A potential foreign material concern for millers.
Introduction to Microplastics
Cleaning a clothes dryer lint screen drew my thoughts toward the issues of micro and nanoplastics that have been reported and discussed with greater frequency in recent years.
Early reporting focused on contamination of water and species living in and around water. Coverage has increasingly expanded to concerns with micro and nanoplastics in the human food chain and impact on humans. Millers are proactive in seeking out food-grade materials for use in our milling processes especially where potential food contact may occur. The purpose of this article is to present background regarding micro and nanoplastics as a potential foreign material concern for millers.
The term “microplastics” was not formally used until 2004; however, shortly after the widespread use of plastics in 1950, microplastics first appeared in aquatic life and have been confirmed to exist in many common day food products, as well as within organs of the human body, including the brain, testicles, heart, stomach, lymph nodes, and placenta. Furthermore, microplastics pass through the human body in urine, breastmilk, semen, and meconium (an infant’s first stool).
Size definitions of plastic environmental pollutants are not universally defined (see the table on p. 7). Macroplastics from 5mm to 10cm are highly visible and can be seen with the naked eye. Such relatively large materials would be removed by re-bolt or control sifters in flour milling operations and typically observed in other grain products for human or animal food production. If observed in food products, they likely would be considered a choking hazard and potentially injurious to human health.
Microplastic size defined by some include particles from 5mm down to 1mm with the range from 5mm down to 1mm considered large microplastics. Large microplastics are highly visible in most grain flour and grain products. Microplastics between 1mm (1,000 µm) and 20 µm would be considered small microplastics. Flour produced through a 150 µm screen in a flour mill could therefore contain both micro and nanoplastics from the environment. Depending on size and color, such particles may be identifiable but not easily removed.
Of course, nanoplastics of less than 1 µm would no longer be visible and only detectable with significant effort and impossible to remove from either the environment or food product. Some microplastics in the environment are direct components of paints, cleaners, and health and beauty products, such as toothpaste.
The release of microplastics into the environment is estimated to nearly double to 20-80 million metric tons per year by 2040. It is estimated that adults take in the equivalent of one credit card worth of microplastics per week.
Plastics break down by weathering in the environment over time into smaller and smaller particles. There is evidence that bacteria, fungi, and/or enzymes they produce can also break down synthetic plastics. It is not known if or when biological management or control of micro or nanoplastics will be a significantly meaningful control method.
It is known, however, that incineration of plastics as a method of control is not a suitable due to release of various chemicals into the atmosphere. Flour milling utilizes approximately 100-138 cubic feet of air per pound of flour produced. Particulate pollution (also known as particulate matter, including PM 2.5 and PM 10) is one of the five factors the U.S. Environmental Protection Agency (EPA) uses to assess air quality and may be retained in mill product and co-product.
This type of contamination is beyond the miller’s control. Millers are encouraged, however, to manage the use of plastic materials meeting food grade requirements with maximum wear resistance and replace damaged or worn component in our milling processes.
Impact of Micro and Nanoplastics
The impact of micro and nanoplastics on human health is not well known; however, studies in animals and human cells suggest exposure to microplastics could be related to cancer, heart attack, and reproductive problems.
A study published in March 2024 issue of the New England Journal of Medicine found that patients who had microplastics in the plaque removed from their arteries had a higher risk of heart attack, stroke, and death.
A Stanford Medicine researcher reported that microplastics in animal and human cells can lead to significant changes in genetic expression. A challenge for future research will be to find control groups without prior exposure to microplastics as micro and nanoplastic particles are ubiquitous.
In an article, “Microplastic Human Dietary Uptake from 1990 to 2018 Grew Across 109 Major Developing and Industrialized Countries but Can Be Halved by Plastic Debris Removal,” published last year in Environmental Science & Technology, Xiang Zhao and Fengqi You present an in-depth examination of human consumption of microplastics globally and suggestions for reduced consumption.
Without question, more research is needed to evaluate the impact of micro and nanoplastics on human and animal health.
Food processors, including flour millers may need to become more aware of how their product and processes contribute to microplastics in the food system. In the meantime, it is important to maintain awareness of regulatory perspectives which may be driven more by social pressures rather than science, as demonstrated by the removal of synthetic dyes by the U.S. Food and Drug Administration (FDA) despite the claim that science does not support the need for their removal from the food system in the United States.
FDA Perspective on Micro and NanoPlastics
FDA reports there are currently no standard definitions for the size of micro plastics or nanoplastics. They are found in a wide variety of shapes, sizes, colors, and compositions, including chemical additives making identification and assessment of their potential impacts challenging.
