Effects of linear pollution source position and the number on the maximum pollutant concentration are numerically investigated. It is found that the lowest effect of pollutants is produced when their sources are placed near the street center or closer to the windward side. When the number of sources increases up to four at constant total emission intensity, the maximum pollutant concentration grows providing the sources are located symmetrically inside the street canyon. If the source, the nearest to the leeward side of the street, is located at equal distances from buildings, then the maximum concentration of pollutants decreases independently of the number of such sources.