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2016年1月7日 11:22  阅读 2346
Scientists warn of dangers of multi-toxin Bt crops

翻译:jrry86;原文发表时间:2015年12月7日;原文链接: //www.gmwatch.org/news/latest-news/16583-scientists-warn-of-dangers-of-multi-toxin-bt-crops

对转基因的警告,看看吧! Hazards to non-target insects and mammals from multi-trait Bt insecticidal crops are being ignored by regulators, a new scientific review shows. Claire Robinson reports
最新的科学综述显示,多抗Bt抗虫转基因作物对非标靶昆虫和哺乳动物的危害一直都被管理机构忽视。Claire Robinson报道

An increasing number of “stacked-trait” GM Bt insecticidal crops combining several Bt toxins in one variety are coming onto the market. We’re assured that they’re safe. But evidence presented in a comprehensive new review throws this claim into question.
越来越多的将多种Bt毒素整合进同一个品种的多抗转基因Bt抗虫作物正进入市场。我们被告知它们是安全的。但是一篇最新综述( //journal.frontiersin.org/article/10.3389/fenvs.2015.00071/abstract )提供的证据使该主张受到质疑。

Stacked-trait GM crops are produced by cross-breeding single or double-trait GM Bt crops. They have been approved as safe based on several assumptions.

For example, individual Bt toxins are often thought only to harm a few target insect pests and not to affect non-target and beneficial organisms, like ladybirds and lacewings. Also, regulators accept the argument from the industry and allied scientists that if the single Bt toxins included in the stacked crop are individually deemed safe, a combination of several Bt toxins and other GM traits present in stacked GM Bt crops will also be safe.
例如,通常认为单个Bt毒素只杀死一些标靶害虫,而不影响非标靶昆虫及益虫,如瓢虫和草蛉。并且监管机构也认可( //www.testbiotech.org/sites/default/files/SmartStax_Bt_Synergies_Testbiotech.pdf )业界及其联盟科学家的说法,即如果多抗作物中引入的Bt毒素在单独存在时是安全的,则把多个这样的Bt毒素以及其它转基因特性组合在一起,得到的多抗转基因Bt作物也一样安全。

But these assumptions are shown to be false by scientific evidence, the new review shows. The authors, Angelika Hilbeck of the Swiss Federal Institute of Technology and Mathias Otto of the German Federal Agency for Nature Conservation, reviewed the scientific literature for evidence of Bt toxin effects on non-target organisms and for combined effects of several Bt toxins acting together. Then they compared their findings to the regulatory dossiers provided by industry to support approval of stacked-trait GMOs.
但是这篇新的综述显示有科学证据证明这些假设是错误的。文章作者,瑞士联邦技术学院的Angelika Hilbeck和德国联邦自然保护机构的Mathias Otto,综合分析了科学文献中的Bt毒素对非标靶生物的影响以及多种Bt毒素同时作用的协同效应。他们还将研究结果与业界为向监管部门申请批准多抗转基因作物而提供的档案材料作了比较。

Their findings make for sobering reading.

Bt toxins don’t only affect certain insect pests

First, Hilbeck and Otto addressed the declaration made by industry and regulators that Bt toxins are specific to certain insect pests and no documented cases of non-target effects on beneficial insects exist. They found that the evidence points to the opposite conclusion. Research studies show that individual Bt toxins can have harmful effects on beneficial and non-target organisms. But the industry dossiers submitted to regulators ignore these studies and maintain the fiction that Bt toxins only harm the target insect pests.

Lead researcher Hilbeck commented in an interview, “The notion of a narrow specificity for Bt toxins is not true. Those who talk of narrow specificity base this on a narrow definition of an effect – the ‘quick kill’ effect.

“This is an economic concept: you want a quick kill for economic reasons, to save the crop from pest-induced damage.

“But Bt toxins are not fast-acting toxins. Even in target pests, Bt toxins don’t kill quickly – it takes most susceptible insects a day or more to die. The Bt toxin in GM crops is expressed in the crop plant for months at a time. Residues linger in soil and aquatic systems.

“Regulatory tests need to look at long-term and sublethal effects, because that is what non-target organisms are likely to be exposed to. Currently these tests are not required. Yet we found a lot of evidence in the scientific literature that non-target organisms such as ladybirds, water fleas, lacewings and even slugs are adversely affected by Bt toxins.”

Hilbeck warns that mammals may be affected, too. She mentions a separate newly published review, which concluded that Bt toxins “cannot be considered innocuous, as they have some physiological effects that may become pathological”.
Hilbeck警告说哺乳动物也会受到影响。她提到了另一个新发表的综述,该综述作出结论( //www.ncbi.nlm.nih.gov/pubmed/26537666 )说“不能认为Bt毒素是无害的,因为它们会对生理带来一些影响,并可能导致病理反应。”

Hilbeck suggests a direction for future research on non-targets: “We have to extend the definition of ‘effect’ from the economic to the ecological.” She believes that pre-market safety testing should include long-term animal feeding studies with the complete stacked-trait crop. Currently these are not required by any regulator in the world.