FDA’s position is that these particles enter primarily through the environment. The author suggests the environment also includes the processing environment through which our raw materials move from grain production through to the mill’s customer.
FDA also believes current scientific evidence does not demonstrate that levels of microplastics or nanoplastics detected in foods pose a risk to human health. The agency asserts that because there are no standardized methods for how to detect, quantify, or characterize microplastics and nanoplastics, many of the scientific studies have used methods of variable, questionable, and/or limited accuracy and specificity.
As discussed in the previous section, the medical research community is in the very early stages of assessment of micro and nanoplastics impact on human health.
FDA indicates the presence of environmentally derived microplastics and nanoplastics in food alone does not indicate a risk and does not violate FDA regulations unless it creates a health concern. FDA will continue to monitor research on micro and nanoplastics in foods and is taking steps to advance the science and ensure our food remains safe.
Steps that FDA might be taking are not known at this time. Elimination of synthetic dyes from food formulations is not technically complicated unless you are challenged with maintaining an established products color. If, however, controlling the presence of micro and nano particles in the food chain is demanded based on either science or public pressure, it will be a seriously difficult and challenging undertaking.
With permission from the publishers, FDA has reprinted “Regulatory Report: Assessing the Safety of Food Contact Substances” from Food Safety Magazine, August/September 2007.
The article identifies protocol for the Safety Assessment of Food Contact Substances and the various agencies within FDA regulating industry to ensure food contact substances are safe from a toxicological perspective.
It is impossible to establish with complete certainty the absolute harmlessness of the use of any substance and so it is with micro or nanoplastics.
Micro and Nano Particles Found in Wheat Flour
Aysha et al reported observing 12 types of micro/nano particles in wheat flour that are identified under “Name” in the table on p. 7. A brief description/explanation and food uses primarily associated with food packaging is included in the table.
Their study compared branded and non-branded commercial wheat flour samples in Dhaka, Bangladesh. The average microplastic particles observed were 4,578 kg of flour with branded and non-branded flour averaged 2,747 and 6,409 particles per kg, respectively. How this level of microplastics contamination compares globally is not known but does indicate further study may be warranted.
Potential sources of Micro and Nano Plastics in Flour
As suggested earlier, the environment is a major source of micro and nanoplastics, as discarded plastics degrade in size in the environment. Synthetic polymers and rubber products make up components in seed and agri-chemical handling, as well as planting, harvesting, and storage equipment.
Similarly, mills utilize synthetic polymer components in milling systems. Buckets in bucket elevators, drag conveyor paddles, and rails, screw conveyor liners, spouting, and wear plates, etc. include synthetic materials that wear or break down with time and use.
Rubber and/or various synthetics are part of valves from various types of specific gravity separators requiring sealed outlets for various fractions in our cleaning operations.
Often, vibrating or oscillating machines rest on flexible synthetic mounts. Air filter socks, actuators valves for cleaning filters, and sight glass connections may contain synthetics that can find their way into finished product. Sifter clothing, frame liners, flexible socks, and cleaners in sifters and purifiers may also contain synthetics that come in contact with mill stocks. Various seals and adhesives for sieves, conveyor tops, hand-hole covers, and sleeves inside couplings for pneumatic conveying tubes, may be sources of micro and nano particles. Belt drives, roll brushes, saddle blocks, and cabinet liners may be constructed with potential sources of micro and nanoplastics in flour.
Conclusion
While micro and nano particles in flour do not appear to be on the radar as an issue in the near term, be vigilant to changes in perspective of third-party food safety auditors, FDA, and your customers. Remember that food-grade, FDA- or EU-approved does not mean materials in your process will not wear or abrade, creating micro or nano particles in your flour.
In the meantime, keep your process in good order by monitoring and replacing compromised or worn components with the potential to contaminate your product. Avoid having a customer or auditor identify problems in your milling system.
Dr. Jeff Gwirtz is CEO of JAG Services, Inc., an international consulting company in Lawrence, KS; 785-341-2371; jeff@jagsi.com. He also is adjunct professor in the Department of Grain Science and Industry at Kansas State University, Manhattan.
References
Aysha, Sifat; Sultan, Maisha Binte; Bhuiyan, Md Arifur Rahman; Toha, Mohammad; Ria, Ramisa Tasnim, “Do we unknowingly eat breakfast that contains microplastics? Unveiling the microplastic contamination in commercial flour.” Food and Humanity, 2024, Vol.3, p.100333
ISSN: 29498244; DOI: 10.1016/j.foohum.2024.100333
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