Microplastics in Table Salt. What Can We Do About it?

A very interesting video (website below) on the presence of microplastics found in table salt was sent to me via Whatsapp chat by Dr. Vythi, a friend of mine who is in medical practice.

https://www.youtube.com/watch?v=2YjX2TIyKUI

I gave it a flicker of thought, and thought I should pen  my personal view on this issue.

I fully agree that micro-plastics found even in the ocean waters is the most ubiquitous type of marine environmental pollution, and they may land up in the salt harvested from sea water.  Plastics come in all forms of shapes and sizes.

There are at least 6 types of high and low density plastics in use today.

But I think the most common plastics in use today even in Malaysia are the polyethylene terephthalate (PETE or PET) I use these often myself.

Others commonly in use are the polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), polylactic acid (PLA), polycarbonate (PC), besides acrylic (PMMA). But I think PET is probably the most widely produced plastic in use globally today.

Life Span of Plastics:

Unfortunately most plastics floating in ocean waters take a very long time to degenerate even by the action of ultraviolet light, heat, oxidation and sea water, and even if they do, they take anything between 20 to 600 years or even up to 1,000 years to break up into very tiny physical fragments called micro-plastics.


Over time, they may even fragment further into much smaller sizes almost at molecular levels called nano-plastics which I shall explain later.

It is estimated plastic food wrapper and containers take 20-30 years to degenerate, plastic straws 200 years, plastic water bottles 450 years, plastic utensils 450 years, nylon fishing lines some 600 years, and caps and lids made of plastics 450-1,000 years. The list goes on. 

Plastics whichever form are highly stable except when burnt at high temperatures. When we talk about their degeneration in the ocean, ultra violet light from the sun, salt water, the constant mechanical motions of the waves, and the oxygen, merely tear them up physically, but not chemically. 

They then break into micro or even nano sizes. This action is very much similar to water softening, teasing, and breaking up pieces of paper into their fibers. But they remain chemically the same in composition.

The reason why plastics are so difficult to degenerate chemically is because plastics are complex polymers made of repeating chains of the same molecules joined together. This makes  them quite difficult to break up or dissolve in water. Their polymer strength makes them very durable for decades, and even into tens of hundreds of years.

Cleaving the Chain:

However in recent years it was found that certain bacteria do have enzymes that is able to cleave apart these polymer molecular chains.

The ability of a few fugal species, and a novel bacterium called Ideonella sakaiensis 201-F6, can enzymatically degrade PET by hydrolyzing PET into mono (2-hydroxyethyl) terephthalic acid, and ethylene glycol.  In simple language, the bacteria and fungus chemically break down the plastics for their energy and a source of carbon. 

Biodegradation by bacteria may give us some hope, although not practical as yet when dealing with these almost indestructible plastic for reasons we shall not discuss here.

Burning:

Burning the plastics makes the problem worse by polluting the air with toxic and acrylic fumes. A few of these pollutants such as hydrogen cyanide, mercury, polychlorinated biphenyls (PCBs), dioxins and furans are very poisonous, and persist for long periods of time in the environment and have a tendency to bio-accumulate into the food chain. Dioxins are the most toxic substances known.

Toxicity:

As for human contact, we have no direct study on this, although microplastics have been found in almost all sources of water and on agricultural lands. They have also found their way into sea salt, shellfish, tap and bottled water, beverages, in honey, and even in the air. Thus, inhalation and digestion of microplastics are worrisome as health pitfalls.

Their kinetics in terms of uptake, distribution, accumulation, retention, and their interaction with tissues and organs, their metabolism, excretion and toxicity depend on many influences. These will depend on their sizes, geometry, chemical nature and surface properties, their bio-persistence, as well as with other chemical substances  or toxic agents they may have gathered from the environment along the way.

Even though  human exposures to microplastics is prevalent, the result of animal studies may not be directly translated into humans because  animals and wildlife studies may  not necessary be accurate proxies dues to differences in physiology and immunological make-up among different animal species and their biological responses are different to different  exposure scenarios.

Furthermore, unlike in controlled clinical trials as for new drugs, it is not ethical for scientists to apply the same experimental procedures for  microplastics, and then attempt to match them against a placebo to compare the results, and to evaluate their impact on  humans.

Scientists can only conduct observational epidemiological studies which can be reactive with other causative factors that limits single or restrictive causation.

Even though there are different types of observational studies, generally researchers are interested in measuring exposures and their health after-effects. They may also be interested at looking at other relevant information in communities  who are going to live their lives under such exposures.  


It would thus be difficult attempting to establish whether or not there is a statistical co-relationship between long-term micro or nano-plastics exposure and  health outcomes.

In the worse scenarios, exposure can be an occupational risk where workers are exposed to high levels of any toxicants as part of their job. They become custodian species like guinea pigs while scientists wait and watch their outcomes.    

