4610
775	2.3530
800	2.2530
825	2.1590
850	2.0730
875	1.9920
900	1.9160
925	1.8450
950	1.7790
975	1.7170
1000	1.6580