• Geoduck clams are an important U.S. food export and are critical to local economies on the Washington state and Alaskan coasts.
  
• To ensure that these clams and other shellfish are safe to eat, they must be tested for toxic elements and compounds, including inorganic arsenic.
• NIST researchers have developed a standard reference material that will support more accurate measurements of inorganic arsenic in geoduck clams and other shellfish.

Even if you are a big fan of scallops, oysters and other shellfish, you may not have heard of the geoduck clam. But these outsized mollusks are an important food export to Asia and vital to coastal economies in Washington state and Alaska. Divers from these states harvested more than $60 million worth of them in 2023, according to the National Oceanic and Atmospheric Administration (NOAA).

To promote confidence in their food products, these states must test geoduck clams and other shellfish for toxic elements and compounds, including inorganic arsenic, a known carcinogen.

To help ensure accurate measurements, researchers at the National Institute of Standards and Technology (NIST) have developed a standard reference material (SRM) made of geoduck tissue containing very carefully measured amounts of inorganic arsenic. This material will help states monitor inorganic arsenic levels in their geoduck exports. It will also help ensure the food safety of geoduck clams and other shellfish sold in the U.S.

“Many marine organisms absorb arsenic because it is naturally present in the ocean environment,” said NIST biologist Colleen Bryan Sallee, who led the development of the material. “This material will help ensure that inorganic arsenic is accurately measured in shellfish for determining food safety.” 

Previously, geoduck clams were tested for total arsenic, which includes the element in both its organic and inorganic forms. But the inorganic form is considered more toxic, and the new SRM will help labs accurately measure that form specifically.

SRM 2983: Inorganics in Geoduck Clam Tissue (Panopea generosa) consists of one jar of frozen geoduck clam tissue, along with a document listing the measured amounts of organic and inorganic arsenic, with uncertainty values for each.

Seafood testing laboratories and research organizations can ensure the accuracy of their measurements by running a small sample of the SRM through their instruments. If their results match the certified values from NIST to within a specified uncertainty, then they can have confidence in their measurement methods. If not, they’ll know they need to adjust their methods. 

To create this new material, researchers shucked, cleaned and diced geoduck clams, froze them in liquid nitrogen, and ground the frozen tissue into a fine powder. They used an analytical technique called inductively coupled plasma mass spectrometry to measure the arsenic amounts in the material.

NIST produces more than a thousand SRMs that promote public health and safety and support U.S industry. These materials help ensure accurate measurements in industries ranging from food (peanut butter and infant formula) to health care (cholesterol in blood serum) to manufacturing (carbon steel) and many more.

NIST researchers collaborated on this project with the NOAA Fisheries Seafood Inspection Program, the Washington State Department of Health, and the Southeast Alaska Regional Dive Fisheries Association.

SRM 2983: Inorganics in Geoduck Clam Tissue (Panopea generosa) is available for purchase at the NIST Store.