by Jonathan Latham, PhD
Imagine you are an undergraduate attending an Ivy League university. You go to a routine department seminar. In the middle of his presentation the professor picks up a container from the lectern. He says it contains a pesticide. As he opens it, a faint cloud of brown powder rises from the tub. It is, says he, “very safe”. Then he digs his finger into the container and tastes some of the contents. He offers it to a man in the front row, who twice refuses it. Walking back to the centre of the room, the professor looks towards you and pushes the container in your direction.
Apparently he wants you to join him in eating pesticide. What should you do?
This scene does not need to be imagined. Here is the clip:
It occurred at a Cornell University department seminar titled: “Biotechnology Is Helping Resource Poor Eggplant Farmers in Bangladesh–So why is GMWatch Against It?” that took place in March, 2019.
The pesticide in question is the insecticide Dipel.
Dipel is the proprietary name for a preparation derived from fermenting the bacterium Bacillus thuringiensis (var. Kurstaki). B. thuringiensis is a gut pathogen of many species, including humans (McIntyre, et al., 2008; Latham et al., 2017).
Dipel is obtained by partially purifying the fermented mixture so that the final pesticide is composed of several different Cry toxins (which are considered to be the active ingredients), along with bacterial cell spores and cell debris. Dipel and similar products have long been used in spray programmes against forest and agricultural pests. Dipel is also used in organic agriculture.
Consuming Dipel has health, ethical and legal implications
Feeding Dipel to one’s students creates an impressive list of problematic issues. They include safety concerns, ethics concerns, questionable science, and, not least, by eating a pesticide and encouraging his students to do the same, the professor and his students broke the law.
Beginning with science, one can ask what scientific point is demonstrated by eating a pesticide? Whether one survives tasting Dipel says nothing about its safety. Eating is therefore simply a stunt. Moreover, if their professor truly thought this was a science experiment, then he needs reminding that experiments on human subjects require informed consent and ethics approval at the institutional level. However, no specific information about Dipel or its safety record was imparted to the audience. For instance, the professor could have, but did not, read out the official warnings on the label (of which more later).
The second issue concerns ethics. It is surely inappropriate for a professor ever to offer a pesticide to their students. Interactions between students and professors embody power imbalances that are considerable, some might say feudal. Students depend on their professors for grades and recommendations. Public seminars are a further pressure situation for students. The presence of senior departmental faculty at the seminar increases the pressure. Refusing the clear expectation of one faculty member in the presence of (loudly guffawing) others is not something that most students would do lightly. A professor’s invitation to eat a pesticide is therefore not likely to be perceived by students as a free choice.
Is Dipel ‘perfectly safe’?
It is hard to agree that Dipel and Dipel-type products are ‘very safe’.
In 1999 Bernstein et al. reported finding immune responses to Cry toxins in workers exposed to sprays of Dipel-type products (Bernstein et al., 1999). These researchers were investigating Dipel in the first place because:
“In 1992 the use of Bt (a Dipel-type spray) in an Asian gypsy moth control program was associated with classical allergic rhinitis symptoms, exacerbations of asthma, and skin reactions among exposed individuals reporting possible health effects after the spraying operation (2). Unfortunately, there was no follow-up…..Similar findings occurred during another Bt spraying in the spring of 1994 (8)”
As well, noted Bernstein and colleagues, rashes and oedema (swelling) were reported after a Dipel spray program in Oregon.
In subsequent research, Doekes et al concluded:
“Exposure to these microbial biopesticides may confer a risk of IgE-mediated sensitization.” (Doekes et al., 2004).
Such immune reactions were followed up by Barfod and colleagues, who researched Dipel-type products and found:
“low dose aerosol exposures to commercial Bt based biopesticides can induce sub-chronic lung inflammation in mice” (Barfod et al., 2010).
More recently still, Torres-Martınez et al. described one of the active ingredients of Dipel, the protein toxin Cry1Ac, in a paragraph that is worth quoting in full:
“Despite being regarded as innocuous to mammals, the Bt Cry1Ac toxin does interact with mammalian cells (Mesnage et al., 2013; Rubio-Infante and Moreno-Fierros, 2016). Cry1Ac protoxin is a potent immunogen (Moreno-Fierros et al., 2002, 2000; Vazquez-Padron et al., 1999), a mucosal adjuvant (Esquivel-Pérez and Moreno-Fierros, 2005; Vázquez et al., 1999) and can even function as a vaccine carrier (Moreno-Fierros et al., 2003). As an adjuvant, it enhanced protection in four murine infection models, specifically amoebic meningoencephalitis (Rojas-Hernández et al., 2004), malaria (Legorreta-Herrera et al., 2010), cysticercosis (Ibarra-Moreno et al., 2014) and brucellosis (González-González et al., 2015). When Cry1Ac protoxin was administered intranasally and intraperitoneally to mice, it increased the expression of the costimulatory molecules CD80 and CD86, the chemokine MCP-1, and the proinflammatory cytokines TNF-α and IL-6 in adherent cells from different mucosal sites.” (Torres-Martınez et al., 2016)
Their abstract concludes:
“the Cry1Ac toxin is not inert and has the ability to induce mucosal and systemic immunogenicity.”
