Deconstructing a BLT using pesticides.

In this latest in a series of advisory articles from ALS, Buddhi Dias - the company’s contaminants and pesticides laboratory manager, who heads their Contaminants and Pesticides Department to provide reliable testing, technical advice and training days – considers the rationale behind testing for pesticide residues in a sandwich product.

BACKGROUND

ALS Laboratories (UK) Ltd (www.als-testing.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 offer 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.

DETECTION

Because maximum residue levels (MRL) are applied to raw materials, the question of testing the final product for pesticides has been always debated.

A frequently asked question is “what are the benefits of testing the final product for pesticides if there are no MRLs to compare the results against, and if we are to test a final product such as a sandwich, how could we make the results we find meaningful?”

For the purpose of this article, we carried out a multi-residue screen on a supermarket bought BLT sandwich. The testing performed was a routine screen that we carry out daily, which covers 500 different pesticides. This process involves homogenising the sample and taking a portion to be extracted using QuEChER’s technique. Once the sample is extracted, a portion of this is then run on a liquid chromatography (LC) and gas chromatography (GC) system, coupled with mass spectrometry (MS) to give us qualitative results.

LC and GC systems are acting to separate out different pesticides, a bit like when you put an ink dot on paper and let the colours separate out, during the school science lessons. The MS system will then detect and identify the different pesticides.

The pesticides that were detected above the 0.01mg/kg reporting limit (RL) on this sandwich were deltamethrin and piperonyl butoxide. The latter is not classed as a pesticide and there are no set MRLs for any raw material for this. Piperonyl butoxide is what known as a synergist. This is a part of the formulation of a pesticide makeup. It helps the pesticides to penetrate more easily to the plant and is commonly used with the pyrethroids class of pesticides. Apart from these, three other pesticides were detected well below the RL. These were boscalid, tebuconazole and pendimethalin. The reporting limit is also known as the limit of quantitation (LOQ). This is the limit at or above which a result can be accurately quantitated, and a value can be given. Below this limit, pesticides can be detected up until the limit of detection (LOD), however the values that are calculated would be qualitative only.

SAFE?

Now we have information regarding the pesticides that can be found in a sandwich, how can we say this is safe or it doesn’t breach any MRLs? One approach could be looking at using a consumer risk assessment model to

calculate the risk of eating the amount of pesticides that was found. This can be calculated for long term (chronic) or short term (acute) risk.

The acute risk assessment utilises the acceptable daily intake (ADI) of a pesticide. This is the safe amount of pesticide that can be ingested throughout a person’s life span. Whereas chronic risk assessment will utilise the acute reference dose (ARfD) of a pesticide, which is the amount of pesticides that can be ingested over a 24hour period without a health risk. These calculations will also utilise the amount of the product consumed as well as the body weight of the person consuming. Usually, calculations are done on worst case scenario. The calculated result is given as a percentage, and the higher the percentage the more risk it causes to the consumer.

Another approach could be to look at what raw materials used in the sandwich could contain these pesticides and check if the MRLs for those raw materials are adhered to. For this case, bacon was not analysed. Typically, the only pesticides found in meat are the fat soluble compounds such as aldrin, DDT and hexachlorobenzene (HCB). These compounds are no longer used but can persist in the environment and hence enter the food chain. A typical MRL for meat for DDT is 1 mg/kg.

RESULTS

Results for samples that were analysed at ALS, between October 2020 to October 2021, for lettuce, tomatoes and wheat were looked at. Figures one to three show the top six pesticides detected for each commodity. Table 1 indicates the GB MRLs for each pesticide found with respect to each commodity.

When we compare these charts, we can assume that the deltamethrin that was found in the BLT sandwich is most likely come from the bread portion. Thus, we can compare the levels found against the wheat MRL to see if it possesses an issue. In this scenario the levels found were at 0.02mg/kg and the MRL is at 1mg/kg. Similarly, even though there are no MRLs for piperonyl butoxide, we can again associate the origin of this to the bread portion.

If we look at the pesticides that were detected below the reporting limit, tebuconazole would most likely be from the bread portion as it is the most common pesticide that was found in samples of wheat that were tested at ALS. Boscalid and pendimethalin can be associated with the lettuce portion of the sandwich.

CONCLUSION

It was surprising to not find both of the top pesticides found for tomatoes and lettuce in the sandwich. This could be down to the variation in pesticides we see, as pesticides do not get applied evenly and different portions of the fruit or the leaf could have different levels. Hence, if we analyse another sandwich, we may get slightly different results. One of the reasons for the ±50% uncertainty on pesticide results is due to this variation. Also, most of the sandwich is the bread portion and only small percentage is lettuce. Hence, the residue could be diluted out in the final product.

The answer to the question, “what is the benefit of analysing a final product such as a BLT sandwich for pesticides?” lies in the purpose of the testing. It is always important to ask yourself why we are carrying out testing and what information are you looking to gain? It is always beneficial to test the raw material, however if the final product is tested and residues are found, then their significance can be assessed according to the forementioned techniques.

45%

30%

18%

13% 11%

9%

Piperonyl Butoxide Pirimiphos-methyl Tebuconazole Deltamethrin Chlormequat Glyphosate

Difenoconazole Azoxystrobin Fludioxonil Cyprodinil Fluopyram Imidacloprid

Cyprodinil Boscalid Acetamiprid Fludioxonil Pendimethalin Azoxystrobin

20%

17% 17%

15%

10% 10%

26%

18%

14% 14%

11%

9%

TABLE 1

Acetamiprid Azoxystrobin Boscalid Chlormequat Cyprodinil Deltamethrin Difenoconazole Fludioxonil Fluopyram Glyphosate Imidacloprid Pendimethalin Piperonyl Butoxide Pirimiphos-methyl Tebuconazole

Lettuce Tomatoes Wheat

1.5 15 50 0.01 15 0.5 4 40 15 0.1 2 4 n/a 0.01 0.5 0.5 3 3 0.01 1.5 0.07 2 3 0.9 0.1 0.5 0.05 n/a 0.01 0.9 0.1 0.5 0.8 7 0.5 1 0.1 0.01 0.9 10 0.1 0.05 n/a 5 0.3