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How worried should you be about lead in your Stanley cup?

The water tumblers are going viral now as people realize there’s a lead pellet concealed in the product’s base, but Northeastern experts say this is not the biggest concern when it comes to lead exposure.

A white stanley cup on a blue background lit up by studio photo lights.
Photo by Matthew Modoono/Northeastern University

Stanley cups, a brand of insulated tumblers, are the latest “it” water bottle, following in the footsteps of Nalgene and Hydro Flask before it.

Their popularity prompted pandemonium at Targets over a chance to get the brand’s limited-edition Valentine’s Day collection and a skit on “Saturday Night Live” poked fun at the craze. Youths aren’t immune either: Parents have taken to social media saying their kids have been bullied for not having a Stanley cup.

But now, these massive handled cups are gaining traction for another reason: Consumers are concerned about the risk of lead poisoning from a lead pellet concealed in the base of the mugs.

Users on social media raised the alarm about the presence of lead in the tumblers over the last few weeks. These claims gained traction as some people began using home lead-testing kits on their mugs to suss out the risk.


If you’re getting a positive lead test from a perfectly intact Stanley, you may want to test your drinking water. #StanleyCup #StanleyTumbler #StanleyLeadTest #LeadTesting #News

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So, are Stanley cups safe? Though the practice of using lead as a whole poses some risks, the products shouldn’t cause lead poisoning unless the bottom comes off and exposes the lead pellet, says Kimberly Garrett, an environmental toxicologist and a postdoctoral research associate working at Northeastern University’s PFAS Project lab.

“From what I understand, that’s an industry standard,” Garrett says of the lead pellet. “Just because it’s common doesn’t mean it’s safe, but it is completely insulated within the mug. With regular use, it’s not supposed to pose any risk. However, I have read some reports of the bottom falling off in a very specific way and then exposing that lead. It’s a situation where if the structural integrity is maintained, it’s not supposed to be a risk to people.”

The company says the lead pellet is used “to seal the vacuum insulation at the base” of mugs and that the pellet is covered by a layer of stainless steel. It says the likelihood of the cap coming off due to “ordinary use” is “rare.” 

“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,” Stanley writes on its site.

However, the Stanley cup is not the number one thing people need to worry about when it comes to lead poisoning, says Neil Maniar, director of the master of public health in urban health program at Northeastern University and professor of the practice in health sciences. Lead can be found in the pipes and paint in older homes, as well as in cosmetics, toys, jewelry and even dishware. 

“Lead poisoning is harmful, but when we talk about lead poisoning, oftentimes we’re talking about persistent or chronic exposure to lead,” Maniar says. “If a cup like this is damaged and someone continues to use it and there is contact between the water and the lead, could that be harmful? Possibly, but I think there are far more significant sources of lead poisoning that we need to be concerned about, especially when we think about other types of environmental exposures or other types of potential household exposures.”

Garrett says lead was once commonly used in pipes and paint, posing a high risk of exposure for people who live in homes that were made while these types of products were still in use. Lead is still often used in industrial practices because it’s cheap and useful, making manufacturers less inclined to find safe alternatives, especially given a lack of regulations in some areas when it comes to lead use.

“There’s a lot of focus on the Stanley cup because it’s such a viral thing,” Maniar says. “Everyone’s talking about it … (but) there are dozens of other things that we should be worrying about in terms of potential sources of lead.”

This might be why some people’s at-home lead tests are coming back positive when using them on their Stanley cup, Garrett says. The lead levels might be from the pipes the water is coming from, not the mug.

“I don’t know how the lead from the little insert would get into the water,” Garrett says. “I have seen claims that people have tested the inside of the water bottle and it’s come back positive. … Before saying for certain it’s the water bottle, I would test their drinking water because it could be that they have a lead problem in their drinking water because those tend to have higher concentrations than an incidental lead exposure.”

Exposure to lead is toxic to many systems in the body. Garrett says long-term lead exposure can lead to neuropathy, renal failure and cognitive problems.

Vulnerable populations like babies and pregnant people are especially susceptible to its negative health side effects. Lead poisoning can lead to delayed cognitive development in children.

“It can really impair the development of the brain,” Garrett says.

Garrett added that people with calcium deficiencies are also especially susceptible to lead poisoning.

“If someone is low in calcium, (their body) will take up that lead instead of taking up calcium or in addition to calcium,” Garrett says. “It basically can mimic calcium in your body. It’s really persistent that way.”

The lead in these products also poses a threat to the environment, Garrett says. When these products are disposed of, the lead can seep into the soil or be consumed by wildlife.

Garrett encouraged people not to dispose of their mugs if it seems structurally sound and not at risk for exposing the lead pellet. If the bottom does fall off, Stanley says it will take back the mug under its lifetime warranty.

The larger concern is the age of Stanley cup users: These trendy tumblers are becoming a necessity among the elementary school crowd who might be more prone to dropping them on the playground and breaking the bottom cap. Garrett cautioned parents to consider this before buying one for their child.

“I wouldn’t go out and buy a child a Stanley mug now knowing that this is a risk,” Garrett says. “If you already bought one for your kid and they are attached to it, check it when they come home from school. Teach kids to check it for themselves. This can be a really cool learning opportunity for kids to learn about environmental health and how the things they encounter every day and the things they use can be harmful. But they can learn about why and how to avoid that.”