As well as immune effects, Mezzomo and colleagues reported (like Mesnages et al. and Rubio-Infante and Moreno-Fierros before them) direct toxicity of Cry1Ac towards mammalian cells (Mezzomo, et al., 2013; Mesnage et al., 2013; Rubio-Infante and Moreno-Fierros, 2016). Mezzomo concluded:
“further studies are required to clarify the mechanism involved in the hematotoxicity found in mice, and to establish the toxicological risks to non-target organisms, especially mammals, before concluding that these microbiological control agents are safe for mammals.”
It should also be noted that bacterial spore preparations of the very closely related Bacillus thuringiensis var israelensis) can be lethal to mice (Thomas and Ellar, 1983).
In their short-term study these researchers found that, though the toxin appeared to be harmless by oral ingestion, when adult mice were injected all of them died within 12hrs, and suckling mice died within 3hrs.
Finally, the mode of action of Dipel, and Cry toxins in general, is to make holes in membranes. The toxin punctures cells causing them to swell and burst. Affected cells die directly; or, especially in the gut, following the entry of pathogens to the damaged cells (Latham et al., 2017).
The significance of this mechanism of action is that, in the case of Dipel, there can be no safety argument based on the claim that humans lack the target structure (the cell membrane) that Cry toxins are designed to destroy. Therefore, Dipel-type pesticides should be regarded as inherently hazardous. Indeed some researchers have found that, contrary to all industry claims, Cry1Ac does bind to mammal intestines (Vazquez-Padron et al., 2000).
To claim Dipel is ‘very safe’ ignores a great deal of scientific evidence.
Dipel, pesticides, and the law
The material safety data sheet (MSDS) that accompanies Dipel says:
“It is a violation of Federal law to use this product in a manner inconsistent with its FIFRA pesticide labeling.”
The MSDS also contains this statement about Prevention:
The MSDS further says:
“Avoid contact with skin and eyes…In case of contact with skin or eyes, rinse immediately and seek medical advice. Wear suitable protective clothing and eye/face protection.”
In other words, their professor broke the law. First, he broke it by consuming Dipel himself. Second, he broke it by inappropriately exposing the three students who did eat it. And thirdly, by failing to inform them of the necessary precautions once they were exposed.
The politics of pesticide eaters
The stunt of eating pesticides is not new. Entomologists as far back as the 1940s were filmed ‘demonstrating’ that DDT is “so-safe-you-can-eat-it“. Patrick Moore, the self-proclaimed Greenpeace founder turned glyphosate promoter has made a career claiming that drinking glyphosate was safe. At least until he was confronted with the opportunity to do so by a journalist at French TV station Canal+.
Whether they are scientists or not, and Kevin Folta is a horticulture professor, people who offer to taste pesticides are not doing science.
They are promoting corporate products. And, in fact, the Cornell professor was promoting a product too. The lecture “Biotechnology Is Helping Resource Poor Eggplant Farmers in Bangladesh–So why is GMWatch Against It?” describes a project he oversees for Cornell in Bangladesh.
Cornell and the Bangladesh government’s Agricultural Research Institute (BARI) have used a Monsanto transgene to develop a GMO brinjal (eggplant) variety that kills insects. The eggplant contains the Cry toxin, Cry1Ac. It is one of the toxins in Dipel, which explains the Dipel tasting.
The purpose of the GMO brinjal, depending on who you ask, is to defend the crop against a shoot-boring insect pest, or, it is to act as a trojan horse for GMO crops in Asia.
The project is controversial in other ways too. For one, because of an industry-funded 90-day rat feeding study that was examined by independent epidemiologist Lou Gallagher.
Gallagher wrote of the study:
“current results from these rat feeding studies indicate that rats eating Bt brinjal experienced organ and system damage: ovaries at half their normal weight, enlarged spleens with white blood cell counts at 35 to 40 percent higher than normal”
The effects on the rats are “consistent with hepatotoxicity” wrote Gallagher.
Secondly, some local observers believe the GMO Brinjal project is failing. A report from Bangladeshi NGO UBINIG states:
“A Deputy Agriculture Extension Officer (wishing to remain anonymous) said selected Deputy Agriculture Officers are given a target to give Bt brinjal seeds to one farmer only in three wards under a Union. Even that is difficult to find, because farmers do not want to take the seeds. A farmer given the seed once does not want to take it again, because the seeds do not grow well and do not give fruits. The plants are weak, and the fruits are not seen. On the other hand, farmers cultivating local varieties have good productivity and can earn good income. The officer was worried how to fulfill the target! It is very difficult to find farmers, but ‘we are helpless because we have to keep our job!’”