“Drastically increased” Bt toxin load

Another commonly ignored issue in risk assessment of stacked-trait Bt crops is the large amount of Bt toxins expressed in them – which is far higher than in single-trait Bt crops. Together, the pyramid of different Bt toxins go to make up what the researchers call a “drastically increased” Bt toxin load.

And in spite of frequent claims that Bt crops reduce or eliminate pesticides, stacked-trait Bt crops contain far more insecticide than the amount of chemical insecticide that is supposed to be displaced. For example, SmartStax GM maize contains six different Bt toxins (as well as two herbicide-tolerant traits). The total Bt insecticidal protein production of the crop is estimated at 4.2 kgs/ha, 19 times the average conventional insecticide rate of application in 2010.
而且,尽管频繁宣传Bt作物可以减少甚至消除农药的使用,多抗Bt作物中所含有的杀虫剂远比理论上它们所能取代的化学杀虫剂多得多。例如,SmartStax转基因玉米含有六种( //www.testbiotech.org/sites/default/files/Background_TBT_ Imports_SmartStax.pdf )不同的Bt毒素(还具有两种抗除草剂特性)。据估计( //www.enveurope.com/content/24/1/24 ),每公顷该作物表达的Bt杀虫剂总量为4.2公斤,是2010年常规杀虫剂平均使用量的19倍。

Yet SmartStax stacked-trait maize was approved for EU food and feed imports without thorough safety testing of the whole GM crop containing the complete Bt toxin package in laboratory animals or non-target organisms. In an interview, Hilbeck commented that only the individual isolated Bt toxins that went into developing the stacked-trait crop may have been tested by industry for short-term safety in few insect feeding trials.
可是欧盟在没有彻底评估完整的含有全套Bt毒素的多抗SmartStax转基因玉米对实验动物和非标靶生物的安全性的情况下,仍然批准( //www.testbiotech.org/en/node/940 )了其进口,用作食品和饲料。在采访中,Hilbeck评论道,组成多抗作物的多种Bt毒素,只有单个独立的毒素可能经由业界作了少量短期昆虫喂养安全试验。

Combination toxic effects ignored

As well as the increased amount of Bt toxins found in stacked-trait crops, there is also the question of whether potential interactions and combined toxic effects of the different GM traits and chemical residues contained in stacked-trait Bt crops could harm consumers and non-target insects. And both GM and non-GM seeds are often treated with neonicotinoid insecticides, which add to the cocktail of known and potential toxins.

In spite of these biological and chemical “cocktail” risks, Hilbeck and Otto say that most regulators, including the European Food Safety Authority (EFSA), still limit the environmental risk assessment of stacked-trait Bt crops to consider one Bt toxin at a time, in isolation. And that single Bt toxin is tested not as it is expressed in the GM Bt crop plant, but only as a single purified protein produced in bacteria, in testing schemes developed for the regulatory approval of acute toxins like synthetic insecticides.

The independent research group Testbiotech has previously warned that combination and synergistic effects of the elements in stacked-trait crops are being ignored by regulators.
独立研究小组Testbiotech以前就曾警告( //www.testbiotech.org/sites/default/files/SmartStax_Bt_Synergies_Testbiotech.pdf )说监管者忽视了多抗作物中各元素的叠加和协同效应。

That view is backed by first-hand experience of the author of this article at a public meeting of the European Food Safety Authority (EFSA), which issues safety opinions on GM foods and pesticides. A member of the EFSA GMO Panel asserted without qualification that the various GM traits and chemical residues combined in any authorized GMO stacked-trait crop “will not interact”. When challenged, the panel member presented no evidence for this broad claim.

Hilbeck and Otto put such claims to the test. They searched the literature for research on the combined and synergistic effects on beneficial and non-target organisms of multiple Bt toxins, or of Bt toxins together with other proteins, chemicals, or plant components. They found a number of studies showing interactions and combined effects, the mechanisms of which are not fully understood.

Crucially, in a finding that directly challenges EFSA’s reductionist “one-at-a-time” approach to stacked-trait crops, Hilbeck and Otto discovered that many synergistic interactions in target organisms were not predictable from single trait effects. They occurred when the individual components tested in isolation did not elicit a response at all or elicited only a sublethal response.

Modes of action of Bt toxins getting murkier over time

The assumed safety of Bt toxins for non-targets and human and animal consumers largely rests on their claimed specificity to insect pests. But this claim in turn rests on research on a narrow set of target insect pests, studying mostly a single type of Bt toxin.

