Outdoor fine and ultrafine particle measurements at six bus stops with smoking on two California arterial highways—Results of a pilot study

Figures & data

Table 1. Locations and characteristics of 6 bus stops in the present study

Bus Stop	Location of Bus Stop	City ^a	Distance from Curb (m)	Traffic Volume ^b (vehicles/hr)	Temp. ^c (°C)	RH ^c (%)	Wind Speed ^c (m/sec)
A	Woodside Rd. near Kentfield Ln.	RC	2.1	3280, ^d 4620	19.4	55	0.74 (SD 0.54)
B	Woodside Rd. near Atherwood Ave.	RC	3.3	3312	21.1	43	1.26 (SD 1.20)
C	El Camino Real near Quarry Rd.	PA	2.7	3480	26.0	49	0.60 (SD 0.52)
D	El Camino Real near Center St.	RC	2.0	4416	20.9	53.8	1.13 (SD 0.60)
E	El Camino Real near Cambridge Ave.	MP	1.5	5100	—	—	—
F	El Camino Real near Encinal Ave.	MP	1.8	3740	17.9	54.7	0.44 (SD 0.37)
Notes:
^aNames of towns: RC = Redwood City; PA = Palo Alto; MP = Menlo Park.
^bEstimated from 7–11 1-min visual vehicle counts during each experiment (see text).
^cMeans of TSI VelociCalc-Plus measurements of weather data during each experiment.
^dNonstandard position for first cigarette: smoker second from end; a separate traffic volume was obtained. The standard position (smoker at end of bench) was used for the 12 remaining cigarettes.

Table 2. PM_2.5 personal exposure of one smoker and three nonsmokers sitting on bus stop benches during smoking period (μg/m³)

					Exposure of Nonsmokers
Cigarette No.	Bus Stop	Cigarette Time (min)	Background ^a	Smoker's Exposure ^b	0.5 m	1.0 m	1.5 m
1	A ^c	4:33	1.9	422	102 ^d	1.9	—
2	A	5:05	1.2	417	153	173	83
3	A	4:45	1.2	118	24	12	11
4	A	6:03	1.9	89	17	17	16
5	B	4:30	1.9	138	51	29	13
6	B	4:57	1.6	42	15	5	3
7	C	3:55	2.5	76	46	24	28
8	C	4:15	1.3	211	59	28	32
9	D ^e	5:16	1.3	26	70	44	24
10	D ^e	5:00	1.5	88	138	49	33
11	E	3:45	1.7	192	37	39	21
12	E	3:29	1.7	424	96	78	48
13	F	4:40	2.7	283	59	16	—
Mean	—	4:38	1.7	192.0	59.0	40.0	28.0
SD	—	0:41	0.5	145.7	46.0	45.0	22.1
Notes:
^aMean of background before cigarette 1, between cigarettes, and after cigarette 2.
^bMean of 1-sec readings in the smoker's breathing zone during smoking.
^cNonstandard position: Smoker was second from end.
^dMeasurements on either side of the smoker (1.8 and 202 μg/m^3) were averaged.
^ePositions reversed with respect to direction of traffic.

Figure 1.Scale drawing showing positions of four to five persons at bus stops along the two California arterial highways.

Figure 2.Time series of breathing-zone PM_2.5 exposures of one smoker and three nonsmokers measured during the 1-hr visit to Bus Stop E on El Camino Real and Cambridge Avenue.

Figure 3.Frequency distributions of PM_2.5 breathing-zone exposures of four persons sitting on the bench at Bus Stop E along with a standing person showing the first cigarette (top) and second cigarette (bottom).

