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Proposed Increase To Glyphosate Limits – Expert Reaction
NZ Food Safety has proposed changing the residue limits allowed in food for several agricultural compounds.
The proposed amendments change or set maximum residue levels in food sold in NZ for 14 substances, including glyphosate (used in Roundup herbicide).
Glyphosate limits would increase for certain cereal and pea crops, to “support existing use” as a preharvest herbicide or dessicant. Submissions on the proposal closed on Friday, and the proposed amendments may progress, be modified, or be withdrawn.
The Science Media Centre asked experts to comment.
Associate Professor Melanie Kah, School of Environment, University of Auckland, comments:
“NZ Food Safety recently proposed to amend the Maximum Residue Limit for a dozen pesticides. The one for glyphosate raised concerns probably because glyphosate is often taken as an example for toxic pesticides by the public, even though it is a substance with a relatively low toxicity compared to other pesticides.
“The Maximum Residue Limit for glyphosate is proposed to be raised from a default value (0.1 mg/kg) to 10 mg/kg, which is similar or lower compared to Australian and international limits. The change is proposed to reflect potential residues resulting from current uses of glyphosate as pre-harvest desiccant following Good Agricultural Practices (i.e. how the product should be used following label instructions). It does not mean farmers will aim to have that level on produce. Surveys generally indicate that levels of residues are lower than that.
“Rather than focusing on the Maximum Residue Limit value and glyphosate in particular, I would question the practice of using herbicides as pre-harvest desiccant to facilitate harvest, which is a practice that is banned in other parts of the world e.g. Europe, mainly due to concerns related to residues on grains and impact on environmental health.”
No conflicts of interest.
Professor John D. Potter, Centre for Public Health Research, Massey University, comments:
“Glyphosate is a herbicide that now accounts for about 25% of the world’s biocide use.
“Glyphosate was identified in 2015 as a probable human carcinogen by the International Agency for Research on Cancer, the cancer research arm of WHO. It has since been shown, in animal experiments, to also cause changes in intestinal microbes and the structure and permeability (increasing leakiness) of the wall of the intestine as well as altering lipid metabolism.
“Further, as it disrupts these microbes, it is probably altering the structure, function, and balance of those that live in the soil, with knock-on effects on soil quality, crop-raising, etc. It has now been banned and restricted in many countries.
“It is widespread in food and in human blood worldwide. As a consequence, it is difficult to establish the full range of impacts on human health because there are almost no unexposed people to compare with those who are exposed.
“What is clear is that as “acceptable” levels rise, spraying will result in increased exposure for those who apply this herbicide for a living and for those who live downwind from sprayed crops.
“The Precautionary Principle would suggest that it is up to glyphosate’s advocates to prove its safety and, in the absence of such proof, to reduce or eliminate exposure.
“At the very least, Aotearoa’s government can be asked why they would choose now, in face of the evidence, to reduce restrictions.”
No conflicts of interest.
Professor of Toxicology Ian Shaw, School of Physical & Chemical Sciences, University of Canterbury, comments:
“The government is proposing an increase in the Maximum Residue Level for the herbicide glyphosate (the active ingredient in Roundup) from the default level of 0.1 mg/kg to 10.0 mg/kg.
“Pesticide Maximum Residue Levels are determined by measuring the concentration in a crop that was treated with the pesticide under Good Agricultural Practice. Maximum Residue Levels are trading standards, not consumer safety measures.
“The Acceptable Daily Intake is a consumer safety standard. Estimating glyphosate intake at the proposed new MRL (for example in wheat) shows that the proposed limit is of little or no toxicological concern. For glyphosate, the Acceptable Daily Intake is based on long term effects in rats.
“The government is also revising the genetically modified organism legislation. This might result in the approval of GM glyphosate resistant (Roundup Ready) crops in New Zealand.
“The use of glyphosate on Roundup Ready crops means higher crop residues, which would necessitate a higher Maximum Residue Level to facilitate trade. The cynic in me wonders if the two proposed legislative changes are linked.”
No conflicts of interest.
Science Media Centre NZ
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