铅，衰老和死亡

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GLASS 代表全球铅劝告和支援的服务机构
GLASS 提供资料和推荐关于铅中毒和铅污染的预防和处理，
目地是要全球性的根除铅中毒和保护环境免受铅的影响。GLASS由前小组公司管理。
ABN 号码是25819463114, 文章编号

[LID 9507]

Lead, Ageing and Death

铅，衰老和死亡

By Ewan MacAulay McDonnell, The LEAD Group Inc
由伊凡麦考雷麦当劳编写，铅小组公司

Translated into Chinese (Mandarin) by Hugh Xin Xi Zhu, Physician
由修．心禧．朱医师翻译成中文

当老年人死亡时，谁曾问过这个问题-“是铅杀死了这个人吗？”

随着年老，你更容易患上心脏病，心脏病发作，中风，肾脏问题，阿尔茨海墨氏病或震颤。但是，你可能认识不到这些症状是与你体内含有铅相关的。

现在与过去相比，因为很多人都含有更高的血铅水平，所以我们把衰老和铅中毒的许多作用联系在一起其实并不奇怪。特别是不良的记忆力和听力，摔交（由于失去平衡），精虫数目减少，性欲减退，中风，心脏病突发（由高血压引起的），蛀牙及阿尔次海墨氏病。公正地说，所有这些铅作用加起来可以合理地描述我们所认为的“正常”衰老。当然，我们测量有这些症状的老人的血铅浓度的时间是在折扣他们的症状仅是“自然变老的部分”之前。

伴随着铅接触，铅量在你的体内不断堆积。这种堆积是没有安全水平的。而且，随着资料的完善以及进一步的研究，安全铅水平的阈值几十年来已经逐渐地有所降低。美国国家疾病控制和预防中心（CDC）当前所列的阈值是<10微克/分升，然而，更近的研究显示即使当铅水平低至2.5微克/分升时，仍会对身体健康产生损害，而且其损害更甚于10-20微克/份升或20-30微克/分升的铅水平。

根据近期《内科档案》中的一篇文章，“血铅和贯穿生命的铅接触同提高了的老年人死亡率已经被联系在了一起”。在调整了潜在的混乱因素后，与那些血铅水平低于10微克/分升（<0.5微克分子/升）的人相比，血铅浓度达到20-29微克/分升（1.0-1.4微克分子/升） [比疾病控制和预防中心所制定的低于10微克/分升的这一目标高出了2到3倍，但仍远低于铅浓度50微克/分升，这项用以强制澳大利亚工人撤离铅接触工作环境的标准] 这一基线的个人，其死亡率增加了46%（由所有原因引起的）；由循环系统引起的死亡率提高了39%；由癌症引起的死亡率增加了68%。

实际上，根据美国国家疾病控制和预防中心的一项研究，2微克/分升的血铅水平就已与较高的心血管发病率有关。3.63微克/分升或更高的血铅水平会将心脏病发作引起的死亡率提高89%；将中风发作率提高250%。血铅水平高于10微克/分升的成年人中发现有较高的动脉硬化患病率。

当铅开始在骨内沉积，骨头起到了‘蓄水池’的作用。从那里，血铅对血红素合成，维生素D代谢，肾脏功能起到了第二轮的负面影响。首先，铅是一种神经毒素，它能引起与阿尔茨海墨氏病相似的症状。由于病因相同，所以与该病有关。如果从儿童时期起就有铅接触，基因表达会在你今后的生活中造成其他的健康问题，其中包括脑部蛋白质堆积，其形式与阿尔海墨氏病引起的相似。累积的铅接触也与老年人较低的学习，记忆，视觉及运动能力有关。另外，压力能够加剧这种负面影响。不佳的学习表现可能是儿童早期的铅接触导致的，也可能是铅在包裹脑内神经元的髓磷脂鞘中堆积，从而引发的神经变性疾病。最近的一项研究显示，患者平均的血铅水平为3.5微克/分升，胫骨铅水平为18.7微克/分升。而较高的胫骨铅水平和不良的认知功能是密切相关的。

另一种可能与铅有关的神经性疾病是原发性震颤（ET）。原发性震颤是一种不可治愈的，与衰老相关的疾病，其症状涉及到手和头部的震颤。目前，它的成因仍不为人知。用于实验的动物和接触了高铅环境的人已经表现有相似的症状。原发性震颤患者的血铅水平已发现高于其对照组。原发性震颤在年龄大于60岁的实验者中是一种很常见的神经性疾病，其比例可高达20.5%。

铅加速着大脑的老化，而当你衰老时，骨头不断地脱去矿质，这意味着它们把铅释放回血流当中。那么，在你年轻时发生的铅接触（例如处理含有铅成分的油漆或汽油之类的工业工作）所产生的毒性作用，将综合你现在正经受着的铅接触，累加起来对你的身体健康造成危害。一生中已经在工作场所或家中有铅接触的成年人更容易患上与铅相关的疾病，如心血管病，高血压，中风，肾功能衰竭及骨质疏松。

一些涉及到早年铅接触的经绝期妇女也接受了测试。结果显示，贯穿生命的铅接触可导致绝经期的高血铅。有些研究还发现激素替代疗法（HRT）有抑制血铅浓度的作用。使用激素替代疗法的妇女比较经绝期没有使用激素替代疗法的妇女有更低的血铅浓度。

有一份专题报告书对各类人群，包括‘儿童’，‘产前发育和生殖健康的作用’及‘成人’的铅中毒做了全面的描述。列在不同组的这些人涉及到多种铅中毒，包括神经系统，周围神经系统，成长和发育，认知的发育，行为，听觉，视觉，运动和肌肉，消化系统，胎儿，肾脏，心脏血管及血液循环，智力和脑力，感觉，骨骼，肌肉和关节，还有死亡。另外，这个报告书还列出了从动物实验中得出的各种铅作用（参见网页 www.lead.org.au/fs/fst7.html ）。

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