We have employed Compton supression neutron activation analysis in conjunction with thermal and epithermal neutrons to detemine
trace elements in airborne particulate matter in Lisbon, Portugal. As a result of the proximity of ocean marine, elements
such as sodium and chlorine can signficantly decrease the analytical sensitivities of many elements of interest due ot the
high backgrounds arising from 38Cl and 24Na. Compton suppression has resulted in the increase of the analytical sensitivities using thermal neutrons of Al, Ba, Ce,
Cr, Cu, Ni, Rb, Se, Th, Ti, V, and Zn. The use of Compton suppression and epithermal neutrons significantly reduced the detection
limits for As, I, K, Si, and W, while the utilization of solely epithermal neutrons improved the analyses of In.