垃圾焚烧毒灰对食品安全的威胁

2020/1/7 11:09:59

有关塑料、垃圾焚烧和飞灰的简介

我们生活在塑料时代。塑料无处不在,即使在最原始的地方,我们也能找到一些细小的塑料碎片。大多数塑料是由化学家发明的。并且,为了使塑料适用于不同的用途或例如使塑料符合防火安全的法律要求,塑料需要添加化学添加剂使其具有耐性、柔韧性、耐用性或不那么易燃。这些添加剂很多本身是有毒的,且燃烧时也会产生新的化学物质。这些新的化学物质可能比原来的添加剂毒性更大。

像聚氯乙烯(PVC)这样的氯化塑料燃烧后会生成氯化二噁英(Stockholm Convention on POPs 2008),而非氯化塑料燃烧后仍会产生其他有毒的持久性化学物质,如多环芳烃(PAHs)。

众所周知,塑料的生产和使用过程,及其处置过程  (Hahladakis, Velis et al. 2018, Basel Convention Secretariat and Stockholm Convention Secretariat 2019),特别是燃烧或焚烧过程中 (Blankenship, Chang et al. 1994, Thornton, McCally et al. 1996, Yasuhara, Katami et al. 2006, Stockholm Convention on POPs 2008),都会有有毒化学品会释放到环境中。为了避免和/或至少减少二噁英从垃圾焚烧厂直接排放到空气中的情况,人们发明了特殊的洗涤器,但这并不意味着塑料垃圾焚烧(WI)不会导致二噁英排放到环境中。二噁英在飞灰和其他空气污染控制(APC)残渣中累积。为了简单起见,我们在本报告中称它们为飞灰。

跟进关注这些残渣的后续处理很重要。如果处理不当,二噁英可能会从这些残渣中释放到土壤或水中。二噁英也可能伴随着灰尘飘向远处。此外,来自垃圾焚烧残渣的二噁英渗滤液(Kim and Lee 2002, Kim and Osako 2004)也会是一个释放到环境中的途径(另见本报告第7章)。

在复杂的垃圾焚烧炉、垃圾能源化工厂和/或垃圾—燃料转化设施******烧塑料,会产生大量含有氯化二噁英以及其他持久性有机污染物(POPs)如溴化二噁英的灰渣。溴化二噁英是焚烧含有溴化阻燃剂(BFRs)的塑料产生的。本报告第8章列出了不同持久性有机污染物在飞灰中所含的比例。其中许多持久性有机污染物与氯化二噁英的毒性相似。需要指出的是,有几项研究证明,一些不太复杂的塑料焚烧也会产生含有持久性有机污染物的灰烬 (Fiedler 2001, Petrlik and Khwaja 2006, Mochungong 2011, Petrlik, Adu-Kumi et al. 2019)。

本报告公开披露了垃圾焚烧污染的现实,并提出了强有力的论据,支持逐步淘汰垃圾焚烧,转而采用非燃烧的垃圾处理技术和可持续的垃圾管理方式。报告还明确指出,需要在全球环境公约中确立严格的低持久性有机污染物含量水平,以防止有毒垃圾越境转移到低收入国家,以及对环境有害的焚烧残渣在所有国家的分布。

我们回顾了近300篇关于垃圾焚烧残渣的主要研究和文章,发现飞灰有被用作道路的建筑材料、用于河堤或海堤、水泥或砖块,甚至用作农业土壤的改良剂。所有这些用途,在本报告第5章有详细阐述,会导致二噁英和其他持久性有机污染物释放到环境,污染食物链的高风险。报告第九章对世界各地危险使用垃圾焚烧产生的飞灰的案例进行了研究,其中包括了英国纽卡斯尔的著名案例。第11章描述和讨论了二噁英和类二噁英的化合物污染食物链的不同情况。

在几个实际案例中,处理/处置含有20至12000pg TEQ/g二噁英的废弃物,会导致食物链(鸡蛋或禽肉)的污染水平高于欧盟建议的食品中二噁英含量限值(2.5 pg TEQ/g脂肪)的20倍以上。参考点(背景值水平)的散养鸡蛋中的含量超过280倍。那些来自非洲、亚洲和欧洲的案例在单独发表的研究中进行了描述(Katima, Bell et al. 2018, Petrlik, Adu-Kumi et al. 2019)。

基于食物链污染的情况,报告撰写人员建议对持久性有机污染物(有害)废物的定义设定更严格的限值,即二噁英和类二噁英多氯联苯的含量为1ppb(ng TEQ /g)。没有稳定化后在地表使用的话,限值为0.05 ppb (ng TEQ /g)。第12章讨论了立法措施。

第14章讨论了垃圾焚烧残渣的处理的替代措施。第15章讨论了和垃圾管理(包括塑料垃圾)的替代措施。

这份报告显示,增加垃圾焚烧并不能解决当前的塑料危机,它只是将有毒化学物质从排放到空气中转移到无法控制的废弃物流中。我们还发现,问题的规模比估计的要大。本报告估计的废弃物中含有的7- 10kg的二噁英,占排放或转移到环境中的二噁英总量的很大一部分。如塑料行业建议的那样,这一含量可能会随着塑料垃圾的增加而显著增加(Goldsberry 2019)。

燃烧经溴化阻燃剂处理的塑料会有产生溴化二噁英的风险,其毒性与氯化二噁英相似。最近,在加纳首都阿克拉(Accra)的阿博布罗西(Agbogbloshie)的电子垃圾废料场采样的土鸡蛋中发现了高含量的溴化二噁英(Petrlik, Hogarh et al. 2019),在中国武汉市垃圾焚烧厂附近采样的鸡蛋中的溴化二噁英含量也不低(Petrlik 2016)。在这两种情况下,溴化二噁英的含量都超过了欧盟标准规定的食用鸡蛋中氯化二噁英的含量数倍(European Commission 2011)。垃圾焚烧的底灰被认为聚集了高浓度的溴化二噁英(Wang, Hsi et al. 2010, Tu, Wu et al. 2011)。

不加控制地使用垃圾焚烧产生的飞灰及其整体毒性突出表明了在其生命周期开始时就处理塑料垃圾的必要性。根据最近的研究预测(Geyer, Jambeck et al. 2017, Guglielmi 2017),未来30年的塑料垃圾产量比以往产生的要多4倍。而鉴于大量焚烧塑料垃圾所产生的有毒灰烬越来越多,继续增加塑料产量(Laville 2019, Tullo 2019)的做法是无法接受的。燃烧1吨固体垃圾可产生约300公斤含有氯化二噁英和溴化二噁英的垃圾焚烧残余物。

图x:塑料垃圾生产和处置的历史数据和到2050年的预测。“初级垃圾”是指塑料第一次变成垃圾,不包括已回收的塑料垃圾。

来源: (Geyer, Jambeck et al. 2017, Guglielmi 2017)

塑料不仅仅是塑料工业所宣称的垃圾管理问题(Dunn 2019)。它必须通过在第一阶段实现其产量的最小化来解决。较少的塑料燃烧也会减少产生大量含有持久性有机污染物的有毒垃圾焚烧残渣。


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报告下载链接:垃圾焚烧毒灰对食品安全的威胁