A study on edible oils from Italy and Spain reveals the presence of microplastics (MPs) in olive oil, including extra virgin olive oil, sunflower oil, and mixed seed oils.
Olive oil producers
Almost 67% of the world’s olive oil production is grown in the EU, where Mediterranean countries lead the ranking for this production.
In the EU, around 4 million hectares are cultivated using different production techniques, from the most traditional and ecological to the most intensive.
Among the largest consumers of olive oil are Spain and Italy, with an approximate consumption of 500,000 tons per year each.
Investigate for the first time the presence of microplastics in different edible vegetable oils
This study, published on the platform ScienceDirect, aimed to investigate for the first time the presence of MPs in different edible vegetable oils. Both in extra virgin olive oil (EVOO) and olive oil and other types of edible oils, such as sunflower oil and mixed seed oil. The study analyzed the presence of MPs in oils packaged in PET and glass bottles, produced in Italy and Spain.
It should be noted that another recent study conducted in the US has already identified the presence of MPs in edible oils, such as rapeseed, olive, coconut, and sunflower oils, packaged in polyethylene terephthalate (PET) bottles, all of which originated in the US.
The researchers analyzed a total of nine samples of edible vegetable oil. These were purchased in regular stores, six of them in Valencia (Spain) and three in Bologna (Italy).
List of vegetable oil samples analyzed in this study, with the type of material used for both the container and the cap.
“The oil samples had different compositions, such as EVOO, olive oil, sunflower oil, and mixed seed oil. Most of them (seven samples) were packaged in PET bottles with low-density polyethylene (LDPE) or high-density polyethylene (HDPE) caps, and the others (two samples) were packaged in glass bottles with LDPE caps.»
Analytical methodology
The general analytical procedure can be seen in the image below. The samples were first shaken in an orbital mixer for a limited time and then each sample was diluted with a mixture of ethanol and hexane.
The diluted samples were filtered to extract the MPs and analyzed using infrared microscopy (μ-FTIR).
Diagram of the general analytical procedure.
Throughout the analytical stage, strict hygienic conditions were maintained to prevent any type of contamination by PMs from the material used during the investigation. Even the lab coats used during the tests were taken into account, and filtering equipment was used to eliminate airborne MPs.
“For each oil sample, a triplicate analysis was performed to obtain a statistical overview of the abundance of MPs and the characteristics of the particles per homogenized sample.”
Study conclusions
This study demonstrates that commercial edible vegetable oils from Italy and Spain (including EVOO, olive oil, sunflower oil, and mixed seed oil) contain varying amounts of MPs in their composition.
The analyses detected and characterized six different polymers: polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene-polypropylene copolymer (PE-PP), polyamide (PA), and polytetrafluoroethylene (PTFE), commonly known as Teflon.
“To identify MPs, the acquired spectra were automatically compared with reference polymer libraries.”
The study shows that edible vegetable oils contain varying amounts of MPs in their composition.
The most abundant microplastics
The most abundant MPs were those composed of PE (50.3%), widely used in bottle caps, and PP (28.7%), used for food packaging that requires high resistance or in the manufacture of water pipes.
The study itself indicates that “LDPE particles, like HDPE particles, were classified as PE in this study, as they have very similar spectra in μ-FTIR analysis.”
Other materials identified were PA (7.7%), PE-PP (6.3%), PTFE (4.2%), and PET (2.8%).
Total number of MPs identified by polymer composition in the samples analyzed.
Number of particles per liter (NMPs/L) and polymer composition obtained in the analysis of oil samples.
INTERVIEW WITH Dr. Pablo Miralles Ibarra
- 1. For obvious reasons, the study does not reveal the brands analyzed. Were there any differences in the results based on the quality of the oil or the “prestige” of the brand?
- 2. Did the analysis take into account the method of olive production, depending on whether it was organically grown, super-intensive, etc.?
- 3. The study indicates that PE, present in the composition of the caps, was not found in all samples. Why might this be?
- 4. It is striking that PET, the base material from which the bottles are made, only appears in 4 of the 7 samples analyzed. Could this have something to do with differences in packaging times? What could be the reason for this?
- 5. PP does appear in all the samples analyzed, and in one of the glass containers it stands out above the other polymer detected. What could be the explanation for this?
- 6. There are no data on MPs found in sizes smaller than 20 µm. With the data obtained in the study, could an estimate be made of how many of these particles could be released in the samples?
