Dust storms are common in parts of the world with dry land areas such as Middle East. They are caused by great wind velocity. Periods of severe and widespread drought can increase the likelihood of major dust storms,particularly during the summer months. Dust storms are caused by a combination of weather conditions (low rainfall),features of the natural environment and human activity. Dust storm events,especially strong dust storms are not only immediately dangerous,but may also have a long-term,harmful effect.