June 2009
Front Matter
Training
36
NATTS Sampling
Overview
•NATTS sampling began in 2003 with 23 sites; the first complete year of data was 2004. The principal objective of the NATTS network is to provide long-term monitoring data across representative areas of the country for certain priority HAPs (e.g., benzene, formaldehyde,
1,3-butadiene, acrolein, and hexavalent chromium) in order to establish national trends for these and other HAPs.
June 2008
There are currently 27 national air toxics trends sites: 21 urban and 6 rural.
Most stations are collocated with PM2.5  speciation samplers, and some also
include PAMS measurements.
Recently, the list of pollutants monitored at NATTS sites was expanded to include polycyclic aromatic hydrocarbons (PAHs), of which naphthalene is the most prevalent.
All sites follow QA programs for sampling and siting.
Periodic refinement of pollutants and/or sampling may be made (e.g., EPA plans to re-evaluate the program every six years).