                                                                                        

Health Impacts:

The most worrying issue is, we do not know what their impacts on human health would be,  even though they are non-soluble in water, and are thus not easily transferred across the human intestinal gut when the micro-plastics are large enough, but what happens when they get into nano-size which I shall briefly explain a little later.

A search of the literature showed that not much is known about micro-plastics itself,  whether found in salt as shown in the video, in the water or even in the air, less so if they appear as nanoparticles.  For this, we have even lesser understanding on their pathological significance.

The best I know is the NOAA Marine Debris Program which is underway on their impact on the water environment and their effects on marine life. But what about their repercussions on humans? I am afraid we have little lead from the limited literature, not in those I have searched so far.

Nanoparticles:

There may be increasing breakdown of plastics from micro into almost molecular size nanoplastics. Nanoparticles are really tiny sizes between 1 and 100 nanometres with a surrounding interfacial layer.

 

The interfacial layer is an integral part of nanoscale matter, fundamentally upsetting all of its physical and chemical properties. The interfacial layer characteristically consists of ions, inorganic and organic molecules. Their behavior would be different from the micro-size particles.

The width of  fine particles extent a scale between 100 and 2500 nanometers, whilst ultrafine particles are sized between 1 and 100 nanometers. Nanoparticles may or may not demonstrate size-related properties that are seen in fine particles.

Notwithstanding the hazards of nanoparticles, they can also be useful in medicine.

In recent years nanoparticles  have  wide applications in medicine, their role ranges  anything from generating fluorescent biological labels such as biological markers and molecules in research and diagnosis of diseases, to  drug and gene delivery systems  for chemotherapeutics and gene therapy.

 They are also used for the detection of disease caused by organisms and biological systems, for diagnosis and also for the discovery of proteins.

Their isolation and the purification in biological systems in molecules and cells are also used in exploring the DNA structures, besides their applications in studying drug kinetics, and their functions in genetic engineering and tissue manipulations.

 

Nanoparticles are also used in MRI research, and for the destruction of tumour with heat or alongside with drugs among others.

But nanoplastics or other nanoparticles are a double-edged sword, wearing the faces of Dr. Jekyll and Mr. Hyde. They can also be very destructive to health as much as they are useful in medicine.

Nano-size particles such as nano-plastics are so small that they can also be a health hazards in their ability to penetrate the skin, intestines, and henceforth find their way into the brain and nervous systems, into the lungs, liver, kidneys, eyes, and other tissues, organs and systems, disrupting their functions and normal physiology.

So what can we do if we are distrustful of the presence of micro-plastics in our dinner salt?  We shall discuss that later, but before that, let us look at some of these issues on the body systems.

Pathophysiological Outcome:   

                                                                                                                                                                                                                  

One potential danger pertaining to the presence of microplastics of 5 microns across, and worse of all, probably nano-plastics as well in the range of less than 100 nm size in the aquatic environment, is they have already shown their presence into the human food chain through sea water such as salt as shown in the video 

Although some studies have been done on micro-sized plastics, very little study have been done on nano-sized plastics in sea water and in the air. 

This issue does worry scientists and consumers alike as these nanoparticles may affect the lungs, brain, liver, kidney and other organs as already mentioned. But they may also have other impact such as on the absorption of nutrients and subsequently on nutrition, and probably on drug absorption as well for which a dose adjustment may be required if they hinder the pharmacodynamics of drugs 

Gastrointestinal Physiology:

There is a strong possibility nanoplastics or microplastics may block the absorption surface area of the intestinal villi The villi are small, finger-like protrusions that cover the surface of the lumen of the small intestine.

In humans, each villus is approximately 0.5–1.6 mm in length and again they have many microvilli projecting from the enterocytes of its epithelium which mutually shape the striated or brush border.

Each of these microvilli is much smaller than a single villus. The intestinal villi are much smaller than any of the circular folds in the intestine.

In gastrointestinal physiology, we know that the villi increase the internal surface area of the intestinal walls so that there is a greater surface area for the absorption of nutrients and also for drugs.

Any increased absorptive area is advantageous because digested nutrients such as monosaccharide, fatty acids, amino acids alongside with vitamins and minerals can pass into the semipermeable villi through diffusion, which is operative only at short distances.

In other words, any increased surface area when in contact with the fluid in the lumen will decrease the average distance traveled by nutrient molecules, so efficacy of diffusion including via active transport mechanisms increases.


The villi are linked to the blood vessels so that nutrients can be transported away through the portal vein.

There is a very likely chance that, since these micro-plastic is not soluble, neither can they be digested by the intestinal juices nor degraded by the gut microbiota, unlike all food substances, they being micro-sized, may accumulate and aggregate over the absorption surface of the villi and seriously affect absorption of nutrients over a period of time. 

