Pesticides: Why, how and what?

Pesticides:

Why, how and what?

BACKGROUND

ALS Laboratories (UK) Ltd (www. als-testi ng.co.uk) is one of the UK’s leading providers of food and drink testing services. With six accredited laboratories located across the country, they o er a comprehensive range of high quality, analytical testing services, including microbiological, nutritional, vitamins and minerals, pesticides and contaminants, allergens and speciation. They also provide clients with a wide range of consultancy services and technical support on food safety, labelling requirements, allergens management and sensory testing.

Is it a legal requirement, public safety or public perception? In this article, Buddhi Dias, ALS’s contaminants laboratory manager at their Chatteris site, considers the common reasons for testing food for pesticides, as well as what you should expect from a testing laboratory.

WHY DO WE NEED PESTICIDES?

If you ask your colleagues what is their perception of pesticides, what would be the top answers? Most likely the following will be at the top - poisonous, cancer causing, bee killers.

All of these have been in media headlines in one form or the other. As much as there is some truth for using those terms, we still rely heavily on use of pesticides. Global demand for food is ever increasing, with more and more of us changing our lifestyles and choices of food. According to UN Food and Agriculture Organisation data, half of all habitable land is used for agriculture.

Hence, to feed the ever-growing global populations, the yield of food production must be sustained and increased. The technology around farming is evolving to be able to give better yield, but the technology is not there yet to keep it sustainable and aff ordable. Hence, we still rely on old agricultural techniques, such as use of pesticides and crop rotation to increase and sustain crop yield. Pesticides are used for crop protection, to avoid diseases, unwanted vegetation, and pests. It is also used in the storage and transport of fresh produce.

One of the questions that is often asked by those working in the food industry is why do we still need pesticides? The answer is that pesticides are used to increase crop yield, keep costs down, and to protect and maintain the appearance of crops. Another reason which is not always immediately apparent is that pesticides are used to inhibit the production of natural plant toxins, such as glycoalkaloids, tropane alkaloids and pyrrolizidine alkaloids.

In 2019, there were two major foodpoisoning outbreaks in Uganda that resulted in fi ve deaths and hundreds of people being admitted to hospital (‘Tropane alkaloid contamination of agricultural commodities and food products in relation to consumer health: Learnings from the 2019 Uganda food aid outbreak’ – Abia – 2021 – Comprehensive Reviews in Food Science and Food Safety, Wiley Online Library).

Testing carried out revealed that the source of this poisoning was from a supercereal which contained tropane alkaloids. It has been suggested that without the use of pesticides the plants will create their own defensive mechanisms to combat pest and diseases, one such mechanism is plant toxins and these toxins can be far more dangerous than pesticides for human consumption, even in small doses. In summary, we still need pesticides to produce safe, quality food at aff ordable prices.

HOW DO WE MAKE IT SAFE?

We can all agree that pesticides are poisons, so how do we make sure that they are safe for use? The simple answer would be to adhere to maximum residue levels (MRLs).

When our clients ask for pesticide testing, many of them will request MRL testing as this is what is legislated, either, under EU regulations or as of January 2021 under GB regulations. These regulations are for any EU countries and Great Britain. It is slightly confusing, however, as there will be diff erent sets of MRLs for diff erent regions of the world. Other than MRLs set by diff erent countries/regions, there are internationally agreed MRLs under CODEX. Hence, it is always important to recognise where you are selling your product and if the product is legal to be sold under those regulations.

It is easy to think that MRLs, as well as the approval of an active substance,

that applies to Great Britain should be the same in Peru for example. However, it is not that straightforward as MRLs or approval of actives are set by data gathered by the pesticide producers. The data is gathered whilst doing field studies in different regions which can be determined by the weather and soli conditions, as well as many other factors. Therefore, a certain active could be approved for use in Peru and but not in GB. In some cases, the MRL would reflect this fact. This is where you have certain actives that are not approved for use but have higher set of MRLs.

To establish MRLs, several other factors are considered first. The first level that is established for an active is what is called the NOAEL, ‘No Observed Adverse Effect Level’. This is the highest level of pesticides that can be ingested without showing any adverse effects.

