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Spotlight: Tracking Methylmercury, a Toxic Substance in Natural Waters

Foreground: Lake. Background: Trees.
Credit: J. Stoughton/NIST

Mercury — the only metal that exists in liquid form at room temperature — may move like water, but its effect on the environment certainly isn’t replenishing. We’re helping researchers, industry and environmental regulators track it.

This mercury isn’t the pure element on your periodic table. Once it enters the atmosphere via industrial processes and falls with the rain into our waters, microorganisms in the environment convert it into a biologically toxic form (methylmercury, or MeHg). 

The substance can accumulate and magnify as it’s absorbed into the food chain, which means:

A tiny organism with MeHg gets eaten by a small fish with MeHg ...

Which gets eaten by a bigger fish with MeHg ...

Which gets eaten by an even bigger fish with MeHg ...

Which gets eaten by a top predator fish with MeHg ...

Which gets eaten by a person. 

This hypothetical chain has five creatures, each one contributing to the next one’s level of the hazardous mercury form, before it reaches the person. All of that MeHg ends up in the person’s system. And just think about the accumulation if the person eats predator fish every day.

Environmental organizations use specialized instruments to measure amounts of mercury in natural waters, but how do they know their tools are working properly?

Cue NIST’s Standard Reference Material (SRM) 1641e, Mercury in Water.

SRM 1641e is made up of 10 ampuls, each containing trace amounts of mercury in about 10 milliliters of liquid. Along with the samples, NIST provides a detailed document of their characterizations. Researchers can use their measurement instruments to analyze the samples, and, if the results are the same as ours, they can rest assured that their tools are accurate.

NIST sells more than 1,000 different types of SRMs — including everything from gold nanoparticles to peanut butter — to analytical laboratories, industrial leaders and federal partners. Get the background on our SRM program.

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Released August 16, 2021, Updated August 23, 2021