Understanding Mercury in Seafood
Mercury is a naturally occurring element that is released into the environment through industrial pollution and natural processes. In aquatic ecosystems, microorganisms convert this mercury into a more toxic form called methylmercury, which is then absorbed by small marine life. The primary way humans are exposed to mercury is through eating contaminated seafood. The key to understanding mercury risk lies in a process called biomagnification.
The Science of Biomagnification
Biomagnification is the increasing concentration of a substance, such as mercury, in organisms at higher trophic levels in a food chain. Scallops, as filter-feeding shellfish, are near the bottom of the marine food chain. They consume plankton, which have absorbed low levels of methylmercury from the water. Larger, predatory fish eat many smaller fish, absorbing and accumulating all the mercury from their prey, leading to higher concentrations over time. This is why fish like shark and swordfish have much higher mercury levels than scallops.
Are Scallops High in Mercury? The Facts
Unlike larger, predatory fish, scallops have very low levels of mercury. The FDA has documented that scallops contain a mean mercury concentration of just 0.003 ppm (parts per million). This places them squarely in the "best choices" category for seafood consumption, even for vulnerable groups such as pregnant women and children.
Low Mercury Content in Scallops
There are several reasons why scallops are not a mercury concern:
- Position in the food chain: As filter feeders, scallops are at a low trophic level, meaning they do not consume other fish and therefore do not biomagnify mercury in the same way larger predators do.
- Size and lifespan: Scallops are relatively small and have a shorter lifespan compared to large, long-lived fish, which means less time to accumulate toxins.
- Rapid excretion: While some heavy metals can accumulate, especially in the digestive organs, the adductor muscle (the part most commonly eaten) in scallops shows very low concentrations.
Heavy Metals Other Than Mercury
It is important to note that while mercury is low, some studies suggest scallops may accumulate other heavy metals, particularly cadmium, depending on their environment. The health benefits of consuming scallops in moderation are generally considered to outweigh these risks for the average person.
Comparing Mercury Levels in Seafood
To put the mercury levels in scallops into perspective, consider this comparison table. Values are average parts per million (ppm) based on FDA data.
| Seafood Type | Average Mercury (ppm) | Mercury Category | Trophic Level |
|---|---|---|---|
| Scallops | 0.003 | Best Choice (Very Low) | Low |
| Shrimp | 0.009 | Best Choice (Very Low) | Low |
| Salmon | 0.022 | Best Choice (Very Low) | Low to Mid |
| Cod | 0.111 | Good Choice (Moderate) | Mid |
| Canned Tuna (light) | 0.126 | Good Choice (Moderate) | Mid |
| Halibut | 0.241 | Good Choice (Moderate) | Mid to High |
| Albacore Tuna | 0.350 | Moderate to Avoid | High |
| Swordfish | 0.995 | Avoid (High) | High |
| Shark | 0.979 | Avoid (High) | High |
How to Safely Enjoy Scallops
For the vast majority of people, incorporating scallops into a balanced diet is a safe and healthy choice. The FDA and EPA categorize scallops as a 'Best Choice' seafood, recommending 2–3 servings per week.
For those who are pregnant, nursing, or children, scallops are an excellent low-mercury option for fulfilling weekly seafood recommendations, which are important for receiving valuable nutrients like omega-3 fatty acids and Vitamin B12. For more information on mercury levels in various fish, see the FDA's advisory.
Conclusion: Scallops are a Low-Risk Seafood
Based on decades of scientific data from organizations like the FDA, the answer to "are scallops high in mercury?" is a definitive no. Their low position in the food chain and relatively short lifespan ensure they do not accumulate significant levels of this neurotoxin. This makes scallops a safe and nutritious addition to the diets of most people, including sensitive populations. While all seafood contains trace amounts of mercury, the levels in scallops are exceptionally low, allowing you to enjoy their rich flavor with minimal concern.
