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Pollution

Tiny Bits Of Plastic Found In Table Salt In China

Pollution: Sea salt sourced from the ocean might be delivering a dose of plastic to dinner plates

by Sarah Everts
October 28, 2015 | APPEARED IN VOLUME 93, ISSUE 43

CORRECTION: This story was updated on Nov. 9, 2015, to correct the amount of plastic particles found per pound of salt in the different tested sources.

Diners in China who season their meals with sea salt may be unwittingly consuming microscopic pieces of plastic pollution.

BOGUS BRINE
09343-notw7-microplastic.jpg
Credit: Environ. Sci. Technol.
Pieces of microplastic contaminating table salt in China sourced from the sea (left) and from lakes (right).

When researchers analyzed fifteen brands of common table salt bought at supermarkets across China, they found among the grains of seasoning micro-sized particles of the common water bottle plastic polyethylene terephthalate, as well as polyethylene, cellophane, and a wide variety of other plastics (Env. Sci.& Tech. 2015, DOI: 10.1021/acs.est.5b03163).

The highest level of plastic contamination was found in salt sourced from the ocean: The researchers measured more than 250 particles of plastic per lb of sea salt. The team, led by Huahong Shi of East China Normal University also found tiny particles of plastic in salt sourced from briny lakes, briny wells, and salt mines, although at lower levels—between 3 and 165 particles/lb.

Shi and colleagues argue that plastic contamination originates from the vast amount of plastic pollution floating around marine environments where sea salt is sourced. For instance, bits of plastics might abrade from larger objects, such as water bottles, dumped in the water or they might come from cosmetic products, such as face washes, that use plastic microbeads as exfoliants. The researchers add that other points of entry for plastic contamination are also possible, including during salt processing, drying, and packaging.

Given that manufacturers typically extract sea salt from ocean water by evaporation—a process that leaves everything behind but water—microplastic contamination of sea salt is likely prevalent outside China as well, says Sherri Mason, who studies plastic pollution at the SUNY Fredonia. “Plastics have become such a ubiquitous contaminant, I doubt it matters whether you look for plastic in sea salt on Chinese or American supermarket shelves. I’d like to see some ‘me-too’ studies.”

According to Shi’s team, if a person were consuming Chinese sea salt at the maximal salt dose recommended by the World Health Organization, then that person would ingest about 1,000 plastic microparticles annually. This is still less than the estimated 11,000 particles of microplastic ingested annually in Europe by consumers of shellfish, which can get contaminated by the tiny bits of marine pollution, according to a report released last year.

Given that there are heavy metals and other chemicals of concern in plastic pollution, it’s wise to minimize the entry of plastic into the food chain, Mason adds.


This article has been translated into Spanish by Divulgame.org and can be found here.

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Comments
Enviro-Equipment, Inc. (October 29, 2015 10:33 AM)
Unfortunately using sea salt when cooking is all the rage now. However, when word of this story makes its way around the world via new sources and/or social media, something tells me the fad of sea salt will come to a rather abrupt end as no recipe I know calls for tiny particles of plastic.
Robert Buntrock (November 5, 2015 4:32 PM)
Agreed. I could never figure our how the sea salt fad caught on given that table salt (aka "fossilized" sea salt) is pure and sea salt isn't, plastics or not. Since the proponents of sea salt tend to be concerned with food purity and maybe just a bit chemophobic, their rationale for using sea salt is dubious.
K.Williams (October 31, 2015 2:19 PM)
There is research ongoing in the US that has found microplastic contamination in seafood. It's interesting that this is a no-brainer result of degrading plastic in the environment, and yet people are surprised. As a society we really are quite stupid. We regularly compromise our habitat and food sources for economic gain, and companies led by human beings lead this degradation. We have perfected rationalization so that we would rather endanger human health and lives rather than corporate gain and profit.
Gavin (November 3, 2015 8:31 AM)
In the original abstract it states "The microplastics content was 550–681 particles/kg in sea salts, 43–364 particles/kg in lake salts, and 7–204 particles/kg in rock/well salts.",