The next levels are what are used in consumer risk assessments, ADI and ARfD values, which are established by dividing the NOAEL by at least 100. ADI, Acceptable Daily Intake, is the safe amount of a pesticide that can be ingested every day over an entire lifetime without compromising the health of the consumer. ARfD, Acute Refence Dose, is the safe amount that can be ingested in a single day without effecting the health of the consumer, which, why these factors are used to calculate the risk factors of finding certain pesticides in products. This is a more beneficial tool when you are dealing with a mixture of commodities. MRLs are applied to the raw materials, so in order to establish the MRL of a product and grant approval for use, a dietary risk assessment is conducted using ARfD and ADI values. If the MRL values are safe under the worse-case scenarios, then the approval is granted and the MRL is established.

The MRLs are established as legal trade standards, intended to check if the pesticides have been applied correctly. Therefore, a minor MRL exceedance does not automatically pose a risk to the consumer. It is then pertinent to question why the industry like to see residue levels that are 50% or 30% below the MRL. What is the purpose of these limits if there are already established safe limits to the consumer?

WHAT TO EXPECT FROM A LABORATORY

One of the key factors in deciding your testing partner, apart from their capabilities, is whether the lab is accredited or not. The fundamental basis on which all the accreditations are carried out is by assessing against the ISO 17025 standards. These standards are set to harmonise all labs across the world. In the UK the accreditation and assessments are carried out by UKAS. Each country will have its own accreditation body to verify if a lab is carrying out testing according to the ISO standards. Within the European Union, there is an extra guidance document for pesticide testing laboratories to follow. SANTE/12682/2019, a complimentary document to ISO 17025 guidelines, helps to provide harmonised, accurate testing methods for labs, as well as ensuring the quality and the comparability of results across different labs. It is not yet clear if GB will adopt this or will provide its own set of testing guidelines. It is difficult to see the latter happening as SANTE is already a well-established set of guidelines. SANTE document have guidance from sample preparation, extraction, calibration, instrument calibration, confirmation of results to commodity groups. SANTE guidelines also provides a default measurement of uncertainty (MU) for detected pesticides as ±50%. To use this value by a laboratory, they must demonstrate that its own expanded MU is below 50%. This value is also recommended to use by regulatory authorities when they are enforcing MRL exceedances.

Most, if not all labs, will be using the well-established QuEChERs method for pesticide extraction, whether it is the EN method or the AOAC method. Either way they all have the sample principle. This method has revolutionised how pesticides have been tested. Prior to this, individual sample types had individual testing methods and used high toxicity solvents in larger volumes. Also, the number of actives previously screened was far less than what currently screened for. With the introduction of QuEChERs, it allows for extraction of multiple different sample types using one extraction and using safer solvents in smaller quantities, which allows for a safer and cheaper extraction.

Before the extraction can take place, samples are homogenised down to either a fine powder or a smooth paste. It is important that representative samples are submitted to the lab and the minimum weight guidelines are followed according to 2002/63/EC. In the lab, it is also important to take the correct portion where MRL is applicable to and take a representative portion to be homogenised. These steps are vital in getting accurate results when using QuEChERs method.

Essentially QuEChERs can be broken down to two steps. One is extraction and the next is clean up. During the extraction step, the pesticides are removed from the sample into an extract solvent. Then during the second step, many different interferences are removed. This is then ready to be run on chromatographic systems. Depending on the sample type the clean up can vary to aid the process. For more complex matrix such as teas and spices, a more extensive clean-up process is carried out compared to fruit or vegetables.

The rate determining steps of the process, in terms of releasing results, is the run time on the different chromatographic systems. In pesticides analysis, gas chromatography (GC) and liquid chromatography (LC), coupled with a mass spectrometry (MS) are utilised to give quantitate results. A typical runtime for a sample on an LC system can be somewhere between 12-15 minutes. Whereas on a GC system it is around 30 minutes. Hence, a lab is limited on how many samples can be done by the number of GC systems they possess. Similarly, this will also limit how many same day samples can be reported.

Once all the QC criteria has passed and any MRL exceedances are confirmed by means of repeat analysis, the lab is ready to report the results to the client. If there is an MRL exceedance, it is always good to check with the lab if a repeat analysis has been done and even better to send in a second potion from the batch to test, before any red buttons are hit (ALS has been conducting pesticide testing for over 30 years and we have seen a wide variety of samples and requests).