September 15, 2008

Updates since 7/12/07 are that the NEI 2002v2.1 at the Tier 1 level were updated with the NEI
2005 v1 at the Tier 1 level.  The values for 2003 and 2004 were calculated using an interpolation
between 2002 and 2005.  For 2006 and 2007 the values were interpolated between NEI 2005v1 and the 2009
model predicted inventory.

July 12, 2007

Updates since 8/5/05 are that the 2002 Preliminary values were replaced with the 2002 
v2.1 NEI at the TIER 1 level.  The values for 2003 to 2006 were interpolated between the 
2015 model predicted inventory and the 2002 v2.1 NEI.  For questions about the trends
data, please contact Rhonda Thompson at thompson.rhonda@epa.gov.

August 8, 2005

The name, Air Pollutant Emissions Trends Data, was changed to the National Emissions 
Inventory (NEI) Air Pollutant Emissions Trends Data.  The addition of 'National 
Emissions Inventory' was done to reflect the source of the trends data.  The raw NEI data 
can be found here:  http://www.epa.gov/ttn/chief/net/index.html

READ ME file for the National Emissions Inventory (NEI) Trends Report dated 
07/18/05.  This includes all changes to the Trends Report since September, 2004.

Between September 2004 and the 11/15/04 posting of the NEI Trends Report the 
following changes were made to the detail data.

A new methodology was developed to estimate emissions from woodstoves.  This new 
methodology is reflected in the 1999 Emissions only.  (Tier 3 in the Trends Report will 
be affected for VOC, PM10, and PM25).  Subsequent versions of the NEI will include the 
application of this new method for all years later than 1999.

To be consistent with the 2001 inventory used in the Clean Air Interstate Rule (CAIR), 
Tier 7 was updated for Commercial Cooking and Tier 13 was updated for paved and 
unpaved road dust for 2001 only.  Tier 7 updates affected CO, NOx, VOC, PM10 and 
PM25.  Tier 13 updates affected VOC, PM10 and PM25. 

For CO in 2001 a new methodology was used for open burning affecting Tier 10.  The 
September version of the NEI Trends Report included a draft number of 1852 (thousand 
short tons) in Tier 10 for 2002 CO.  The 11/15/04 posting of the NEI Trends Report 
includes the final estimate of 1847 (thousand short tons).


Between 11/15/04 and 1/05/05 some SCCs were reassigned from Miscellaneous Tier 3 
categories the appropriate categories which held Not Applicable (NA) where the value 
was supposed to be.  This occurred in CO, NOX, VOC Highway Diesels for 1990, 1996, 
and 1999-2002 and in NH3 Agriculture for 2002 and the PMs Railroads for 1990 and 
1996-1998.  Only the tier 3 numbers changed, no tier2 or 1 totals changed.


Between 1/05/05 and 3/23/05 some SCCs were reassigned in Tier 2 and Tier 3 categories 
under the Highway Vehicles (Tier1 – 11) category.  Most notably, some Gas SCCs (Tier2 
– 1-3) had been erroneously assigned to Diesels (Tier2 – 4).  This occurred for CO, NOX, 
and VOC.  Only the tier 2 and 3 numbers changed, under the Highway Vehicles (Tier1 – 
11) category for CO, NOX, and VOC.


Between 3/23/2005 and 7/18/2005 a new SCC to Tier Structure was developed.  To 
obtain the .xls SCC to Tier file dated June 2005, go to the CHIEF website at: 
http://www.epa.gov/ttn/chief/codes/index.html#tier 

The most notable change is for the PM pollutant codes.  Some SCC’s that were in the 
Miscellaneous category (Tier1 – 14) in the previous SCC to Tier Structure were moved to 
the Other Industrial Processes category (Tier1 – 07) in the new SCC to Tier Structure.  
The change in Tier Structure was made for the years 1990, and 1996-2002 and did not 
affect National totals.  The 2002 numbers in the 7/18/2005 Trends Report are still the 
Preliminary version for 2002, not the Draft version of 2002.