Blood lead is generally believed that the relative safety standards should not exceed 10 micrograms to 14 micrograms / liter; long-term inhalation exposure to metallic lead or lead compounds in dust, can cause varying degrees of [lead poisoning] disease (serum concentration greater than 40 micrograms of lead / l); inhaled too much will harm the human nervous system, heart and respiratory system, causing varying degrees of lead poisoning; the human body, can lead to interference with a variety of enzymes with a wide range of physiological activities organisms, leading the body organ harm; the chance of lead poisoning in children is far more than adults.