The Oregon Health Authority is updating an existing health advisory to include gaper clams (Tresus capax), which were found to contain high levels of naturally occurring arsenic.
The advisory was updated today by the OHA Public Health Division after gaper clams were tested during a second round of sampling. It now applies to soft-shell clams (Mya arenaria) and gaper clams collected anywhere along the Oregon Coast. OHA recommends removing the skin from the siphon, or “neck” of soft-shell and gaper clams before eating them. This is because the inorganic arsenic that is harmful to human health is concentrated in the siphon skin. Removal of the skin before eating reduces the inorganic arsenic to levels that are not harmful.
The advisory is most important for recreational harvesters who dig their own clams. Soft-shell and gaper clams are collected primarily from estuaries and intertidal regions of the Oregon Coast.
Limited commercial harvest and sale of gaper clams for human consumption occurs in Oregon. The Oregon Department of Agriculture (ODA) regulates the safety of commercially harvested shellfish. ODA will ensure that commercial dealers instruct retailers and consumers to remove siphon skins from gaper clams before eating them.
Those planning to eat soft-shell or gaper clams with or without siphon skins should review OHA’s recommended meal limits, available at www.healthoregon.org/fishadv.
Two other clam species, cockles and butter clams, also were tested for arsenic during the same sampling period. Arsenic levels in both of these species were found to be well below the level that is harmful to human health, so cockles and butter clams are not included in the health advisory update. As mentioned in the July 13 advisory for soft-shell clams, California mussels and purple varnish clams also can be harvested and consumed without concern.
Public health officials say that since the arsenic detected in clams is naturally occurring, the advisory is likely to be permanent.
In addition to arsenic, testing included a wide variety of other potential contaminants to shellfish, including metals, pesticides, polychlorinated biphenyls, dioxins, tributyltin, flame retardants and other substances. None of these other contaminants were present in any of the species at high enough concentrations to pose a risk to human health.
By issuing the advisory, health officials hope to increase the public’s awareness of shellfish contaminants and ways to reduce human exposure to them. While it is important for people to know about contaminants in shellfish, it is equally important to include shellfish as part of a healthy diet.