As said earlier, the physical and chemical properties of nano-particles including those of plastics change when the reach nano-sizes. Their behaviour may no longer be the same as just micro-plastics. 

They are unlike the soft and soluble fecal residues that can be removed or rubbed off by the constant peristaltic movements in the intestines. Being micro to nano-sized, and insoluble, they may have a tendency to adhere by adhesion and cohesion molecular forces over the entire surface of the intestines and villi aided by sticky fecal residues.

In short technical term, we may call this as bioaccumulation and bioamplification phenomenal trends

This is a hypothetical  strong possibility which we as medical scientists and researchers do not yet know

We also have little clue if their presence in the food or gut may change the epigenetics how the genes is going to express and respond to these changes, such as whether or not there is a correlation between colorectal cancer and the presence of accumulative nano plastics lodged in the colon.

I think as scientists and doctors we have valid concerns over these issues.

What can be done!

There is nothing that can be done, except the global ban of all plastics. But if microplastics are found in our kitchen cooking salt, there is much everyone can do.

Here is my simple suggestion well within the ability of everyone. It is so simple.

Make a highly concentrated salt solution by dissolving salt in water. Unlike sugar where the solubility in water increases with temperature, the solubility of salt in water increases only slightly even by boiling.

The solubility of sodium chloride (salt) at nearly freezing water is 35.65 g per deciliter of water, whereas in boiling water, its solubility increases to a mere 38.99 g per deciliter of water.

 

At near zero degree Celsius of water, about 175 grams of sugar can be dissolved up to an end point of 500 g. sugar at boiling temperature.

Thus it is unnecessary to boil the salt solution. Merely stir a good amount of salt in water at room temperature until no more salt can be dissolved. That would be already a saturated solution of salt.

We also bear in mind that boiling salt water at 100 degree Celsius with micro and nano-sized plastic inside, does NOT destroy or dissolve the plastic.  Only the salt will dissolve whether at room or at boiling temperature of water. 

The complex polymer structure of plastics makes it very resistant for the plastic to breakdown, whether by boiling, or allow it to decompose naturally as mentioned earlier.

 So now we have an advantage. Assuming we now have a very concentrated solution of salt solution contaminated with micro-plastics. What do we do next?

All we need is just filter out the salt solution using a home-made cloth filter, the same filter for making coffee.  The filtrate will almost be free of micro-plastics.

We just use only the filtered concentrated salt solution for all our cooking, since it is not  necessary that  salt granules or salt crystals need to be added into the cooking as is normally done. 

After all, when water is added into cooking we still have to add salt. So we might as well add the filtered concentrated salt solution which is free from micro plastics as the cooking water.

There is also no need to boil down the salt solution until only salt crystals are left behind for use. This would be a waste fuel and time boiling down the salt solution to get back the salt crystals when salt solution is just as perfect for cooking.

As mentioned, during cooking both water and salt are added, not just salt alone, unless you want to sprinkle extra salt into the cooked food. 

However, as a side-advice, please limit the daily intake of salt to slightly less than 4 grams a day which will give us about 1500 mg of sodium a day. This restriction of salt intake is for various health reasons.  But we shall not discuss the mechanisms of how salt acts on the pathophysiology of salt-related diseases here as it is irrelevant in this short discussion on micro-plastics in salt.

Drinking Water:

As far as micro plastics found in drinking water is concerned, this can easily be solved by using water filters, especially carbon filters or ion exchange filters that can block any particles, or even bacteria down to 2 microns in size. Some can filter down to the tune of just 0.001 microns. Using a filter should not be a problem.

But what Dr. Vythi showed me in the video was not micro-plastics in drinking water, but in common salt (sodium chloride).


Obviously we cannot filter common or table salt, but perhaps we can use a sieve to separate the solid salt from the micro plastic particles since salt crystals would be larger, but this is not as effective as filtering out a solution of salt. 

Since most of the micro-plastics in sea water from which salt is harvested, is between 15 – 25 microns, these can be filtered out using a home- made cloth filter as already discussed, the same kind of cloth filters used in Chinese coffee shops in Malaysia and Singapore to strain coffee. 

A cheese cloth for making cheese or tofu may also be used. The mesh or pore size of these cloth fabric is approximately between 10 – 20 micron, but can vary according to the type of cloth used.

The size of a human red blood cell is about 5 microns across, and a human hair is about 50 - 75 microns, and the smallest bacteria is Mycoplasma genitalium has a diameter of 200–300 nanometer across, while the largest bacterium in terms of length is Thiomargarita namibiensis that has a diameter of 100–300 micrometers (0.1–0.3millimetres) just for comparison. 

But when plastics break down to nanoparticle sizes of just 1 and 100 nanometres, almost into molecular sizes, then there is practically nothing we can block them. Almost no home-made filters, or commercial filters can separate  them.

Let’s hope we will not encounter this problem.

lim ju boo