Fish and polychlorinated biphenyls (PCBs) – Mayo Clinic
mayoclinic.org · September 4, 2015
Nutrition-wise blog
Our recent blog post on eating fish during pregnancy prompted one reader to ask why we didn’t mention that salmon is high in dangerous PCBs. So what are PCBs and what risk do they pose?
Polychlorinated biphenyls (PCBs) are industrial chemicals that were manufactured from 1929 until 1979 when they were banned. PCBs have been shown to cause adverse health effects, including potential cancers, and negative effects on the immune, nervous and endocrine systems.
PCB remnants still cycle between air, water and soil, and traces are found all over the world. PCBs settle into water and sediment, where they are taken up by small organisms, fish and animals (including humans) that eat fish. PCBs accumulate in fat and in organs such as liver.
PCBs can pose serious health risks to people who frequently eat contaminated fish. PCBs can be transferred from a mother to her unborn baby, increasing the risk of preterm delivery and low birth weight. PCBs may also be transferred from mother to baby through breast milk, and exposure has been associated with learning defects.
Fish are the major dietary sources of PCBs, especially fish caught in contaminated lakes or rivers. However, small amounts are also found in meat, dairy products and drinking water.
The Food and Drug Administration (FDA) sets PCB residue limits for foods, while the Environmental Protection Agency (EPA) sets limits for lakes, streams and drinking water. In 2004 these agencies came out with guidelines for fish consumption during pregnancy but PCBs weren’t mentioned. Nor were they mentioned in last year’s draft update of the guidelines. The final guidelines are expected to be released later this year.
However, two other groups, Physicians for Social Responsibility (PSR) and the Association of Reproductive Health Professionals (ARHP), released fish consumption guidelines that do address PCBs.
The PSR/ARHP guidelines specifically mention the need for caution with fish, such as salmon, that can contain high levels of PCBs. With respect to salmon, the guidelines say:
- Canned Pacific salmon can be eaten twice a week
- Fresh or frozen wild Pacific salmon can be eaten up to twice a month
- Fresh or frozen farmed Atlantic salmon can be eaten once every 2 months
The guidelines also recommend ways to reduce PCB risks in the preparation of salmon and other fatty fish:
- Trim fatty areas (belly, top back and dark meat along the side)
- Remove or puncture skin before cooking to allow fat to drain off
- Broil, grill, roast or steam fish on a rack to allow fat to drain off
- Do not fry large fatty fish such as salmon and bluefish
Both sets of guidelines agree that:
- The benefits of eating fish outweigh the risks.
- Eating a variety of fish is a good way to minimize risks from contaminants.
- Because of high levels mercury (another common pollutant), king mackerel, shark, swordfish and tilefish should be avoided.
The bottom line: Eat a variety of fish twice a week and keep the portion size at 6 ounces (170 grams). When you eat fatty fish like salmon, make sure they’re prepared using the above guidelines. When you catch your own fish, follow local and state fish advisories for restrictions.
mayoclinic.org · September 4, 2015