I get these questions a lot!
“Do sea shells have Lead?”
“What about Cadmium and Mercury?”
“Are they safe for my kids to play with?”
While the food category “shellfish” (like scallops, mussels, clams and shrimp) are notoriously high in Lead, their shells are another matter. For context however, it is important to know that food toxicity is measured in parts per billion (ppb) whereas consumer goods (and toys and other items that might normally be used by children) are measured for toxicity in parts per million (ppm) (there are 1,000 ppb in 1 ppm) … so, while an item might test as “negative” from the context of being used as a handled item (“consumer good”) — the most applicable context used for a shell that a child might collect or play with — those test results don’t have any bearing on the potential for toxicity for that same animal (clam vs. clam shell) when consumed as a food. Food and beverage items intended for human consumption are usually considered toxic (from a Lead perspective at least) if they are positive for anything in the range of 5 ppb to 100 ppb and up- depending on the product (this is a level far below the limit of detection of an XRF instrument setup to test for Lead in consumer goods – measured in ppm.)
I have tested quite a few shells (of different sizes, from different animals and from different parts of the world) and never found one to have XRF detectable levels of heavy metals. This does not mean that it is not theoretically possible for sea shells to have unsafe levels of heavy metals, it is – but I have not found this to be a problem when looking at intact shells being used as a play thing for young children. In fact, I love the idea of children playing with natural items like shells, rocks and sticks – and I always encourage that type of imaginative and creative play.
To see the exact XRF test results for the shell pictured in this post, please scroll down. I am posting several different posts with XRF test results for shells, however other than the XRF readings each post otherwise has the same text.
While the shell pictured is positive for some metals at trace levels, it is negative for Lead, Mercury, Cadmium, Antimony and Arsenic – within the limits of detection of the XRF instrument, when tested for a minimum of 60 seconds. Test results are science-based, and replicable; each test was repeated multiple times to confirm the results.
While overall I have no concern for toxicants found in seashells (especially in the context of children playing with them), I do want to clearly state the following the exception: If shells are from bottom-feeding filter animals (which most shells are) then they likely have at least some heavy metals (even if it is below the level of detection for any XRF instrument.)
As a result, there are documented cases (including one that has been widely-circulated in social media over the past few years) in which an artist or craftsman grinds or pulverizes shells as part of their work and has been poisoned as a result of the cumulative exposure to all that dust. As with any grinding and sanding or drilling (no matter what the item is that is being worked on – wood, stone, shell, metal, etc.), proper masks and protections should be worn — not only because your lungs are easily damaged from any airborne particulates, but also to protect your health in the off-chance that the items you are working with may contain some amount (trace or otherwise) of heavy metals – including Lead. Even trace levels can be very toxic when an item is sanded or ground [or even cut, drilled or otherwise machined], producing micro-dust that can be inhaled or ingested.
One set of XRF test results for the clam shells pictured here
Test done on the outside of the shell:
- Lead (Pb): Non-Detect (negative) – (and at least below 22 ppm)
- Cadmium (Cd): Non-Detect (negative) – (and at least below 17 ppm)
- Mercury (Hg): Non-Detect (negative) – (and at least below 36 ppm)
- Antimony (Sb): Non-Detect (negative) – (and at least below 40 ppm)
Metals detected (confirmed to be present) on the above test:
- Bromine (Br): 7 +/- 3 ppm
- Titanium (Ti): 240 +/- 80 ppm
- Iron (Fe): 2,888 +/- 363 ppm
As always, thank you for reading and for sharing my posts.
Please let me know if you have any questions.