And as scientific research and knowledge has grown, uncertainty about how Bt toxins exert their effects has increased. Hilbeck and Otto state in their paper that today there is “less scientific certainty” about Bt toxins’ mode of action than when Bt toxin genes were first engineered into GM plants 30 years ago.
随着科研和知识的增加,对Bt如何发挥作用的不确定性也在增大。Hilbeck和Otto在文章中陈述道,相比于30年前Bt 毒素基因首次转入转基因作物时,今天人们对Bt毒素的作用机理“在科学上更加不确定”。

The situation is made even murkier by the fact that one of the most promoted of possible modes of action has been cast into doubt by a case of apparent scientific misconduct. In 2012 it emerged that the researchers who came up with the proposal, husband and wife team Alejandra Bravo and Mario Soberon, had manipulated images in 11 papers. The researchers had offered the images as evidence for their proposed mode of action for Bt toxins. They have at least one patent related to their work.
这一状况又因为一个明显的科学舞弊行为而变得更为混乱,导致一直最被推崇的Bt的可能作用机理受到了质疑。2012年,提出此作用机理的夫妻档科学家Alejandra Bravo和Mario Soberon被发现( //retractionwatch.com/2012/11/23/university-disciplines-researchers-who-study-toxins-used-in-gmo-crops-at-least-seven-corrections-to-follow/ )篡改了11篇文章中的图片。他们用这些图片作为他们提出的Bt作用机理的证据。他们还至少拥有一个与此研究有关的专利( https://register.epo.org/application?number=EP07747214 )。

The episode resulted in seven journals agreeing to publish corrections and to Bravo and Oberon resigning from chair positions they held at the National Autonomous University of Mexico.

Their model for Bt toxins’ mode of action has been critiqued by a Canadian team of researchers as “difficult to reconcile” with evidence generated by other investigations. The Canadian team concluded, “Many important questions concerning the mechanism by which insect cells are killed by Bt toxins remain just as poorly understood as they were before these models were put forward.”
他们提出的Bt毒素的作用机理模型受到一个加拿大科研团队的批评( //www.sciencedirect.com/science/article/pii/S0022201112001358 ),认为它难以与其他研究者得到的证据吻合。这个加拿大团队总结到,“很多与昆虫细胞如何被Bt毒素杀死的机理有关的重要问题都还没搞清楚,这与这些模型被提出之前的状况一样。”

The sum of known and unknown factors about GM Bt toxins lead Hilbeck and Otto to conclude that while stacked GM crops may offer benefits to some farmers, “these benefits may come with serious health and environmental risks” that should be experimentally studied before market approval. They recommend a “comprehensive examination of the systems, organs, tissues and cells” of non-target organisms and animal and human consumers, “especially the gastrointestinal tract, the immune system, the genitourinary tract and the respiratory and nervous systems.” They also call for further studies on the sub-chronic, chronic and immunotoxicological effects of Bt toxins, particularly on humans.

Review article: Specificity and combinatorial Effects of Bacillus thuringiensis Cry toxins in the Context of GMO environmental risk assessment
Angelika Hilbeck and Mathias Otto
Front. Environ. Sci., 9 November 2015   //dx.doi.org/10.3389/fenvs.2015.00071

Stacked GM crops expressing up to six Cry toxins from Bacillus thuringiensis (Bt) are today replacing the formerly grown single-transgene GM crop varieties. Stacking of multiple Cry toxins not only increase the environmental load of toxins but also raise the question on how possible interactions of the toxins can be assessed for risk assessment, which is mandatory for GM crops. However, no operational guidelines for a testing strategy or testing procedures exist. From the developers point of view, little data testing for combinatorial effects of Cry toxins is necessary as the range of possibly affected organisms focuses on pest species and no evidence is claimed to exist pointing to combinatorial effects on non-target organisms. We have examined this rationale critically using information reported in the scientific literature. To do so, we address the hypothesis of narrow specificity of Cry toxins subdivided into three underlying different conceptual conditions (i) “efficacy” in target pests as indicator for “narrow specificity,” (ii) lack of reported adverse effects of Cry toxins on non-target organisms, and (iii) proposed modes of action of Cry toxins (or the lack thereof) as mechanisms underlying the reported activity/efficacy/specificity of Cry toxins. Complementary to this information, we evaluate reports about outcomes of combinatorial effect testing of Cry toxins in the scientific literature and relate those findings to the practice of environmental risk assessment of Bt-crops in general and of stacked Bt-events in particular.

综述文章:Bt Cry毒素在环境风险评估中的特异性和协同效应
作者:Angelika Hilbeck和Mathias Otto
《环境科学前沿》,2015年11月9日,链接: //dx.doi.org/10.3389/fenvs.2015.00071