Table 17.

Comparison of BTEX Ratios from Other Studies

Ratios	U.S. Roadwaysa	U.K. Roadwaysb	U.K. Cars and Buses (In-Vehicle)b	Spanish Public Buses (In-Vehicle)c	U.K. Bus Stationb
Toluene:Benzene	[~1.6–1.9]	2.2	2.4–3.4	[~3.4–2.5]	2.4
Toluene:Xylene	[~0.9]	1.9	1.9–2.1	[~0.5]	2.8
Toluene:Ethylbenzene	3.6–5.6	8.7	8.7–9.5	5.7–6.3	12.4
Benzene:Xylene	[~0.5]	0.9	0.6–0.9	[~0.6]	1.2
Benzene:Ethylbenzene	2.3–2.9	4.0	2.5–3.9	1.7–2.5	5.3
Xylene:Ethylbenzene	4.3–6.0	4.6	4.5–4.6	2.6–3.1	4.5

Note: Values in brackets were calculated from other ratio values in the Table, such as Toluene:Benzene = Toluene:Ethylbenzene divided by Benzene:Ethylbenzene. These are only approximate because contributors to the ratios may not be the same in the numerator and denominator.

^aMuhamed et al. 2002.

^bKim et al. 2001.

^cParra et al. 2008.