June 2009
Front Matter
Training
49
Appendix
Residence Times
17 hrs
Acrolein
27 hrs
Vinyl Chloride
26 hrs
Formaldehyde
2.8 hrs
1,3-Butadiene
12 hrs
Acetaldehyde
16 hrs
Naphthalene
N/A**
Arsenic and other toxic metal compounds
2 days
Ethylbenzene
2.4 days
Acrylonitrile
84 hrs
Trichloroethylene
weeks*
1,2-Dichloropropane
84 hrs
Benzene
months
Methylene Chloride
months
Tetrachloroethylene
months
Chloroform
decades
Carbon Tetrachloride
Lifetime by reaction with OH
Species
*   Wet deposition is also a sink
** Lifetime is dependant on particle deposition and is typically days to weeks.  Deposition time is primarily determined by the size of the particles.
•Approximate atmospheric residence times for some air toxics are listed here. 
•These values were found at http://www.scorecard.org/chemical-profiles/. To find the atmospheric persistence of other air toxics, enter the pollutant’s name in the chemical profile.  Once the pollutant page is available, select “links” and the entry for “CalEPA Air Resources Board Toxic Air Contaminant Summary”.  A summary of physical properties is provided including atmospheric persistence.