The Stanley Tumbler Stainless Steel Cup is the most popular reusable stainless steel water bottle in the United States, but lately there’s been lots worries about it containing dangerous levels of lead. Stanley has issued a statement saying they do contain lead in the sealing dot which is inaccessible to the consumer, but what about the rest of the cup?
After viewing many consumers using common home lead tests and finding something in the Stanley, there’s been another uptick of concern. Does the Stanley pose a risk of lead poisoning to it’s users? This is an important question to answer, so Mamavation decided to send the Stanley to an EPA-certified laboratory to find out once and for all if there is any lead or cadmium inside the Stanley Cup that can be leached out with normal everyday use.
You’ve trusted Mamavation to bring you topics like safest cookware without PFAS “forever chemicals,” best air purifiers to clean your indoor air and safest air fryers now join us for another consumer study this time on the Stanley Tumbler tested with acid for lead and cadmium.
Disclosure: This post was medically reviewed by Sondra Strand, RN, BSN, PHN. This post also contains affiliate links, some of which are to Amazon. Mamavation paid for this testing on our own and did not receive any money from other parties for this purpose. We will use any affiliate money received from this post to pay ourselves back for this testing and fund other consumer investigations in the future.
You can also give a tax-deductible donation to our consumer studies here through Environmental Health Sciences. Thank you for supporting Mamavation!
Stanley Cup, Among Other Reusable Stainless Steel Water Bottles, Have Lead Sealing Dots
The 18/8 stainless steel Stanley Cup does contain a lead sealing dot, but so do most other 18/8 stainless steel water bottles. The reason why this is allowed is because it’s not accessible to the consumer under normal everyday use. In fact, you would have to break the bottle to be exposed to the lead on the outside bottom portion of the cup. Here’s information about the lead sealing dot coming straight from the Stanley website:
“Our manufacturing process currently employs the use of an industry standard pellet to seal the vacuum insulation at the base of our products; the sealing material includes some lead. Once sealed, this area is covered with a durable stainless steel layer, making it inaccessible to consumers.
Rest assured that no lead is present on the surface of any Stanley product that comes into contact with the consumer nor the contents of the product. In the rare occurrence the base cap of a product comes off due to ordinary use and exposes this seal, it is eligible for our Lifetime Warranty, available here: www.stanley1913.com/pages/contact-warranty.”
Lead Sealing Dot Confirmed by Eric Ritter From DetectLead.com
We’ve recently become a big fan of the work of Eric Ritter, who is with Scitus Lab Products and DetectLead.com. He’s been making low-cost lead testing kits for consumers since 2019. A few weeks ago, Eric decided to cut the Stanley in half with a chop saw to take a look at where the lead dot is located. Then he used his XRF machine to ascertain how much lead was located inside the unit. We think this video is very helpful to show you where the lead is located.
Results From Mamavation’s EPA-Certified Laboratory
Mamavation sent the Stanley to an EPA-certified laboratory to have it filled with acid for 24 hours and then have the acid tested for lead and cadmium. This type of testing alerts consumers as to how much lead and cadmium would come out of the cup over years of normal use. But we decided to alter this testing and have the lab use a far stronger type of acid, so that we could mimic something like coffee or orange juice use as well.
The Method Used to Test the Stanley Cup for Lead and Cadmium
The stainless steel surface inside the Stanley tumbler was first rinsed thoroughly with ultrapure water to remove superficial contamination. This was roughly five rinses of 100 mL of ultrapure water. Then 100 mL of a 1% nitric acid solution was transferred into the tumbler. The acid solution was left to sit in the thermos for 24 hours. Then the nitric acid was transferred to a centrifuge tube, and then analyzed by ICP-MS.
Lead and Cadmium Results From Our EPA-Certified Lab
Lead results — The concentration of lead measured in this solution was 2.1470 ug/L (i.e., ppb), which is equivalent to 0.2147 ug per unit (i.e., 2.1470 ug/L x 0.100 L), where 1 unit = 1 thermos. 0.21470 ug is the value calculated after accounting for the volume (i.e., 100 mL = 0.1 L) of 1% nitric acid added to the thermos. The reported value is in units of ug/L.
- The calculation is as follows: 2.1470 ug/L x 0.1 L = 0.21470 ug
Cadmium results — The cadmium results were non-detect.
Prop 65 Compliance for California
The California Prop 65 requirements for lead and cadmium are very particular and are as follows:
- The Lead limit must yield less than 100 mg/kg
- The Cadmium must yield less than 300 mg/kg
- Lead results for Stanley: 0.2147 ug = 0.0002147 mg
- Cadmium results for Stanley: Non-detect
The CA Prop 65 requirements for lead are in units of mg/kg. To get units of mg/kg, we would need to take the mass of lead per unit (0.0002147 mg) and divide by the mass of the stainless steel surface. There is not a straightforward way to acquire this mass, but it doesn’t really matter because it’s safe to say that 0.0002147 mg divided by the mass of the stainless steel surface will be orders of magnitude below the limits of Prop 65 for California.
Acid Used by Mamavation’s Lab — Nitric Acid vs. Acetic Acid
Mamavation’s lab used 100 mL of a 1% nitric acid solution to acid bath the Stanley Thermos. This acid was far more acidic than the acid that is required by Prop 65 testing. The CA Prop 65 mandates 4% Glacial Acetic Acid in a 24-hour test for leaching metals.
