Glyphosate cancer confusion

7 Dec 2015

In my mid-April blog, “Roundup causing cancer?”, the classification of glyphosate by the International Agency for Research on Cancer (IARC - part of the World Health Organisation) as a probable carcinogen was discussed. Its evidence in humans was from correlating the occurrence of non-Hodgkin lymphoma with exposure to formulated glyphosate products, mostly agricultural, in the USA, Canada and Sweden. The concern about such studies is that there are no controls which allow for the exclusion of the many other farming practices which may have been causative. Recently, the European Food Standards Agency (EFSA) has concluded that “glyphosate is unlikely to pose a carcinogenic hazard to humans and the evidence does not support classification with regard to its carcinogenic potential”.

So why is there a difference of opinion between these two august bodies? Looking at the statements made by people far brighter than me, it seems that there are more reasons than the few I am about to mention.

Firstly, IARC, wholly or partly, inevitably based its opinion on studies of the product whilst EFSA based its opinion on just the active substance. When Roundup was first introduced I was led to understand that the acute toxicity (symptoms within 24 hours) of the formulants was higher than the glyphosate itself but the product was still very safe. The Soil Association raised the issue of the risk from the formulants even before the publication of the EFSA opinion. In the European Union context, the European Commission (EC) approves the active substance (in this case glyphosate) and individual zones or member states authorise the formulated products that can only contain EC approved active substances. I find it comforting that there are some very precautionary inclined EU member states that have authorised formulated products based on glyphosate.

IARC admitted that its opinion was based on a small database of scientific evidence and EFSA was able to assess a larger database. It also seems that IARC re-analysed some of the data in the papers it considered. The reasons for this are unclear and the authors of those papers may or may not have agreed with the method of analysis carried out by IARC.

There also appears to be a different approach between the two organisations when coming to their conclusions. According to the genotoxicologist Dr Peter Jenkinson, “EFSA followed a weight of evidence approach whereas IARC took the view that if one study showed a positive result then it took precedence over negative studies, even though there may be many more negative than positive studies.”

These two opinions were about assessing the hazard posed by glyphosate. Just to remind you, electricity is hazardous but the risk of electrocution is acceptable. This is because risk is a combination of hazard and exposure. As always with the risk from chemicals, it is about the dose. For instance, formaldehyde is listed by IARC as a Group 1 carcinogen (its highest risk category meaning that it will definitely cause cancer). No pesticides appear to feature in this category but some medicines do. Formaldehyde naturally occurs in apples at concentrations of up to 22 parts per million (ppm) but at this concentration does not appear to be a risk. The maximum residue limit (MRL) for glyphosate in cereal grains is currently 30 ppm but this may change because its EC re-approval is currently being considered. I must emphasise that a MRL is not a value above which there is harm to health but is the highest level of a pesticide residue that is legally tolerated in or on food or feed when pesticides are applied correctly (Good Agricultural Practice).

There has been much fun made of IARC in terms of its opinion that red meat is probably carcinogenic and processed

meat is carcinogenic. The statistic quoted on the TV programme Have I Got News For You was that IARC has examined 941 substances and has only found one to be non-carcinogenic. This may be a little unfair because much of their

work may have been directed at substances where there was a real or perceived suspicion (there is no shortage of accusations from ‘green’ groups about glyphosate!). Many things when taken to excess are hazardous but in real life do not pose an unacceptable risk. It does not help I

ARC that the World Health Organisation has been widely criticised over recent weeks, notably for its slow response to the Ebola outbreak in Africa.

So my conclusion is very much the same as my previous blog. Glyphosate products are safe when used a directed.