On the Purity of Sea Salt

Sometimes we get inquiries from our customers at The Meadow which, in the interest of promoting better awareness about good culinary salt, merit a public response.  Jason L asks about the purity of sea salt. My book, SALTED, to be released this October 12 (more on that in a later post!), explores this question in detail, and provides solutions that lead us toward the ultimate goal of tastier, more exciting, satisfying, and nutritious food.


I have a couple questions about salt production and I’m hoping you can answer them.  I’ve had an interest in salt for a while and how it is made. I’m curious about two things.

1. How can you tell where sea salt is made?  Coastal water pollution is a problem all over the world.  Why should I assume that “French sea salt” (or any sea salt) is made from clean waters?  Is there a way to find out and/or verify?

2. Solar evaporation is a very old and common practice for making salt.  But how do they keep stuff out of the ponds?  Bird poop?  Bugs?  Dirt? Whatever else?  It seems like creating something with that much exposed surface area is bound to get contaminants. I am hoping you can shed some light on these things for me.  I haven’t been able to find any answers anywhere else on how salt production is kept clean.  Michael Pollan writes about making brown salt from polluted water.  Everyone writes about gathering crystals by hand, etc., but no one says anything about how salt is made clean.

Hi Jason,

1.  Regarding the purity of salt:

The first thing you have to do define “pure” as it relates to salt.  Consumers should consider impurities as either: a) contamination from environmental sources such as pollution, run-off etc.; or b) from chemicals deliberately added in to salt as part of its processing for industrial and consumer markets.  In my opinion, the former is inexcusable.  The latter is, at best, a necessary evil (e.g. salt iodization as part of strategic global health initiatives in impoverished countries), and at worst yet another example of the unnecessary industrialization of our food supply.

The “French sea salt” you refer to above could come from either of two seas: the North Atlantic on the west coast, and the Mediterranean to the south. The Atlantic waters are very clean, and the French sea salts made there are in turn filtered through exquisite marine wetlands that are among cleanest and closely protected in the world.  The French sea salt from the  Mediterranean comes from far less pristine waters, and the vast majority of it is harvested using heavy industrial equipment, though there are important exceptions (such as fleur de sel de Camargue).

The term “sea salt” itself reveals little about the purity of the salt. The vast majority of salts around the world sold as sea salt are in fact manufactured using industrial processes and standards. Industrially made sea salts can come from polluted waters such as the San Francisco Bay, and may be further contaminated during the harvesting process, which employs heavy, diesel-powered equipment. After going through a refining process to eliminate the industrial pollution that gets in them during evaporation and harvesting, industrial salt companies may add chemicals back in to the refined salt to keep it free-flowing, to make it white, to iodize it, etc. etc.

It’s important to recognize that chemically pure sodium chloride (NaCl) is NOT a natural salt from either a culinary or dietary standpoint, and such a thing did not even exist prior the chemical-industrial revolution of  the late 1800s. Nature does not make anything resembling the refined, 99.8% and higher sodium chloride salts produced by the chemical giants who have taken over the manufacture most of the world’s salt.  Natural salts have a host of trace minerals (upwards of 15% sometimes) and are almost totally devoid of harmful environmental contaminants, and these minerals are part of a salt’s naturally “pure” make-up.  For this reason purity is not itself a terribly helpful term for salt, any more than it would be for rich topsoil, pungent grass, happy sheep, or molding cheese.  The unfathomable complexity of these things offer something far more than purity: they offer wholesomeness.

I look at a host of things when determining whether we should carry a salt in our store, with the ultimate goal of understandings each salt’s suitability for eating. After a salt has won us over with its flavor, beauty, and behavior on food, we look deeper. For many salts we obtain a spectral analysis. Here we keep an eye out for positive things like levels of magnesium, and negative things like levels of mercury and lead.  While heavy metals are very rarely present in levels sufficient for concern–often the levels are the same or lower than in natural rock salts, which predate man by several hundred million years–they can be indicators of a polluted environment.

But there are other things that are  more important  than a chemical analysis. Serious saltmakers  are far more demanding than any technical specification can possibly reflect.  As fierce guardians of the ecology in which they practice their trade, artisan saltmakers have a deep and nuanced understanding of the dynamics behind the creation of their salt.  No amount of testing has saved Americans from contaminated eggs, produce, and meat because contaminants are part of the very mechanism of industrial food manufacturing—it’s just a matter of minimizing this contamination.  Artisans practice outside of this logic, with criteria for quality organized around the principles of expert knowledge, hand labor, ecological stewardship, and economic sustainability.  Such wholesomeness is at the heart of good salt, and I guess that insofar as its meets these standards, it is “pure.” This logic might be applied not just to salt, but to all food.

