孩子血液里没有安全的铅含量：疾控中心参考值是3.5微克，参加医疗补助的孩子1岁和2岁必须查血铅
美国疾病控制与预防中心（CDC）说得很直白：到目前为止，还没有发现对儿童安全的血铅水平，哪怕很低的血铅也会影响孩子的健康。麻烦的是，铅中毒的孩子大多看不出明显症状，想知道孩子有没有接触过铅，唯一可靠的办法是验血，所以 CDC 把血铅检测列为儿童铅中毒预防的第一步。
判断结果高低，CDC 用一个参考值：每分升血液3.5微克（3.5 μg/dL）。这个数字来自全国健康与营养调查中1到5岁儿童血铅值的第97.5百分位，意思是孩子的血铅达到或超过3.5，就已经站在全美同龄孩子里血铅最高的2.5%那一档，医生会安排复查和后续服务。参考值不是安全线，低于它也不等于没接触过铅。
哪些孩子要优先查，CDC 列了几类：住在或常去1978年之前建的老房子的孩子，老房子是铅漆和铅尘最常见的来源；低收入家庭的孩子；来自欠发达国家的移民、难民和新领养儿童；家里有人从事接触铅的工作或有接触铅的爱好。参加联邦医疗补助（Medicaid）的孩子是硬性要求，必须在12个月和24个月大时各查一次，24到72个月之间从没查过的也要补查，检测费用由联邦医疗保险与医疗补助服务中心承担；很多私人保险也覆盖血铅检测。
检测有两种：指尖或脚跟取血的毛细血管检测出结果快，通常先用它筛查，但皮肤上沾的铅可能让结果偏高，超过参考值要用静脉抽血复核确认。确认血铅偏高后，医生会建议找出并清除孩子生活环境里的铅源，给孩子多吃富含铁和钙的食物，并安排后续复查和早期教育服务。家长拿不准孩子要不要查，直接问儿科医生，就是 CDC 给的建议。（来源：美国疾病控制与预防中心）
There Is No Safe Level of Lead in a Child's Blood: CDC's Reference Value Is 3.5 Micrograms, and Medicaid Children Must Be Tested at Ages 1 and 2
The Centers for Disease Control and Prevention (CDC) states it plainly: no safe level of lead in children's blood has been identified, and even low levels can negatively affect a child's health. The difficulty is that most children with lead in their blood have no obvious immediate symptoms, so the only reliable way to know whether a child has been exposed is a blood lead test, which CDC puts at the center of childhood lead poisoning prevention.
Results are read against CDC's blood lead reference value of 3.5 micrograms per deciliter (3.5 μg/dL). The value is set at the 97.5th percentile of blood lead levels among U.S. children ages 1 to 5 in national survey data, so a child at or above 3.5 μg/dL is in the top 2.5 percent of blood lead levels nationwide and should receive confirmatory testing and follow-up services. The reference value is a screening tool, not a safety line: a result below it does not mean a child has had no lead exposure.
CDC lists the children who should be screened first: children who live or spend time in a house or building built before 1978, the most common source of lead paint and lead dust; children from low-income households; immigrant, refugee and recently adopted children from less developed countries; and children who live or spend time with someone who works with lead or has hobbies that expose them to lead. For children enrolled in Medicaid the test is mandatory at ages 12 and 24 months, and again between 24 and 72 months if the child was never tested, with the cost covered by the Centers for Medicare & Medicaid Services; many private insurance policies also cover blood lead testing.
Two kinds of tests are used. A finger-prick or heel-prick capillary test gives fast results and is usually the first step, but lead on the skin can push a result high, so a value above the reference value is confirmed with a venous blood draw. If a child's level is confirmed above the reference value, the doctor may recommend finding and removing lead from the child's environment, a diet high in iron and calcium, follow-up blood testing and connection to early educational services. Parents who are unsure whether their child needs testing should ask the child's health care provider, which is CDC's own advice. (Source: Centers for Disease Control and Prevention)
来源：美国疾病控制与预防中心
发布：GSM·美国（发布链接）
图片来源：Wikimedia Commons 摄影，CC BY-SA 4.0：工人为住宅清除含铅油漆（示意：1978年前住房的铅漆须专业处理）
GSM Global · 本篇英文版 English edition of this story
