Pesticide cocktails cause toxicity, even at doses allowed in the EU. New study

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Exposure to cocktails of pesticides and other agrotoxics, even at doses allowed in the EU, causes toxicity. And its effects can be measured, thanks to innovative survey techniques.
The study conducted by an international research team-including Fiorella Belpoggi, director of the Cancer Research Center at the Ramazzini Institute in Bologna-offers new perspectives in scientific risk assessment. (1)

Early comments from Professor Alberto Mantovani of the Istituto Superiore di Sanità (ISS).

Pesticide cocktail effect, the multiple exposure study

The study under review for the first time, compares the outcomes of ‘omics’ molecular analysis-the most advanced, in terms of levels of accuracy and detail-with those obtained through traditional procedures. Namely, the analytical methods still applied in the risk assessment required for pesticide authorization in the EU.

The overall goal of the research is to identify biochemical markers of toxicity before detecting disease in individuals exposed to mixes of pesticides and other agrotoxics. And indeed, omics molecular analysis proved capable of ‘seeing’ early signs of damage to the body related to exposure to the pesticide cocktail. The authors of the research therefore suggest adopting such standards in risk assessment procedures, in Europe entrusted to EFSA(European Food Safety Authority).

New frontiers for public health

‘Our data suggest that adoption of multi-omics as part of regulatory risk assessment procedures will result in more accurate outcome measures, with positive public health implications.’ (1)

The research is currently undergoing peer-review by experts in the field of study, awaiting publication in a scientific journal. Its full text is, moreover, already available on the BioRxiv preprint site. (1) Upon confirmation, it may make a major contribution to the analysis of risks related to the so-called cocktail effect (cumulative exposure to hazardous chemicals).

Residue testing of 6 widely used agrotoxics

The researchers replicated for 90 days on laboratory animals the conditions to which consumers of ‘conventional’ (i.e., non-organic) foods are subjected every day. That is, chronic exposure to a mix of the residues of 6 agrotoxics often detected in food: azoxystrobin, boscalid, chlorpyrifos, glyphosate, imidacloprid, and thiabendazole. Within the limits of the respectiveAcceptable Daily Intake (ADI).

The prevalence of these molecules in food is confirmed in the latest EFSA report on pesticide residues in food. (2) Where 2 or more molecules were found to be present in more than 1 in 4 samples (27.5 percent). And the 6 agrotoxics used in the study under review often appear there. Two of the poisons mentioned, for example, were even recently found in the pulp of non-organic bananas.

Acceptable results, applying traditional analysis standards

At first analysis, the guinea pigs showed no damage from exposure to the pesticide cocktail. Water and food consumption, as well as body weight, were similar in the control group and the group exposed to the agrotoxic mix. The latter showed only ‘A nonsignificant increase in the incidence of liver and kidney injury. A biochemical analysis of serum revealed only a small reduction in creatinine levels‘.

Risk analysis evaluated by traditional methods (blood analysis and histological examination of organs) employed both by industry and at the institutional level for pesticide approval, therefore, showed little or no physiological effects.

Worrying results, applying more advanced standards of analysis

In contrast, the use of more advanced standards of analysis-blood metabolomics, liver transcriptomics, and genome-wide DNA methylation analysis-reveals metabolic alterations in the gut and metabolome (the sum of metabolites), in the blood of guinea pigs, with effects on liver function.

Further research on in vitro bacterial cultures ‘also showed that the growth of Lactobacillus rhamnosus and Escherichia coliceppi were adversely affected by the mixture of pesticides at concentrations that were not inhibitory when exposure was to a single agent.’ (1)

The research continues

The results of the study show the inadequacy of toxicological risk assessments of molecules currently in use. Demonstrating the presence of biochemical changes related to exposure to pesticide mixes in doses so far deemed acceptable (at least 100 times lower than that showing no effect).

Further studies are essential to ascertain the true offensiveness of the detected alterations. We also need to identify the most dangerous synergies, since under different circumstances the pesticide in a mix produces toxic effects that are not detected in its exclusive use.

ISS Prof. Alberto Mantovani’s commentary.

Professor Alberto Mantovani is an internationally renowned toxicologist. Research director of the Istituto Superiore di Sanità (ISS), former president of the European Society of Teratology. As well as a longstanding member for 15 years of the Scientific Panel on Feed and Pesticides at EFSA(European Food Safety Authority), where he continues to work as an external expert. Mantovani had previously shared his thoughts on pesticides and the microbiome on this site. We have now gathered his initial comments on the study under review.

With the understanding that studies should be considered after they have passed peer-review, the idea of evaluating effects on the gut microbiome and liver transcriptomics and epigenetics is scientifically appealing. The intestines and liver are, in fact, the tissues that are sure to come in contact with residues in food.

Two problematic issues are the differences between the human and rodent gut microbiome, and especially the consequences of the effects found: simple response of the body to the foreign substances it ingests daily, or first steps toward the establishment of even serious adverse effects?

Pending discussion of the final version of the paper, it is undeniable that the study addresses a topical issue for risk assessment, namely the possible metabolic effects of multiple exposures to low levels of residues’.

Marta Strinati

Notes

(1) Robin Mesnage, Maxime Teixeira, Daniele Mandrioli, Laura Falcioni, Quinten Raymond Ducarmon, Romy Daniëlle Zwittink, Caroline Amiel, Jean-Michel Panoff, Emma Bourne, Emanuel Savage, Charles A Mein, Fiorella Belpoggi, Michael N Antoniou. Multi-omics phenotyping of the gut-liver axis allows health risk predictability from in vivo subchronic toxicity tests of a low-dose pesticide mixture. bioRxiv 2020.08.25.266528; doi: https://doi.org/10.1101/2020.08.25.266528

(2) EFSA (2019). The 2017 European Union report on pesticide residues in food. doi: https://doi.org/10.2903/j.efsa.2019.5743. At https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2019.5743

Marta Strinati

Professional journalist since January 1995, he has worked for newspapers (Il Messaggero, Paese Sera, La Stampa) and periodicals (NumeroUno, Il Salvagente). She is the author of journalistic surveys on food, she has published the book "Reading labels to know what we eat".