2. Regarding the contamination of salts from natural environmental things like birds and bugs:

Most sea salt is made in open salt pans where it is evaporated by the energy of the sun and wind.  All open pan solar sea salts are subject to all the effects of the environment.  A pristine natural environment will buffer salt pans from industrialization, but birds, fish, crustaceans, algae, and pollens are all present in such places.  So, is this a problem?

In a word, No.

Admittedly, no unrefined sea salt will be utterly free of all the things that naturally occur in the this environment. (Fresh, ice-cold water drawn from a mountain spring water will contain organic matter. Water stored in plastic bottles on supermarket shelves will contain no organic matter–though it may contain Bisphenol A and other chemicals.  Which is better?)  But salt makers will often pour clean ocean brine over the salt crystals as they are harvested to rinse them of any unwanted matter.  In other places, seasonal things like pollen from nearby mountains is considered part of the character of the salt, though this, too, is often rinsed out when the salt is going to be sold outside the community. In addition, the natural ecology of a healthy salt pond will help keep things in balance. As the chemical, visual, and taste analyses can attest, the combination of the pond ecology and rinsing in natural brine results in a very clean salt.

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17 Responses to “On the Purity of Sea Salt”

  1. on 25 Aug 2010 at 3:21 pmMaría Eugenia Terragno

    How very interesting! Thank you very much, I’m a big fan of sea salt and I have all kinds of them in my kitchen.

  2. on 26 Aug 2010 at 8:33 pmJason L.

    Mark, thank you so much for taking the time to write such a lengthy and informative post! I’ll look forward to getting your book. The world (and history) of salt is more interesting than I thought it might be. Your answer helped a lot with my most recent blog post. Thanks Again!

  3. on 29 Oct 2010 at 9:47 amMichele Kadison

    This is an excellent article that I am going to pass on to my readers – thank you so much. Several people have written to me questioning the purity of Celtic Sea Salt, as per the last post I made covering the benefits to the thyroid gland. I look forward to reading your book, Salted, and to passing the information on through my blog.

    Michele Kadison

  4. on 16 Dec 2010 at 8:12 pmferdi atienza

    Your article mentioned spectral analyses, what are the usual minerals or matters that you test.
    Thanks for the information.

  5. on 06 Jan 2011 at 1:20 pmKristin

    An interesting read, thank you. You know, with the demand for “Celtic” sea salt up these days, what the chances of counterfeit products (not from you, that is not my point) being sold? I know this is an issue with Olive Oil. What have you seen or heard?

  6. on 15 Jan 2011 at 9:49 pmSammy Youngs

    Thank you for the very informative web. I do however have a very disturbing question..
    I have an allergy to shell fish, crustaceans and all sea food or fish. It only takes 1/40000 of a gram to cause a life threatening reaction. If sea salt is not 100% pure, my life is in danger.
    Is this something that I have to be concerned about?

    It is out of my control if product labels do not say “sea salt” so that I can avoid these
    products. At least Campbells are telling the public that they are using sea salt. Do to that fact, they have a customer, I will not risk my life just to have a bowl of soup.

    Is the government going to require that all food processors list “sea salt” as an ingredient, not just salt?

    This is a very large concern to me and I am sure many other people with my problem. Is there a solution to this new issue?

    Thank you for your time and effort.

  7. on 07 Mar 2011 at 7:31 amwillem bezemer

    There have to be pollutants in unprocessed sea salt! Has any individual / agency bio-researced and quantified just what the residual composition of currently marketed “natural unrefined ” sea salts are?Anyone ? Willem.

  8. on 19 May 2011 at 12:15 pmMark Bitterman

    Willem – The answer is that virtually every commercial salt producer, whether artisan or industrial, is regulated, and has to undergo testing. The thing to get straight is that generally speaking, salt is the wrong place to look for contaminants. Fish, milk, produce, livestock can take in certain substances can indeed concentrate them. But salt does not bio-accumulate pollution like organic things do. On the contrary, the nucleation of crystals excludes the bonds with substances other than the crystals being nucleated, making it very difficult for any contamination to get a foot-hold on the crystal. This is why salts are actually cleaner than the environment from which they are made. Another thing to consider is how little salt you actually eat. The US Dept. Of Agriculture estimates we each eat 4.7 pounds of food a day. Only ¼ of an ounce of that food is salt. If you are interested in finding a source of pollutants in your diet, look to the foods that bio-accumulate, and which you in relatively large quantities. The last thing I’d add is that salt makers are generally profoundly environmentally conscious. Both the productivity and sustainability of their enterprise depends on intact ecosystems. As people who depend on the healthy ecology of the seas, they see themselves as stewards of the sensitive marine lands, and are ardent defenders of it against encroachment industrial and residential interests. Buying good salt helps preserve some of the environments where other foods can grow naturally.

  9. on 19 May 2011 at 12:17 pmMark Bitterman

    Kristin – I don’t think there are any chances of counterfeit salt. Celtic salt is just a proprietary name for common sel gris made in France. Sel gris is French gray sea salt. If it says French gray sea salt or sel gris, it is almost 100% certainly French gray sea salt (sel gris), though nowadays sel gris-style salt is made in many places around the world.