In other words, we didn’t use something as light as acetic acid (vinegar) mandated to do the testing, we used an acid that would actually burn your skin if it was applied. Therefore, it’s our opinion that the testing we did of the Stanley was far stronger and had the capability of leaching far more lead than what would be required of State of California.
Outcome of the Stanley Lead and Cadmium Study and Additional Questions Answered
Q: So what does this mean?
A: The lead and cadmium leached out of the Stanley after the acid bath it received at the lab were far below (thus safer) than what would be acceptable by the State of California and Prop 65 standards, which are some of the strictest in world for lead. Therefore, with normal use of the Stanley, there is no lead or cadmium exposure that is concerning.
Q: What about the viral video using lead testers finding lead in the Stanley?
A: We did see a viral video posted a few weeks back that used generic chemical lead testers finding that the Stanley caused a chemical reaction, which under some circumstances would mean lead is present. However, those chemical stick tests aren’t really made to test stainless steel. They are made to ascertain whether lead is present inside things like paint or porcelain plates.
In order to ensure that chemical test was really working correctly around the stainless steel, you would need to dip it one more time in lemon juice and see if it still stayed discolored. The person who utilized those tests may not have been aware of this trick, so that was not done.
Unfortunately, this video has many women concerned about the lead contamination inside the Stanley. But as you can see, when the Stanley is sent to an EPA-certified lab and acid bath tested, it does not pose a lead or cadmium threat.
Q: Is there danger of the lead sealing dot leaching through the Stanley and contaminating my water?
A: Online I saw many people claiming that the lead sealing dot would leach into the water over time. I would say this isn’t a very likely scenario based on what was found when Eric Ritter opened up the Stanley. Please go back and look at that video. You’ll clearly see that there is a big gap between that sealing dot and the stainless steel that holds the water. I’m glad we can put that to rest for you. (See Instagram video from above.)
Q: What would happen if my Stanley broke and the sealing dot was exposed?
A: In the case of your Stanley breaking exposing the sealing dot, yes you could be exposed that way to a dangerous amount of lead. In this situation, we would recommend either you tossing the Stanley OR contacting them for a refund of the product.
The Stanley offers a lifetime warranty on their product and you can find more information on getting that refund. Here is that information in Stanley’s own words: “In the rare occurrence the base cap of a product comes off due to ordinary use and exposes this seal, it is eligible for our Lifetime Warranty, available here: www.stanley1913.com/pages/contact-warranty.”
Q: Is the Stanley putting my children in danger of being lead exposed?
A: Based on our study of this product and what Eric Ritter found when he pulled it apart, we do not believe that the Stanley is problematic. You would have to damage it quite a bit during everyday use, which is unlikely.
However, Mamavation does NOT like their polymer based straws. We are more concerned about the microplastics and plastic additives that may leach out of the product over time.
What’s the point of drinking out of a stainless steel tumbler if you are going to use a plastic or silicone based straw? So we do have a work-around for you so you don’t have to toss your Stanley. There are stainless steel and glass straws sold on Amazon that can replace the straws in your Stanley that are found here:
Q: Do you work for Stanley or have you ever done business with Stanley?
A: Mamavation has never worked with Stanley before. We have no financial ties to this company. Therefore, we are a true independent third party simply trying to answer the questions we’ve been asked by our community by using lab testing.
Q: Are there other stainless steel reusable water bottles that do not contain a lead sealing dot?
A: Yes, there are other stainless steel water bottles that do not contain a lead sealing dot. One such company is Pura and we spoke to their Founder the other day to confirm they use another type of sealant that is not made from lead. Pura has offered our community a discount on their products and you are welcome to purchase using our discount. We will use that money to pay ourselves back for the testing and fund other projects going forward to answer your questions.
• Pura Insulated Stainless Steel 28 oz Sports Water Bottle (18/8 stainless steel with pop-off top and no polymer straw)
• Pura Insulated Stainless Steel 22 oz Sports Water Bottle (18/8 stainless steel with pop-off top and no polymer straw)
• Pura Insulated Stainless Steel 16 oz Sports Water Bottle (18/8 stainless steel with pop-off top and no polymer straw)
Additional Consumer Studies Led by Mamavation
Here is a list of other consumer studies that involved sending products to an EPA-certified lab and reporting back on PFAS “forever chemicals,” heavy metals, or microplastics:
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Beauty and Personal Care Product Testing |
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Food and Beverages Testing |
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Supplement Testing |
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Menstrual Products Testing |
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Clothing Testing |
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Food Packaging and Parchment Paper Testing |
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Baby and Children PFAS Testing |
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Computers, Phones and Office Testing |
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Cleaning and Laundry Testing |
About the Author
Leah Segedie is the President and Founder of Mamavation.com. Mamavation produces award-winning content and independent consumer studies examining the intersection of endocrine-disrupting chemicals (EDCs) and everyday products brought into American households. She’s been referred to by many as “the real FDA.”
Since 2008, Mamavation has been helping everyday moms navigate the grocery store by commissioning consumer studies on food, beverages, personal care products and other such products and thus democratizing science and testing for everyone.
