. 2007 Jul 5;115(10):1388–1393. doi: 10.1289/ehp.10043

Table 2.

Basis and data source for classifying air pollutants in “probable risks” category in Greater Houston.^a

			Data source
			AQS 2004^b		NATA 1999^c
	Basis		No. of monitors		No. of census tracts
Air pollutant	Cancer risk	Chronic risk	Cancer risk	Chronic risk	Cancer risk	Chronic risk
Vinyl chloride	X				1
Acrylic acid		X				1
Acetaldehyde	X	X	2	1	48	1
Ethylene dichloride(1,2-dichloroethane)	X		1		5
Naphthalene	X				10
Arsenic compounds(inorganic may include arsine)	X				7
Carbon tetrachloride	X		16		895
Ethylene oxide	X				9
1,1,2,2-Tetrachloroethane	X		2

Abbreviations: AQS, Air Quality System; X denotes the basis for risk classification.

Greater Houston consists of the 10-county, Houston–Sugar Land–Baytown metropolitan statistical area defined by the U.S. Census Bureau (2003).