1971年9月29日。美国EPA(环境保护局)公布了一个新的大气质量标准—空气中的铅为1.5mg/m~(?)。新标准是为了防止儿童血液中的铅含量达到30mg/分升血这一指标而制定的。据EPA调查,在一般居民中1～5岁的儿童对接触铅最为敏感,1970年,美国共有2千万1～5岁的儿童,其中有一千二百万居住在都市地区,有5百万住在市中心,对铅的接触最 September 29, 1971. The United States EPA (Environmental Protection Agency) announced a new air quality standard - lead in the air of 1.5mg / m ~ (?). The new standard is to prevent the lead in children’s blood lead to 30mg / min of blood to develop this indicator. According to the EPA survey, 1 to 5-year-old children are the most sensitive to lead exposure in the general population. In 1970, there were 20 million children between the ages of 1 and 5 in the United States, of which 12 million live in metropolitan areas and 5% Live in the city center, the most exposure to lead