Microplastics in Table Salt

Microplastics are everywhere. These miniscule particles, which are to plastic what sand is to glass, have become nearly ubiquitous in both land and sea. Since 2016, 4.8-12.7 million metric tons of plastic entered the ocean each year [1], and the average adult may be ingesting 2,000 microplastics per annum [3]. It would then come as no surprise to learn that microplastics have entered our food chain through the fish we consume. More recently, we discovered that they are even present in table salt [1, 2]. As the effects of microplastics on humans remain unclear and our increasing exposure to them is inevitable, gaining a better understanding of their origins and how to mitigate exposure may be crucial for our health. 

What are microplastics and where do they come from? 

The term “microplastics” was coined in a renowned 2004 article from Science Magazine [2], whose authors discovered degraded plastic particles in coastal and marine ecosystems for the first time.

Put simply, microplastics are classified as fragments measuring less than 5 mm in diameter of larger plastic items (e.g. bottles, containers, bags, you name it) that have been degraded and broken down in the environment over time [2]. Although plastics can last up to 600 years before completely deteriorating [4], the formation and release of microplastics occurs throughout this degradation process. In the oceans, physiochemical changes due to environmental weathering such as photodegradation from UV exposure can alter the properties of plastic leading to oxidation and particle release [5]. 

Plastic can enter the oceans in several ways [6]:

• Throwing plastic in the regular trash instead of recycling: since most rubbish is sent to landfills, the light weight of plastic often causes it to be blown away, eventually finding its way into rivers or drains which generally lead to the ocean. 
• Littering:  Tossing plastic on the ground almost ensures that it will be carried into a stream, river or drain and end up in the ocean. 
• Products going down the drain:  Daily use products such as wet wipes, cotton buds, and sanitary products can degrade into microplastics. As mentioned above, most drains lead to the ocean.
• Microfibers from washing clothes: These are too small for filtration systems in waste water plants to catch and reach streams, rivers or the ocean. 

Why Should You be Concerned?

The chemical properties of microplastics are such that they do not break down very easily [1]. As a result, microplastics can bio-accumulate, which means that they are not fully excreted and accumulate in various tissues. This has been shown in marine species, and more recently, in human tissues [7]. That being said, little is known of the health risks associated with ingesting microplastics in humans. Research conducted on rats and fish suggests that microplastics can activate an inflammatory response and damage cells [7]. Depending on particle size, microplastics [8]: 

• May cross the blood brain barrier: this may have dramatic implications for neurodegerative diseases such as Alzheimer’s. Read our recent article on Inflammatory Alzheimer’s to learn more about how inflammation can contribute to the disease. 
• May cross the placenta: This implies that microplastic exposure might be transmitted from mother to child during pregnancy. 
• May cross cell membranes: This just means that if particles are small enough, they may move in and out of cells as they please. 

It is important to remember that there have been no studies explicitly investigating microplastic ingestion in the human body, so all effects on health are inferred. 

So, Are There Microplastics in Table Salt?

As it turns out, several studies have detected microplastics in table salt worldwide [2,3,4]. A recent review examining 11 Taiwanese salt products found varying levels of contamination in all of them [1].  Another paper noted the detection of microplastics in over a hundred brands, globally [7], citing table salt as one of three major sources of microplastic exposure along with water and inhalation [7]. In addition, an investigation of 39 salt brands revealed that Asia may be a hotspot for plastic pollution and exposure to microplastics [3]. 

Salt is a universal household staple that can come from three sources: the sea, lakes or rocks. There seem to be two major pathways that microplastics enter table salt [1]:

1. Environmental Contamination (i.e. from the ocean or lakes) as a result of plastic pollution in the sea which leads to the formation and omnipresence of microplastic particles. This is the main source of microplastics entering sea salts and lake salts
2. Contamination during processing and packaging during which particles “leak” from the use of certain plastic components, tools, and final packaging materials. This is the suspected source of microplastic in rock salts. 

What Can You Do About It?

