Let’s Talk About Pesticide Residues

By Anika Gatt Seretny, Senior Communications Manager at Croplife Europe.

This article was originally published on LinkedIn.

In a town normally buzzing with information and a steady stream of reports and policies being negotiated, I wanted to take advantage of the summer silence to reflect on some of the issues we are often asked about. To kick things off, I thought I’d focus on residues – a hot topic when it comes to chemicals – in my case, pesticides (obviously). A recent report by PAN Europe on pesticides residues got me thinking that sometimes the science and facts are getting lost.

First, so we are all on the same page, we must clarify what we mean by pesticide residues. Pesticide residues are traces of chemical or organic pesticides that may occur on, or in, the harvested crops. Can they be avoided? No. Farmers who comply with the (Good Agricultural Practice) principle of ‘using as little as possible and only when necessary’ can’t do more than they are already doing.

Trace ≠ Unsafe

This is where it gets complicated and where alarmist headlines confuse solid scientific concepts with health concerns.

Let’s start with what the science says. A fundamental scientific principle is that presence does not equal exposure to risk. In other words, pesticide residues on food do not automatically mean that the food is unsafe, or that you are being exposed to risk. Nevertheless, we see this misrepresentation of science in articles and reports about the residues found in food, soil, or even people’s urine. This false equivalence creates concern and uncertainty. What is often overlooked in the articles and reports is the concentration levels. And the possible risks associated with pesticide residues can only be discussed by taking into account concentration levels and the length of exposure.

Let’s break it down

A recent example of alarmist reporting said that ‘Residues on kiwi fruits rose from 4% in 2011 to 32% in 2019. This sounds scary, right? These numbers might make you think twice about buying and eating kiwis.

But let’s break it down. What this data means is that there was a rise in the number of controlled samples where the presence of pesticide residues was observed. It simply refers to the presence of residues, not their concentration levels, or the timescale during which people consumed the kiwis. In other words, although it is implied, the actual exposure to risk hasn’t necessarily risen at all.

When we talk about a possible risk, we need to introduce another element, called a Maximum Residue Level (MRL). Understandably, you may have not heard of it, but MRL is an extremely important limit that is calculated to introduce significant margins of safety that first ensure consumers are protected and second allow trade between countries. Once again, it’s not the mere presence of a residue that we need to look at – but rather an exceedance of an MRL which is the acceptable concentration level.

How is the MRL set and why is it used?

First, there are tests (performed before any pesticide can enter the market) that determine the NOAEL level – the No Observable Adverse Effect Level. This refers to the smallest amount of pesticide residue before an adverse reaction is observed. The NOAEL level is the first step to assessing a chemical’s safety. The NOAEL level is set with considerable conservatism. You can liken it to following a 120km speed limit on a motorway and keeping a 60m gap between each car. It’s the safety recommendation that gives you a near certainty of avoiding a collision on the road.

Based on this NOAEL, we then determine one very important element: the Acute Reference Dose, or ARfD.  This is a toxicological safety limit that specifies the amount of a substance which can be ingested on a single day without having any effect at all on the health of the consumer. And the way that the ARfD is calculated is by dividing the NOAEL by a factor of at least 100, so ensuring a huge margin of protection.

Going back to our motorway driving analogy, this would mean we apply a 6 kilometre safety gap between each car. Think of the traffic jams J. While these extreme safety measures are not put in place for cars, they are for food. And only when this 100x margin has been established is the Maximum Residue Level set, which is then hugely lower than the toxicological safety limits for every pesticide and crop combination.

This MRL number is a trading standard, or guideline, rather than a safety number and it is used to decide whether a crop can be traded or not. These are all important considerations that need to be understood when we read about pesticide residue levels in the media. Only by keeping all these elements in mind can we understand whether there is a health risk or not.

Let’s get back to kiwis

If you recall, the media headline was: Residues on kiwi fruits rose from 4% in 2011 to 32% in 2019. These percentages refer to how many cases were found where the MRL was exceeded – but they don’t mean that your exposure has risen by that much.

Let’s unpack this a bit more, based on what we have learned so far. We need to work backwards. Let’s apply the strictest MRL value there is 0.01 mg of residue per 1 kg of kiwis, and the strictest ARfD for kiwis: 0.06 mg/kg bodyweight. Using this figure, a person weighing 50kg would have to eat 300kg of kiwis a day to have a potential health safety risk – six times their body weight in a day!

This example demonstrates that only if the MRL is exceeded enormously could there be a possible human health concern.

It is also worth noting that the European Food Safety Authority provides an annual report that examines pesticide residue levels and their exceedance in foods on the European market. Since 2010 in the EU, on average 97% of food samples tested for pesticide residues are found to be within the legal limits (i.e. below the MRL value). This shows that pesticides are being applied correctly and safely in Europe.

Feed people, not fiction

Today, we have access to an unprecedented amount of data, while also having less and less time to understand what the data is actually telling us. While there is an obvious need for more education (I’m lucky to be advised by scientific experts in my organisation who help me understand what these levels mean), we need to contextualise the reports and data that are being presented into what this actually means in the real world. The public deserves to be given the facts, not just to be fed cherry-picked data that only tell part of the story.

To be sure, MRLs are not a very ‘sexy topic’, but they are certainly a hot one. There will always be battles over how to interpret the data, or over standards and levels.  But thinking in terms of concentration levels and remembering that presence does not mean risk will avoid some of the confusion.