A research on evaluation of dust/clay colloids (diameter size 0.002/0.0002mm) i.e. PM 2.5 (less tha 2.5 m size diameter) contaminations to air were investigated where major sources of dusts/clays from soils of various categories were reported. Such dust/clay colloids contaminations occurred by CO2, CO, SO2, SOx, N2O, NOx, heavy metals like Pb, As, Cd, Cr, Ni, Hg, Co, etc move in air although soil has 16-24 heavy metals contaminants with various concentrations. Again, Coal-fired power plants carry lots of heavy metals like Zn, Se, Cd, Ni, Pb, Hg, Cr, V, Br, As, Ur, Ti, CO2, CH4, NOx although most N2O, N, NOx etc. come from N-fertilizers. Such minor to major polluted/contaminated dust/dust colloids in air move/enter the human body as toxic/contaminated air and acts as slow poison and producing minor to major diseases including cancer. Here dusts related diseases (more than 20) are listed. Again, dust sources, contaminations and health hazards were also compared between developed countries and Bangladesh. Air is not fresh one at Dhaka i.e. air at Dhaka city means dust/dust colloid contaminated air. The satellite observation of PM 2.5 or more may or may not be severely contaminated until lab. analysis and detections covering of various heavy metals, widely used pesticide residues/contaminants and other pollutants in air although black dust/fume dusts carry huge contaminants. Finally, wide suggestions and recommendation are applied against dust contaminations in air. The entire study, observations, measurement guidelines are well analysed through five tables (Tables 1-5) and five figures (Figs. 1-5) and they are summarized and presented as schematic model in Fig. 1.

Key words: Dusts, dust colloids, clay colloids, contaminations, problems, health hazards, sources of dust contaminations, comparisons, heavy metals, suggestion/guidelines.