[Slraep]

It's a question that has been bouncing around my head for a while.

Waters around the globe are increasingly being contaminated with heavy metals, mercury being a biggie.

Pearl molluscs(Akoya especially) filter feed and so ingest large amounts of pollutants which accumulate in their soft bodies and in their shells. Akoya molluscs in particular have been used for pollution monitoring. How does this affect the pearl? If Akoya shells have shown high levels of mercury, lead, cadmium and thullium(just to name a few), it must follow that the pearl is contaminated too. Are there any consequences to wearing pearls? How do the affected pearls affect us?!? I wonder. Some people are super sensitive to heavy metals--especially mercury. Anyway, heavy metals are bad news for anybody.

Any thoughts?

Slraep

[knotty panda]

Interesting question indeed especially with so many people placing the pearls in their mouth to see if they're real.

Seafood is closely monitored and would present the same contaminant levels as mollusks. The mollusk by-products would present a lesser amount of contamination. Thallium and cadmium are rapidly decaying contaminants and would dissipate before shells and pearls reach you. Mercury and lead decay at a much slower rate. How much detective work does the Canadian government do to uncover such contaminants? I heard a report on the news this evening that they have found lead contamination in baby bibs imported from China. I don’t know who thought to check baby bibs for contamination, but God bless them! With so many scandalous things happening with Chinese imports, I think they’re scrutinizing every product imported from China. You may have an answer to your question quickly.

[Raisondetre]

Another interesting point is that Chinese believe in the use of powdered pearl for medicinal/beauty purposes. The levels of lead would probably be more significant if the powder were ingested.

[Slraep]

Originally Posted by knotty panda

Seafood is closely monitored and would present the same contaminant levels as mollusks.

No, not necessarily. That's why serious pollution monitoring uses the akoya oyster. The rate at which the mollusc filters water for nutrients is very high.

The mollusk by-products would present a lesser amount of contamination. Thallium and cadmium are rapidly decaying contaminants and would dissipate before shells and pearls reach you. Mercury and lead decay at a much slower rate.

Mollusc by products would have the same amounts of contamination.
The oysters are filtering thulium and cadmium at a constant rate so any decay would not apply if you were ingesting them(no thanks for me) and pearl handlers would be at risk for low to moderate toxicity. Thulium has a half life of 1.92 years, which is not a fast enough decay for contaminated akoya pearl necklaces, in my opinion, anyway.

How much detective work does the Canadian government do to uncover such contaminants?

We do not grow akoya oysters in Canada and we do not have a saltwater pearl industry, so studies were done where akoya oysters normally thrive.

Well. I must admit., my question is just a disguise for thought provocation.

Slraep

[Slraep]

Originally Posted by Raisondetre

Another interesting point is that Chinese believe in the use of powdered pearl for medicinal/beauty purposes. The levels of lead would probably be more significant if the powder were ingested.

Hi Raisondetre,

Scary isn't it !! Get your daily dose of calcium along with a whole slew of contaminants. Even many brands of "coral calcium" coming out of Japan were shown to be contaminated. Sad.

Slraep

[CortezPearls]

Hmmm...very interesting question. I will try to find an answer...have some articles about the use of bivalves as pollutant bio-indicators, but those I remember reading have always concerned themselves with the use of the oyster's flesh and never the shell. This could be due to the fact that it is much easier to produce a "pulp" from flesh (for analysis) than from shell, but maybe the natural biomineralization of metals in the shell does not accomodate these pollutants. Porphyrins are metallo-proteins that are a part in natural pearl coloring, but I have never heard or read about a mercury or cadmium based porphyrin, most are iron and copper based.

My first guess is that it is not an issue...let me see if I can find more information.

[Slraep]

Hi Douglas,

I would very much appreciate any info you can find and share.

