Table 2

Air pollution average concentration of the sampled areas

Area	Distance from roadway	NO₂ concentration (ppb)*				SPM concentration (μg/m³)†				Group
Area	Distance from roadway	n	Mean	SD	Range	n	Mean	SD	Range	Group
*The average concentration of the five-year period (1990–94) measured at ambient air monitoring.
†The average concentration of the eight-year period (1987–94) measured at ambient air monitoring.
SD, standard deviation.
Chuo ward	0 m	51	51.6	7.8	33–65	87	47.6	16.8	19.2–99.8	1
	20 m	32	44.0	9.0	27–64	87	43.3	18.0	16.3–95.8	2
Ohta ward	0 m	51	52.0	12.1	27–83	87	51.6	18.6	12.1–102.3	1
	20 m	51	45.7	10.3	25–75	87	46.4	16.8	21.1–100.8	2
Shibuya ward	0 m	51	56.1	10.1	33–77	87	61.8	21.7	30.2–131.0	1
	20 m	51	42.6	10.2	24–75	85	38.8	15.7	10.6–94.8	2
Itabashi ward	0 m	51	53.6	12.0	30–80	87	59.2	23.0	22.5–140.6	1
	20 m	32	44.0	10.6	24–67	87	45.7	19.8	9.9–112.2	2
Tanashi City	0 m	47	47.2	9.7	29–65	85	56.8	23.9	11.1–135.5	1
	20 m	26	37.8	9.2	23–54	83	46.0	22.3	7.3–108.2	2
Hachioji City	0 m	51	38.7	8.2	24–57	85	44.3	15.5	16.8–82.2	2
	20 m	32	32.8	6.6	21–43	87	39.4	13.7	10.5–82.5	3
Tachikawa City	0 m	50	41.8	9.8	24–59	75	45.1	17.4	15.4–88.6	2
	20 m	32	33.9	8.2	19–46	75	38.9	14.4	11.0–77.1	3
Machida City	0 m	51	40.1	9.0	23–56	87	43.1	17.9	11.1–108.1	2
	20 m	31	35.6	8.2	22–51	82	33.9	15.8	5.0–74.7	3
Ome City	0 m	51	29.0	6.0	18–49	87	34.5	14.7	7.3–89.2	3
	20 m	32	23.5	5.4	14–33	87	28.1	13.8	3.4–69.7	3