Some good news is most researchers still agree that the levels of microplastics in the environment are not sufficient to impact human health [7]. However, these numbers are expected to rise as plastic waste is projected to nearly double by 2040 [7]. So, what are some actions you can take to reduce your exposure to microplastics?

• Change what salt you buy: Buy high quality salts or rock salts. Ideally, opt for non-plastic packaging. 
• Get reusable water bottles: A glass or stainless steel bottle can disincentivise you to purchase plastic water bottles, and save you some money in the long run.
• Avoid food/drink in plastic packaging: Purchase drinks in glass or stainless steel bottles, loose produce, whenever possible.
• Get glass/wood tupperware: You can easily order a set online, preferably with a glass or bamboo cover and silicon lining. 
• Store food and dry goods in glass containers/jars: We are learning that microplastics can leak from plastic containers, so minimize these asmuch as possible
• Use food grade silicon bags instead of traditional ziploc or other plastic bags: These can be purchased online or at most grocery stores. 

What Salt Brands are the Best ?

Based on the research reviewed here, salt sourced from Asia may have the most microplastic contamination followed by Pacific Sea Salt, Celtic Sea Salt and Himalayan Rock Salt. So, what brands do we recommend when thinking of reducing microplastic exposure? 

• Redmond’s Real Salt: This brand sources their salt from an ancient salt deposit in Utah, which has not been exposed to the ocean. In fact, one paper found salt from Utah to have some of the lowest levels of microplastics [10].
• Jacobson Salt Co: Their salt is sourced from the Oregon Coast. Although the Pacific ocean may contain higher amounts of microplastics, the company claims to filter out these particles with 0.5-5 micron filters [11]. 

A note about Himalayan Rock Salt: Sourced from salt deposits in Pakistan, this salt is worth mentioning because of its increasing popularity. Even though it is a rock salt and expectewd to have little contamination, a recent study demonstrated that one brand contained some of the highest levels of microplastics [10]. This could be due to processing and packaging methods, so it is important to seek out high-quality products that are packaged with non-plastic materials.

As a reminder, this is not an advisory to avoid all other table salts because we simply do not have enough information yet. We are all in this learning process together, and the aim of this article is to provide you with the most current knowledge to help you make informed purchasing decisions. 

Conclusions:

Microplastics are everywhere and there does not seem to be a slowdown in sight. To better understand the implications for human health, more studies are desperately needed. Since contamination of sea products like table salt are only likely to increase, taking steps to mitigate your exposure may protect you in ways we cannot yet explain. Opting for rock salts and higher quality salts can reduce contamination from both the environment and manufacturing practices. If you are unsure of how this can affect your cognition, speaking to a doctor or dietitian trained in functional medicine can make a significant difference. Contact the Amos Institute today to make an appointment with a dietitian trained in a functional medicine approach to health.

References:

1. Lee et al., 2019: https://doi.org/10.1038/s41598-019-46417-z
2. Thompson et al., 2004: https://doi.org/10.1126/science.1094559
3. Kim et al., 2018: https://pubs.acs.org/doi/abs/10.1021/acs.est.8b04180
4. Ward & Reddy, 2020: http://dx.doi.org/10.1073/pnas.2008009117
5. Zhnag et al., 2021: https://doi.org/10.1016/j.envpol.2021.116554
6. Daly, 2022: https://www.wwf.org.uk/updates/how-does-plastic-end-ocean#:~:text=Litter%20dropped%20on%20the%20street,plastic%20surge%20in%20our%20seas.
7. Zhang et al., 2020: https://doi.org/10.1021/acs.est.9b04535
8. Lim 2021: doi: https://doi.org/10.1038/d41586-021-01143-3
9. Karami et al., 2017: https://doi.org/10.1038/srep46173
10. Kosuth et al., 2018: https://doi.org/10.1371/journal.pone.0194970
11. Jacobsen Salt Co, 2019: https://jacobsensalt.com/blogs/news/how-jacobsen-salt-co-water-filtration-prevents-microplastics