How does CE&N calculated "The researchers measured more than 1,200 particles of plastic per lb of sea salt. The team, led by Huahong Shi of East China Normal University also found tiny particles of plastic in salt sourced from briny lakes, briny wells, and salt mines, although at lower levels—between 15 and 800 particles/ lb."

it suppose to be 500 particles of plastic per lb of sea salt, not 1200. all your calculation are wrong.
Ryan (November 4, 2015 2:14 PM)
550 particles/kg = 1212 particles/lb
Chuck (November 4, 2015 6:34 PM)
you multiplied when you should have divided by 2.2.
Jim (November 4, 2015 11:12 PM)
1 kilogram = 2.2 pounds
550 particles/kg = 250 particles/lb
I think Gavin is right. I think Ryan and C&EN are wrong.
Dale (November 5, 2015 9:00 AM)
What happened to our system of education?
Emma (November 5, 2015 9:48 AM)
550 particles/lb = 1212 particles/kg
kdog (November 5, 2015 10:00 AM)
Oh, c'mon. A pound is smaller than a kilogram, not larger:
(550 particles/kg)(1 kg/2.2 lb) = 250 particles/lb

But why would C&EN even attempt to convert to imperial units? We're supposed to be educated readers who are comfortable with metric units.
Jerry (November 5, 2015 1:17 PM)
No, you got that back to front, 1kg~=2.2 lb, so ~550/2.2 = ~250 particles/lb
Greg (November 5, 2015 5:28 PM)
I get something different. (550 particles/kg)*(1kg/2.2lb) = 250 particles/lb
S. Everts (November 7, 2015 6:41 AM)
Sarah here, from C&EN. Chuck is correct. We mistakenly multiplied by 2.2 instead of divided by 2.2. Sorry about that, folks. We'll correct it ASAP. In the meantime, the correct figures are as follows:
The researchers found that there are 250 plastic particles per pound of sea salt.
When you combine the ranges of plastic particles found in rock, well and lake salts, the team found between 3-165 particles of plastic in these salts.
Rachel (November 5, 2015 3:37 AM)
Ryan, is it a kind of a joke, or, like my students you multiply when you should divide?
Jerry (November 5, 2015 7:21 AM)
Calculations seem odd to me but I am a chemist not mathematician. In sea salt, 550 to 681 particles per kg I would calculate to be 250 to 309 particles per lb.
S. Everts (November 7, 2015 6:47 AM)
Sarah here, from C&EN. Chuck is correct: We mistakenly multiplied by 2.2 instead of dividing by 2.2. Sorry about that, folks. We'll correct in online ASAP. In the meantime, here's the correct information:
The researchers found at least 250 plastic particles per pound of sea salt. When you combine the ranges for rock, well and lake salts, the team found between 3-165 particles of plastic in these salts. Again, sorry about the error.
Todd (November 30, 2015 10:07 PM)
Interesting work and good to see it published, but the tone and conclusions are hysterical.

"According to Shi’s team, if a person were consuming Chinese sea salt at the maximal salt dose recommended by the World Health Organization, then that person would ingest about 1,000 plastic microparticles annually"

Using 1.38 g/cc as the density of PET (the most prevalent plastic identified in the samples), the size of the particles cited in the article (55% diameter <200 microns) , some geometry (V = 4/3*pi*r^3) and unit conversions one finds that the individual ingesting 1000 particles per year receives a whopping dose of ... 5.8 mg of plastic per year (less if one assumes lower density plastics like PE or PP, or that the diameter of the particles is less than 200 microns).

Look, I'm not a fan of polluting our oceans and I think it is common sense that we should be striving to manage our plastic waste better than we are today. But a balanced assessment of the risks suggests there isn't at present much to worry about from sea salt.
Harry Romijn (April 10, 2017 4:50 AM)
And you have ZERO hesitation to feed that to your (grand) children ?
That's why I refused several suppliers of sun-dried sea salt.

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