I only know a bit about the lead contamination. If an akoya oyster is purposefully exposed to high doses of lead for a short period, there seems to be no significant contamination. The bivalve probably detects the lead and goes into anaerobic mode for a while. On the other hand, if the exposure is natural and of a prolonged duration then most of it can be detected in the shell. High levels of lead for prolonged periods will impead biomineralization. The molluscs will not grow. Low levels of lead for prolonged periods will actually do the opposite and speed up shell growth.

I know of potassium, and magnesium as a metallo-protein, affecting the colour of nacre to a certain degree, but I have no idea if any of the said contaminants are porphyrin based either.

Mercury contamination seems to affect a mollusc's immune response. Thulium seems to come from illegally dumped mercury. If I'm not mistaken, thulium is added to mercury and used in heavy duty thermometers in northern weather stations. Someone is either illegally recycling the mercury from these or dumping the used material into the ocean. Probably the former because certain dental amalgam mixtures have been found to contain traces of thulium. There really is no limit to what man will do for a buck.

Slraep

[pernula]

Some mercury may also come from coal power plant. Mercury is present in coal, and when coal is burnt to generate power, the mercury is released into the air and eventually deposited to terrestrial and aquatic systems, including the ocean. Exactly how much is hard to determine and controversial. This is just one of the many references.

http://www.powerthefuture.com/public...ts_mercury.pdf

pernula

[Slraep]

Originally Posted by pernula

Some mercury may also come from coal power plant. Mercury is present in coal, and when coal is burnt to generate power, the mercury is released into the air and eventually deposited to terrestrial and aquatic systems, including the ocean. Exactly how much is hard to determine and controversial. This is just one of the many references.

Choke, gasp. No wonder cases of asthma are on a steep rise. Cough.

Slraep

[Slraep]

Douglas, do you know if any of the metals could possibly be crystal binding as opposed to organic protein binding, or both?

Slraep

[knotty panda]

I was confused on your metals. You were talking Thulium, I was talking Thallium. Close but no cigar. Both metals, both toxic, but you're right, Thulium decays much slower than Thallium. Lead and mercury are both detected in background levels so there is no completely escaping them.

There's tons of information on both NIOSH's website and the CDC on lead and mercury.

[purepearls]

There are massive recalls on toys (including Sesame Street toys) that have been manufactured in China and have excessive lead in the paint. There has also been growing concern that this lead paint is being used on painted jewelry as well. This does not concern pearls but it does effect many of you whom love jewelry!

[Slraep]

Originally Posted by purepearls

There has also been growing concern that this lead paint is being used on painted jewelry as well. This does not concern pearls but it does effect many of you whom love jewelry!

That's true and not only the paint but some of the metal used in costume jewelry coming from China also has lead in it, especially if you can bend it quite easily.

Slraep

[CortezPearls]

Originally Posted by Slraep

Douglas, do you know if any of the metals could possibly be crystal binding as opposed to organic protein binding, or both?

Slraep

Sorry, my feeble knowledge on biomineralization does not allow me to draw any conclussions on this subject. Have read dozens of scientific articles on the subject, but have not found a single one that will give me any additional insight...most articles are about the use of bivalve fleshy tissue as a bioindicator, none focus on the shell itself.

On our experience farming pearl oysters I can only say that weakened/sick animals will usually display a more yellow (some would say "golden") coloration, because they deposit less nacre and a bit more protein. One of the reasons I think why Japanese Akoya are yellow is due to water pollution...I guess the poor creatures can barely survive under those conditions and produce "sickly pearls".

But I haven't found any real lead (not the metal Lead).

I need more time, sorry.

[CortezPearls]

PbSO4 is the common soluble form for lead, the one that causes most common lead toxicity. I don't think this form would be present in salt-water...NaCl (salt) would react with it to form PbCl2 (have to check this, my inorganic chemistry is bad these days) and it is an insoluble compound, would precipitate...but fresh water would be a different thing.

Mercury: nothing can save us. Regardless of salt or fresh, cold or warm, waters...