  10. on 31 May 2011 at 10:52 amMark Bitterman

    We do not perform the analyses ourselves, but in a natural salt (rock or sea) one can expect to find almost every earthly element and compound in varying quantities. On The Meadow’s website we have an example of an analysis done on Himalayan Pink Salt, so you can see the wide variety of elements we are dealing with.

  11. on 30 Aug 2011 at 3:39 pmMark Bitterman

    Sammy – This is a rather complicated problem. All of the salts that we carry in our shop are all natural and unrefined, so they range anywhere from 97% to 70% sodium chloride and contain a host of other trace minerals. Many of our salts are also washed with ocean water to remove impurities. Morton’s salt, to compare, is 99.9% sodium chloride, so technically even they are not pure salt though the rest of the percentage is mostly composed of an anti-caking agent. Even rock salts are, in origin, sea salts. In the end, if only 1/40,000th of a gram is enough to threaten your life, I wouldn’t feel comfortable recommending any salt at all except for the most refined such as Morton’s or kosher salt.

  12. on 06 Dec 2011 at 9:28 amDavid Hendrick

    Great article but it still leaves unanswered the part of the potential pollution equation dealing with man-made organics. Does testing for inorganic mercury catch possible methyl-mercury contamination? While it is good to know levels of arsenic, lead, selenium, mercury, and other inorganics the potential for long-term physiological damage from marine pollution comes, in my mind, not from bird poop or inorganic sources but from the hidden organic chemicals present being concentrated with the salt through the evaporative process. It is the man-made, organic-chemical additions to the marine environment most weighty on my mind. I use the slightly pink ancient sea salt mined in Utah. It, at least, gives me the illusion of being relatively beyond the reach of the liberal applications of our petro-chemical economics.

  13. on 11 May 2012 at 6:16 pmSue Donaldson

    I see you carry Manzanillo sea salt but I am looking for Colima flor de sel that is sold under the Aires de Campo organic co-operative producers label in Mexico. I can’t seem to find sources in the PNW of the U.S. or in BC, Canada that carry this particular flor de sel that I like very much. Do you have any plans to carry other Mexican flor de sels such as this one or have an idea where I might source Aires de Campo flor de sel from Colima?

  14. on 26 May 2012 at 11:08 pmthinkalittlenotalwaysblackandwhite

    Hey good evening I wanted to chime in because I have a very unique perspective on things . . Ever since I got into avoiding gmo foods, supporting farms that raise their animals humanely for the meat and dairy I consume, buying organic, and such, I always bought sea salt. However recently, I realized the very things people were thinking when they came to this site. Things such as, jeezus if sea salt is just evaporated ocean water, maybe in prehistoric times would this be ok, but nowadays will all of the nasty ocean water what are we thinking ?!!?!

    I just wanted to throw out there just because pure sodium chloride isn’t natural, I don’t always believe we have to go ape-sh*t (excuse my french) and claim it’s poison . . What if our bodies see it as pure salt (which it is) ok, big deal, so the body takes it from there and uses what it can from it.
    I am not a scientist and I don’t know anything about salt, but I don’t always think something has to be totally “natural” for our bodies to work with it. That is what’s so cool about science, now we can take something like salt, get rid of all of the nasty ocean water contaminants, and get down to the “purest” of “pure” sodium chloride . .

    Just wanted to throw out my 2 cents to you guys, sometimes everything isn’t black and white, our bodies will take what we can from the salt, absorb what energy we can from it, and then pass it thru . . .

    I would gladly like to hear any knowledge (always up for strengthening that brain power!) and information about why table salt is harmful (besides the additives), as I am trying to find an additive-free table salt.. When I found out table salt comes from salt mines, to me that is more pure than ocean water . .
    Are there any table salts from “clean” “eco-friendly” salt mines that do not have any additives, just the pure salt mine salt?!?!?!

    Thank you guys have a good one :)

  15. on 09 Jul 2012 at 4:00 pmMark Bitterman

    @Sue – I don’t know of a place to find that salt in the United States. Our Manzanillo salt is made from a neighboring saltmaker, using the same waters using a possibly better, hand harvested process.

  16. on 12 Jan 2013 at 3:32 pmSara

    To the folks whose concern is contamination by biological agents such as bird poop, etc., remember that pure crystalline salt is used as a very effective anti-microbial. It kills living cells by desiccating them, which is the same mechanism through which bleach is effective. It does the same thing to all living matter, which is why salt curing is so effective in preserving meats. Anything in bird poop (other than chemical agents) that would be a threat to humans would be killed off by the crystalline/concentrated salt itself. Basic biology.

  17. on 17 Oct 2013 at 3:23 amElisa C

    Thank you for the info

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