Why is it possible that glyphosate in environmental concentrations affects animals?

Keskiviikko 22.4.2020 klo 16:18 - Mikko Nikinmaa

Glyphosate was taken to be a very good herbicide, because it disturbs the function of shikimic acid pathway via an inhibition of the enzyme 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase. This pathway is unique to plants and some micro-organisms. Thus, the toxicity of glyphosate to animals is expected to be low. Indeed, most studies on animal cells and also laboratory animals showed quite low toxicity of glyphosate to animals. Thus, for a long time it has been thought that the compound can be used without any worries about effects to animals at the concentrations needed for controlling weeds. The compound is quite stable with an estimated half-life of up to 200 days in soil. This means that yearly application increases its level through the years. In water the half-life appears to be somewhat shorter, about 3 months.

However, information about effects on animals started accumulating. This led to strong polarization between proponents and opponents of glyphosate use. If one examines the question based on scientific grounds, this should not be the case. Roundup.jpgOne should try to resolve the two opposite findings: little toxicity in controlled laboratory experiments, especially on animal cells, and effects on animals, especially in field experiments. It should be pointed out here that the reported effects on animals, e.g. the compound causing cancer, have used very high environmentally non-relevant concentrations. Thus, I find the Californian court decision that Bayer-Monsato should pay a multi-million dollar sum to plaintiffs for causing their cancer somewhat surprising.

The question really boils down to the effects of glyphosate on the microbiota of animals, and the importance of microbiota and its changes on the well-being and function of animals. It is clear that environmental concentrations of glyphosate can affect some microbes. It is also clear that the compound is taken up by animals, so regardless of their location in the animal body, the micro-organisms will be exposed to glyphosate. Studies about the importance of microbiota on animal functions are still in their infancy., but already even interactions between microbiota and neural functions have been described: gut microbes can affect sleep quality and depression. The direct effects of glyphosate on the microbiota of animals can thus affect animal functions indirectly.

In addition to the effects of glyphosate itself on the microbiota, the commercial formulations of glyphosate contain additives. The additives are trade secrets, but it appears that they can be much more acutely toxic to animals than the major active compound. However, since their structure is not known, proper toxicity evaluations by independent scientists are impossible.

 

Kommentoi kirjoitusta. Avainsanat: herbicide, weed conrol, non-target organism

Microbiota and environmental pollution

Sunnuntai 26.11.2017 klo 17:40 - Mikko Nikinmaa

All animals contain microbes, often billions of them.The symbiosis between the host and its microbes is essential for the well-being of the animal. Two examples of this show how important it is. If one is eating antibiotics, the gut microflora becomes disturbed, and, e.g., diarrhea can be the result. Ruminants utilize bacteria for digesting grass. Because of the fact that microbes are affected by completely different toxins than their animal hosts, surprising effects of environmental pollutants can be observed. For example, some herbicides may affect the necessary microbes of man, and because of this, although the effective compound does not exert any toxicity on the animal itself, by disturbing the microbial community of the animal, it may influence its well being. Effects of environmental pollution on the microbiota of animals is so far poorly studied - and is undoubtedly one area, which will receive important attention in the future.

Kommentoi kirjoitusta. Avainsanat: contaminants, non-target organisms, synergism

Poorly known addditives may be more harmful than glyphosate itself

Torstai 22.6.2017 klo 10:31 - Mikko Nikinmaa

With the discussion about the harmful effects of glyphosate on tends to forget that the additives in the different commercial formulations may be more harmful to non-target species than the main toxic ingredient. It is undoubtedly true that the persistence of glyphosate in soil in different climatic zones is poorly known, and because of the antibiotic properties of the compound, knowing this would be necessary to be able to estimate the effects of the toxin on the community functions of soil micro-organisms.

However, for animals the additives in the commercial formulations are the real problem. The additives are a commercial secrecy, but an example of their importance in mediating at least acute toxic effects in non-target animals comes from a recent study: pure glyphosate and one commercial formulation showed negligible toxic effects, whereas another formulation was acutely highly toxic. Since the additives are a secrecy, the properties of the compounds used cannot be studied, since the compounds in question are not known.

Two things should generally be noted about glyphosate and its formulations. First: because glyphosate is affecting pathways specific to autotrophic organisms, it has not been considered important that the effects of its commercial formulations are studied with non-target animals. And because the additives are a secrecy, even if the effects on non-target animals are studied, one does not know the toxic compound. Second: the chronic effects of the main toxic ingredient and additives have not been investigated at all on non-target animals. Because of this, there are wild, and completely unsubstantiated, rumours about the harmful effects caused.

Kommentoi kirjoitusta. Avainsanat: pesticides, environmenal pollution, non-target organisms