Kirkland Signature Pure Sea Salt, fine grain, 30 oz

1. Ingredients 25% of the rating 5 of 5

   Costco’s page lists one ingredient, sea salt, with no anti-caking agent, dextrose or added iodide.

2. Independent testing 35% of the rating 3 of 5

   One independent lab found lead and cadmium not detected, but it was one sample, named “Kirkland Sea Salt Fine Grain” with no size, and microplastics could not be identified in any salt.

3. Packaging 10% of the rating 2 of 5

   A clear plastic bottle with a black plastic flip-top cap, per Costco’s photo. The plastic type and any liner are not stated. The salt is dry, and we found no study of plastic moving from a salt container into salt.

4. Trust 15% of the rating 3 of 5

   No recalls, Prop 65 notices or FDA actions found for the salt. The producer is not named and Costco posts no test results of its own.

5. Value 15% of the rating 5 of 5

   $3.99 for 30 oz online ($2.13 a pound) and $3.29 in the warehouse we checked ($1.75 a pound), the cheapest clean salt here.

The rating, 3.7 of 5, is the weighted average of these scores. See how we rank salt & minerals and our standard.

1. Sea salt

• Independent Mamavation (EPA-certified lab, not named; the site earns affiliate income on Amazon sales and shares discount codes with some brands) May 2026

  Tested “Kirkland Sea Salt Fine Grain” for metals: aluminum 1.48 ppm, arsenic below the reporting limit, cadmium not detected, mercury below the reporting limit, lead not detected. Lead was found in 96% of the first 23 salts it tested. Its FTIR imaging could not conclusively identify microplastics in any salt. Open ↗ (opens in a new tab)

Does it contain lead or other heavy metals?

Not that Mamavation’s lab (opens in a new tab) could measure: lead and cadmium were not detected, and arsenic and mercury were below its reporting limits. That puts it in Mamavation’s lowest-metals group, where most of the salts it tested had some lead and Kirkland’s pink salt had 61 ppb. It is one sample, and we found no second lab’s result.

Is there plastic in sea salt?

It can be. A 2018 study (opens in a new tab) of 39 salt brands found 0 to 1,674 particles per kilogram in sea salts (one outlier had 13,629), with higher counts in salts from Asia. Mamavation’s FTIR imaging could not conclusively identify microplastics in any salt it tested, so it could neither confirm nor rule them out. Nobody has published a count for this salt. See our microplastics guide.

Is Kirkland’s pink salt the same?

No. Kirkland’s fine-grain pink salt (5 lb) is a different product, and Mamavation found 61 ppb of lead in it. This page is about the white sea salt.

Where does it come from, and who makes it?

Costco’s page says it is harvested from the waters off Australia and carries the Orthodox Union kosher mark, and gives no producer, harvest site or test results. Kirkland Signature is Costco’s own label, so the supplier can change.

Is it iodized, and does that matter?

No iodide is listed, only sea salt, and the bottle label in Costco’s photo says “This salt does not supply iodide, a necessary nutrient.” Salt is a main source of iodine for some people, and sea salt is not a reliable one: see our iodine guide and sea salt guide.

Any recalls, lawsuits or warnings?

None for this salt. California’s Prop 65 notice search lists 192 notices naming Costco, and none names a salt (a search for “Kirkland” returns 42 notices, all for Kirkland’s, a home-goods chain). openFDA’s food enforcement search shows no recall of a Costco or Kirkland Signature salt, searched 3 Nov 2026.

• One ingredient. Costco’s page lists sea salt only, with no anti-caking agent, dextrose or added iodide, and calls it fine grain and kosher (Circle U).
• An independent lab found no lead or cadmium in a Kirkland fine sea salt, arsenic and mercury below its reporting limits, and aluminum at 1.48 ppm, in Mamavation’s lowest-metals group (updated May 2026).
• It is the cheapest clean salt we list: $3.99 for 30 oz online, $2.13 a pound, and $1.75 a pound in the warehouse we checked.
• No recall, Prop 65 notice or FDA action over a salt was found for Costco or its Kirkland Signature label.

• One independent test of one sample, for a product named without a size, and Costco posts no results of its own. We could not confirm the tested item was this 30 oz bottle.
• The bottle is clear plastic with a black plastic flip-top cap in Costco’s photo, and the plastic type and any liner are not stated.
• Costco names no producer or harvest site, only waters off Australia, and since the Kirkland label is Costco’s own the supplier can change.
• It is not iodized (the label says it “does not supply iodide”), nobody has published a microplastics count for it, and only Costco sells it, so you need a membership.

1. Costco: Kirkland Signature Pure Sea Salt, 30 oz (item 384732). Maker’s page. $3.99 online (the page data marked it out of stock for delivery on 2026-11-03) and $3.29 in the Cumberland Mall, Georgia warehouse on 2026-11-02; ingredient list, origin line, 850 g net weight and bottle photo. Open ↗ (opens in a new tab)
2. Mamavation: sea salt and Himalayan salt tested for heavy metals and microplastics. Test report. 23 salts at first, more added since; Kirkland’s sea salt and pink salt results marked updated May 2026. The site earns affiliate income. Open ↗ (opens in a new tab)
3. Kim and colleagues: microplastics in commercial food-grade salts (Environmental Science and Technology, 2018). Test report. PMID 30285421. Tested 39 salt brands, 28 of them sea salts from 16 countries or regions; this product is not named. Open ↗ (opens in a new tab)
4. California Attorney General: Prop 65 60-day notice search. Certifier or regulator listing. Searched by alleged violator for “Costco” on 2026-11-03, reading all 192 notices: none names a salt. A search for “Kirkland” returns 42 notices, all for Kirkland’s, a home-goods chain. Open ↗ (opens in a new tab)
5. openFDA: food enforcement reports. Certifier or regulator listing. Searched 2026-11-02 and 2026-11-03 for Costco and Kirkland salt products: no recall of a salt. The only Costco food report that mentions salt is a 2012 smoked salmon recall. Open ↗ (opens in a new tab)

• Diamond Crystal Kosher Salt (3 lb box) Plain salt in a paperboard box, clean at two independent labs, about $4 a pound.

• Minerals, Sodium, and What to Look For Article How sea salt differs from refined table salt, why iodine still matters, what the actual sodium-and-health evidence says, and how to choose a salt that supports rather than undermines your diet
• Thyroid Essential Article Why iodine deficiency is still widespread, how the thyroid depends on it, and practical ways to optimize intake
• Reducing Your Microplastic Exposure Article Practical steps to minimize microplastic intake from water, food, and everyday products