Table salt is a part of our daily life, and we are a subject to a great exposure to microplastics via its consumption without knowing about it.
Since the start of its marketing in 1950, the global plastic production has increased exponentially, reaching for example 348 million tonnes in 2017. Mostly neither collected nor recycled, most of the waste ends up in waterways to reach the oceans.
Designed to be durable and resistant to very high temperatures without degrading, the plastic has become the persistent pollutant in the most diverse environments: air, water and soil. Driven by rain, water currents, winds … etc, the plastics end up in the seas and oceans.
Our oceans receive a total of 4.8 to 12.7 million tonnes of plastic annually, of which 1.15 to 2.41 million tonnes come directly from fresh water. Several studies have been conducted over the past two decades on the problem of plastic debris, however, it was in 1990 when the degradation of plastics was thoroughly analyzed to finally consider microplastics as powerful pollutants.
Microplastics are characterized as plastics or fragments of small proportions, with dimensions less than 5mm. Dozens of analyzes have identified the types of plastics that are most common in the oceans. Polypropylene, polyethylene, polystyrene, polyvinyl chloride and polyethylene terephthalate are the synthetic micropolymers that have the most ability to resist in the oceans, reaching different types of organisms. As a result, they end up accumulating in our food chain.
Several studies have been conducted in recent years to understand the potential impacts of these compounds on human health. Among these studies, a hypothesis by a group of Chinese researchers in 2015 proved the contamination of commercial table salts based on salt water because the oceans, where they come from, are highly polluted by plastic debris.
In their research, they analyzed 15 brands of sea, lakes and rock salts all over China and they found 550 to 681 micro-plastic particles in the kilogram of sea salts, 43 to 364 particles in the kg of lake salts and 7 to 204 particles in kg of rock salts. Since that result, further research has been done at several global sites.
Recently, a group of Portuguese researchers evaluated the degree of contamination present in traditional Portuguese table salts according to their origin and the type of salt. Fourteen samples were then selected: seven from thin-salts and seven from coarse-salts, corresponding to seven distinct regions of Portuguese territory.
Their results revealed that in the table salt analyzed, the most abundant plastic particles were fibers (64%) and fragments (35%). The concentration of microplastics (MP), depending on the origin of the salts, varied between 595 and 5090 MP / kg in sea salt, and in Rio Maior’s well salt, it varied from 3325 to 6430 MP / kg, and according to the type in salt, the concentration of MP in the fine salts was 2320–6430 MP / kg and in the coarse salt 595–3985 MP / kg.
The World Health Organization recommends a maximum daily salt intake of 5.0 g / day. However, the world’s population is consuming even more and should take these studies into consideration and rethink about their eating habits.