If the Bt Brinjal project is failing there is no mystery over the motivation for a sales pitch and perhaps no mystery either about why farmers, teachers, and government officials often feel so comfortable claiming that fracking fluids, plastic containers, toxic plumes, pesticides in food, lead in water, teflon pans, and the like are safe. They likely learned it in college.
Barfod, KK and SS Poulsen M Hammer and ST Larsen (2010) Sub-chronic lung inflammation after airway exposures to Bacillus thuringiensis biopesticides in mice. BMC Microbiology 10 :233.
Bernstein IL, Bernstein JA, Miller M, Tierzieva S, Bernstein DI, Lummus Z, et al (1999): Immune responses in farm workers after exposure to Bacillus thuringiensis pesticides. Environ. Health Perspect., 107:575-582.
Doekes G, Larsen P, Sigsgaard T and Baelum J (2004) IgE sensitization to bacterial and fungal biopesticides in a cohort of Danish greenhouse workers: The BIOGART Study. Am J Ind Med 46:404–407.
Latham J. R., Love M. & Hilbeck A. (2017) The distinct properties of natural and GM cry insecticidal proteins. Biotechnology and Genetic Engineering Reviews 33:1, 62-96, DOI: 10.1080/02648725.2017.1357295
McIntyre, L., Bernard, K., Beniac, D., Isaac-Renton, J. L., & Naseby, D. C. (2008). Identification of Bacillus cereus group species associated with food poisoning outbreaks in British Columbia, Canada. Applied and Environmental Microbiology, 74, 7451–7453. doi:10.1128/ AEM.01284-08
Mesnage R., E. Clair, S. Gress, C. Then, A. Székácsd and G.-E. Séralini (2013) Cytotoxicity on human cells of Cry1Ab and Cry1Ac Bt insecticidal toxins alone or with a glyphosate-based herbicide. J. Appl. Toxicol. 33: 695–699.
BP Mezzomo, AL Miranda-Vilela, I de Souza Freire, LCP Barbosa, FA Portilho, ZGM Lacava and CK Grisolia (2013) Hematotoxicity of Bacillus thuringiensis as Spore-crystal Strains Cry1Aa, Cry1Ab, Cry1Ac or Cry2Aa in Swiss Albino Mice. J Hematol Thromb Dis 1:1.
Moreno‐Fierros L, Garcia N, Gutiérrez R, Lopéz‐Revilla R and Vásquez‐Padrón RI (2000) Intranasal, rectal and intraperitoneal immunization with protoxin Cry1Ac from Bacillus thuringiensis induces compartmentalized serum. Microbes Infect. 2, 885–90.
Rubio-Infante, N., and Moreno-Fierros, L., 2016. An overview of the safety and biological effects of Bacillus thuringiensis Cry toxins in mammals. J. Appl. Toxicol. 36, 630–48. doi:10.1002/jat.3252
Thomas WE, Ellar DJ (1983) Bacillus thuringiensis var israelensis crystal deltaendotoxin: effects on insect and mammalian cells in vitro and in vivo. J Cell Sci 60: 181-197.
Torres-Martínez,M., N. Rubio-Infante A. L. García-Hernández R. Nava-Acosta, D. Ilhuicatzi-Alvarado L. Moreno-Fierros (2016) Cry1Ac toxin induces macrophage activation via ERK1/2, JNK and p38 mitogen-activated protein kinases. The International Journal of Biochemistry & Cell Biology 78: 106-115.
Vásquez‐Padrón RI, Gonzáles‐Cabrera J, Garcia‐Tovar C, Neri‐Bazan L, Lopéz‐Revilla R, Hernández M, Morena‐Fierra L and de la Riva GA (2000) Cry1Ac Protoxin from Bacillus thuringiensis sp. kurstaki HD73 binds to surface proteins in the mouse small intestine. Biochem and Biophys Research Comm 271:54‐58.
Vázquez-Padrón RI, Moreno-Fierros L, Neri-Bazán L, de la Riva GA, LópezRevilla R (1999) Intragastric and intraperitoneal administration of Cry1Ac protoxin from Bacillus thuringiensis induces systemic and mucosal antibody responses in mice. Life Sci 64: 1897-1912.
Vázquez, R.I., Moreno-Fierros, L., Neri-Bazán, L., De La Riva, G. a., LópezRevilla, R., 1999. Bacillus thuringiensis Cry1Ac protoxin is a potent systemic and mucosal adjuvant. Scand. J. Immunol. 49, 578–584.
If this article was useful to you please consider sharing it with your networks.