Table 3. Ninety-fifth percentile PM_2.5 exposures in μg/m³ for 13 cigarettes smoked at six bus stops

			Nonsmokers Sitting on Bench
Cigarette No.	Bus Stop	Smoker	0.5 m	1.0 m	1.5 m	Nonsmoker Standing	Background (95th percentile)
1	A	2032	1064	3.5	—	—	4.0 ^a
2	A	2737	697	953.	428	—	3.2 ^b
3	A	510	112	68	47	—	2.0 ^a
4	A	470	83	74	12	—	2.8 ^b
5	B	868	204	87	46	—	4.8 ^a
6	B	198	74	19	9	—	0.9 ^b
7	C	340	98	181	84	—	3.8 ^a
8	C	1038	117	244	101	—	4.0 ^b
9	D	53	252	156	115	16.2	2.8 ^a
10	D	445	640	194	112	56.4	3.4 ^b
11	E	1032	157	170	157	16.1	3.4 ^a
12	E	1905	343	283	192	3.8	3.5 ^b
13	F	1885	302	55	—	79.5 ^c , 23.7 ^d	4.0 ^a , 4.9 ^b
Notes:
^aBackground before smoking.
^bBackground after smoking.
^cStanding person in normal position.
^dStanding person at end of bench from smoker.

Figure 4.Frequency distributions of PM_2.5 breathing-zone exposures of four persons on the bench at Bus Stop B for the first cigarette (top) and second cigarette (bottom) showing the relative straightness of distributions after adjustment by subtracting a small shift parameter from all exposures (1.3 μg/m³).

Table 4. Adjusted PM_2.5 exposures for two smoking periods at Bus Stop B, with arithmetic and geometric parameters of lognormal model estimated by linear regression

		Arithmetic Statistics ^a ^, ^b		Geometric Parameters ^b
Monitor ID	Location	Mean (μg/m^3)	SD (μg/m^3)	μg (μg/m^3)	σg	R ^2 (%)
Cigarette 1
SP-4	Smoker	136	539	1.52	36.8	98.9
SP-16	Sitting first left of smoker	50	264	1.00	24.0	99.3
SP-8	Sitting second left of smoker	28	153	0.70	17.0	98.2
SP-6	Sitting third left of smoker	12	64	2.17	13.5	97.6
SP-4	Background before cigarette 1	1.3	1.7	0.15	7.0	97.2
Cigarette 2
SP-4	Smoker	41	169	0.64	19.8	99.0
SP-16	Sitting first left of smoker	14	36	1.28	17.7	96.8
SP-8	Sitting second left of smoker	4	0.7	0.43	10.8	98.0
SP-6	Sitting third left of smoker	1.6	4.3	0.41	6.0	97.7
SP-4	Background between cigs	1.8	1.6	0.12	8.1	96.7
SP-4	Background after cigarette 2	2.4	5.5	0.12	6.9	97.0
Notes:
^aStatistics of 1-sec measurements; increment of 1.3 μg/m^3 subtracted. SD = arithmetic standard deviation of model.
^bParameters of lognormal model fit by linear regression.

Table 5. Ultrafine particle (UFP) concentrations measured by the person sitting next to the smoker for 13 cigarettes during seven bus stop smoking experiments ^a

Bus Stop	Before First Cigarette	During First Cigarette	Between Both Cigarettes	During Second Cigarette	After All Cigarettes
A1	9600	8300	11,200	35,000	10,500
A2	2300	56,000	5400	96,600	10,500
B	2500	13,600	6500	24,000	5400
C	7500	21,400	4200	20,200	2900
D	5100	31,100	2200	55,500	2200
E	9000	120,000	15,200	99,300	9900
F	11,500	14,900	9800	—	—
Mean	6800	33,900	7800	55,100	6900
SD	3600	41,700	4500	35,400	3900
Note: ^aRaw data: Background levels not subtracted.

Figure 5.Time series of ultrafine particle concentration (top) and PM_2.5 exposure (bottom) for the person sitting closest (0.5 m) to the smoker during the 1-hr visit to Bus Stop E.

Figure 6.Time series of ultrafine particle concentration (top) and PM_2.5 exposure (bottom) for the person sitting closest (0.5 m) to the smoker during the half-hour visit to Bus Stop F.