【明報專訊】YESTERDAY, because Hong Kong was affected by a sandstorm from Mongolia, the air pollution index (API) went off the chart - exceeded 500 - in many places in the territory for the first time since 1999, when the index was introduced. That affected citizens' life. There is nothing man can do about dusty weather or weather changes. However, prompt precautions may lessen their effects. The fact that Hong Kong suddenly encountered dusty weather yesterday shows Hong Kong Observatory operates an inadequate early warning system and the Environmental Protection Department (EPD) lacks foresight. Both must improve their systems and practices.