- 7. How do you think the processes of cultivation, harvesting, transport, processing, etc. can influence the release of MPs into oils? Could this explain the presence of PP, PTFE (Teflon), and PA in the samples?
- 8. Based on the results obtained, do you think it would be interesting to further investigate and take into account factors such as the type of crop and subsequent treatments?
Dr. Pablo Miralles Ibarra
Postdoctoral researcher in the Food Safety Research Area at FISABIO-Public Health. Dr. in Chemistry from the University of Valencia, Spain (2019). He developed a thesis on analytical methods applied to the safety assessment of cosmetic products. His current research focuses on the study of emerging contaminants and substances of interest in food, environmental, and biological matrices, using advanced analytical techniques such as high-resolution mass spectrometry. He has participated in various competitive research projects, has more than 25 scientific publications, and has been a reviewer and guest editor for several international journals. He is a member of the Royal Spanish Society of Chemistry, the Spanish Society of Analytical Chemistry, and various European scientific networks. Since 2023, he has been a guest expert on the Interministerial Commission for Human Biomonitoring (CIBMH), coordinated by the Ministry of Health and the Carlos III Health Institute.
1. For obvious reasons, the study does not reveal the brands analyzed. Were there any differences in the results based on the quality of the oil or the “prestige” of the brand?
In this study, microplastics were found in all oil samples analyzed, but no significant differences were observed in their abundance based on oil quality or type of packaging. However, further studies involving a larger number of samples would be necessary to draw broader conclusions.
2. Did the analysis take into account the method of olive production, depending on whether it was organically grown, super-intensive, etc.?
The study did not include information on the method of cultivation of the olives, as this was not available on all the labels of the samples purchased, and other types of oil, such as sunflower and other seeds, were also studied. It is known that agricultural practices, such as the use of plastic mulch, influence MP contamination in the environment, so the method of cultivation could be a relevant factor.
3. The study indicates that PE, present in the composition of the caps, was not found in all samples. Why might this be?
Although PE is a common material in caps, its presence in the form of microplastics may depend on multiple factors: contact time with the oil, storage conditions, temperature, etc. The absence of PE microplastics in one of the samples may be due to lower migration from the cap, or even differences in the design of the closure.
4. It is striking that PET, the base material from which the bottles are made, only appears in 4 of the 7 samples analyzed. Could this have something to do with differences in packaging times? What could be the reason for this?
As in the case of caps, the time elapsed between packaging and analysis, as well as other factors such as storage temperature or handling of the containers, may influence the release of microplastics. The absence of PET in the glass-packaged samples reinforces the hypothesis that this polymer comes directly from the container.
5. PP does appear in all the samples analyzed, and in one of the glass containers it stands out above the other polymer detected. What could be the explanation for this?
The widespread presence of PP can be explained by its extensive use in the food industry, from components in filtration systems or pipes to processing machinery parts. Its detection in a glass-packaged sample suggests that it does not come directly from the packaging, but from earlier stages in the production chain.
6. There are no data on MPs found in sizes smaller than 20 µm. With the data obtained in the study, could an estimate be made of how many of these particles could be released in the samples?
The methodology used (μ-FTIR) has a detection limit close to 20 µm, so particles below that size were not identified, although their presence cannot be ruled out. Estimating the amount of smaller particles would require the use of complementary techniques, such as Raman spectroscopy. This aspect represents a key line of future research, given the possible toxicological impact associated with smaller particles. In general, it is estimated that the abundance of microplastics tends to increase as their size decreases.
7. How do you think the processes of cultivation, harvesting, transport, processing, etc. can influence the release of MPs into oils? Could this explain the presence of PP, PTFE (Teflon), and PA in the samples?
The oil production processes, from cultivation, harvesting, processing, packaging, and storage, can be significant sources of microplastic contamination. The different plastic materials used in filtration systems, pipes, pumping equipment, and agricultural machinery, among others, can release particles during any of these stages.
8. Based on the results obtained, do you think it would be interesting to further investigate and take into account factors such as the type of crop and subsequent treatments?
Without a doubt, this study opens up a promising line of research. Including other factors such as crop type, harvesting systems, or subsequent treatments would allow for a better assessment of the primary sources of microplastics in oil. This would help establish preventive measures throughout the entire production chain. Furthermore, these findings require additional studies to clarify not only the origin of the particles but also the possible health risks to consumers.