Table I.

Airborne Contaminants Used in Formulating the Inhalation Exposure Index for Premature Birth (PB) and Low Birth Weight (LBW) Risks Along with the (Noncancer) Toxicity Reference Concentrations (from USEPA⁽⁷⁾)

Chemical Name of Air Pollutant	CAS Number	Reference Concentrations (RfCs)(mg/m3 Unless Indicated Otherwise)
Criteria pollutants
Ozone (O3)	10028-15-6	30 ppm (summer season average)
Nitrogen dioxide (NO2)	10102-44-0	0.015
Sulfur dioxide (SO2)	94336-28-4	53 ppb
Fine particulate matter (PM2.5)	NA	30 ppb
Air toxics
Acetaldehyde	75070	0.009
Acrolein	107028	0.00002
Acrylic acid	79107	0.001
Acrylonitrile	107131	0.002
Antimony compounds	7440360	0.0002
Beryllium compounds	7440417	0.00002
Bis(2-ethylhexyl)phthalate	117817	0.01
Chlorine	7782505	0.00015
2-Chloroacetophenone	532274	0.00003
Chloroprene	126998	0.007
Chromium compounds	18540299	0.0001
Cobalt compounds	7440484	0.0001
1,3-Dichloropropene	542756	0.02
Diesel particulate matter	N/A	5
Diethanolamine	111422	0.003
Epichlorohydrin	106898	0.001
1,2-Epoxybutane	106887	0.02
Ethylene dibromide (Dibromomethane)	106934	0.009
Ethylene glycol	107211	0.4
Formaldehyde	50000	0.0098
Hexachlorocyclopentadiene	77474	0.0002
Hexamethylene-1,6-diisocyanate	822060	0.00001
Hydrochloric acid	7647010	0.02
Maleic anhydride	108316	0.0007
Methyl bromide (bromomethane)	74839	0.005
Methyl isocyanate	624839	0.001
Methyl methacrylate	80626	0.7
4,4′-Methylene diphenyl diisocyanate (MDI)	101688	0.0006
Naphthalene	91203	0.003
Nickel compounds	7440020	0.00009
Nitrobenzene	98953	0.009
Phosgene	75445	0.0003
Phthalic anhydride	85449	0.02
Propionaldehyde	123386	0.008
Propylene dichloride	78875	0.004
Propylene oxide	75569	0.03
Styrene oxide	96093	0.02
Titanium tetrachloride	7550450	0.0001
Toluene	108883	5
2,4-Toluene diisocyanate	584849	0.00007
Triethylamine	121448	0.007
Vinyl acetate	108054	0.2