APM can be described as a mixture of solid and liquid particles suspended in a gaseous state (air). Generally, the size frequency of the particles has a distribution, with two main peaks at about 0.2 micrometers and at about 10 micrometers. One can also classify particles sizes according to sources of origin. Particles of a size less than 2 micrometers can be attributed mainly to combustion processes (anthropogenic activity) or gas-to-particle conversion. Particles larger than 2 micrometers are mostly derived from mechanical processes (e.g. soil erosion) or incomplete combustion (IAEA: Parr et al. 1996). The uncertainty in fine particulate aerosols concentrations and chemistry' significantly limits are ability to assess the effect of natural human induced changes on global climate forcing and human health (Cohen et al, 2002)