Most of us have heard references to the dangers of large, predatory fish such as swordfish, shark and tuna and correlating high levels of mercury, but is this all that a health-conscious domestic goddess has to worry about when making the weekly shopping list?
In fact, there are numerous factors to consider when questioning the health and safety issues surrounding a particular marine species:
- Where is the animal found?
- What is its life span?
- What does it primarily feed on, and how does it process its food?
- Do its tissues contain a high percentage of oil or fat?
Many of the finfish and shellfish that are typically consumed have not been tested for contaminants of any kind. Short of turning your kitchen into a chemistry lab and testing your grub yourself, here are a few of the main areas of concern and how to best minimize the risk of over-exposure:
Heavy metals such a mercury and lead are currently hot topics when it comes to seafood. When contaminants are released into the air from industrial sources, they eventually find their way down into our water supplies through condensation and rain. Mercury is then transformed into a substance called ‘methylmercury’ in our oceans. As most animals (including humans!) have difficulty ridding themselves of heavy metals, these substances have a tendency to bioaccumulate, meaning that the body tissues of many marine organisms will contain metals in concentrations which are reflective of the contaminated sources which they have consumed over their lifetimes. For this reason, large, long-lived species which eat other long-lived species are most likely to have stored metals in their bodies.
Examples of species at risk include shark, swordfish, tilefish, king mackerel, and albacore tuna. Avoiding these fish completely would be the best way to lower your risk of metal poisoning, especially for pregnant women and young children.
Agricultural pesticides frequently seep into water supplies including lakes, rivers, creeks and oceans due to terrestrial runoff from storm water or irrigation. Animals at risk include any commercially or recreationally caught fish which live and feed in coastal and fresh waters. Knowing the source of your seafood will be helpful in avoiding pesticide-contaminated seafood. Ideally, one should only purchase seafood from a reputable fish monger who can (and will) answer any questions you might have about where the food for sale is coming from. Checking for local advisories is also essential if you plan to participate in recreational fishing activities.
As the pharmaceutical industry for both humans and aquaculture continues to grow, medication concentrations in our seafood supply will also continue to increase. Pharmacological substances primarily find their way into rivers and streams through treated sewage water (most sewage treatment centers are not equipped to remove these chemical substances). In addition, diseases which plague fish farms are often combated with antibiotics or anti-parasitic medication, which can remain in seafood tissue long after they were administered. There is not much that a consumer can do to avoid pharmaceuticals in the wild population, but buying farmed fish which has been tested and deemed safe to eat would be the best option if you do not choose wild stock animals when shopping.
PCBs, or ‘polychlorinated biphenyls,’ are industrial compounds with uses including formulating lubricants, hydraulic fluids, and some plastic products. The use of these substances has been banned in the U.S., but they continue to be employed elsewhere in the world. Research has shown PCBs to be carcinogenic (cancer-causing). PCBs accumulate in the fatty tissue of finfish (as opposed to metals, which can be found throughout the tissues, including muscles, organs, etc.), so a good way to reduce your family’s intake would be to remove as much of the fat or oil from your fish before cooking as possible. Steaming or grilling the fish in a way that oils can drip down and be collected and discarded is one way to separate the flesh from some of the fat it contains. Some of the worst offenders for PCBs are bluefish, Atlantic salmon and wild striped bass.
Dioxins are a group of chemicals which are normally formed as by-products of industrial activity, including waste-burning incinerators, production of PVC-plastics and the chlorine-bleaching of paper, and are highly toxic to marine life and humans, linked to cancer and both developmental and reproductive problems. Generally, higher levels of dioxins are found in beef and dairy than in seafood, but avoiding fish oil supplements unless they are tested and guaranteed to be free from heavy metals and have been distilled to remove chemical contaminants would be ideal.
To add a few words about shellfish, these animals generally feed off of the seabed and are scavengers. Many edible species live in shallow, inter- or intra- coastal waters, where runoff and sewage are real concerns. I personally try to avoid shellfish in general if I am unaware of the source, only choosing it as a very occasional ‘treat’. As always, research your food, arm yourself with knowledge, and then make your choices based on informed decisions, according to what you and your family feel comfortable with and what makes sense with your lifestyle, your budget and the availability of seafood in your area.
- Environmental Defense Fund’s Seafood Selector
- KidSafe Seafood Program
- Healthy Child Safe Fish Chart
- EPA Fish Advisories (U.S.A.)
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