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Mercury Levels in Commercial Fish and Shellfish

What is mercury?

Mercury is a heavy metal element that occurs naturally in the environment. Mercury is also created and released into the air through industrial pollution. From the air, mercury can enter the water in streams and oceans and be converted to methylmercury. As fish feed in the contaminated waters, the levels of methylmercury build up in their muscles. As a general rule, the bigger or older the fish, the more mercury will have build up in them. also, certain types of fish seem to accumulate mercury to a greater extent than other types.

Why is mercury a problem?

Methylmercury is the form of mercury that can potentially be harmful to women attemptimg pregnancy, unborn babies and small children. If a person regularly eats types of fish that are high in methylmercury, it can accumulate in their blood over time. Babies and small children are more sensitive to the effects of mercury and are therefore at potentially greater risk. since it takes the body many years to get rid of mercury, women may have high levels even before she attempts pregnancy.

Mercury Levels in Seafood and Fertility

As stated abobe, mercury contamination has been found in many different types of seafood. Most women are now aware of the relationship between eating contaminated seafood while pregnant and the risk of giving birth to babies with birth defects and neurologic impairment. Recent studies have also demonstrated however that mercury consumption may also be related to infertility and miscarriage.

One study found that a group of infertile men and women had higher blood levels of mercury that a similar group of men and women with normal fertility. Men who had an abnormal semen analysis and women with otherwise unexplained infertility also had higher levels. The higher levels corresponded to increased consumption of seafood.

We therefore advise all patients who are attempting to conceive to try to reduce their consumption of mercury contaminated seafood. The table below from the U.S. Department of Health and Human Services lists the levels of mercury found in many different types of seafood. You can use this as a guide but keep in mind that these numbers are subject to change.

What about fish sticks and fast food fish sandwiches?

According to the FDA/ EPA fish sticks and fast food fish sandiches are commonly made from fish that are low in mercury.

Safety tips

 

  • 1. Do not eat any of the fish that contain high levels of mercury in the list below
  • 2. Eat up to 12 ounces ( 2 average meals) a week of a variety of fish and shellfish that are low in mercury. “ND” means “not detectable”. These fish have no detectable mercury contamination and are the safest. Otherwise, the lower the number in the mercury concentration column, the lower the levels and thus the safer the fish. For example, Tilapia has lower levels than fresh water trout.
  • 3. check local advisories about the safety of fish caught by family and friends in your local lakes, rivers and coastal areas.

 

 

FDA Advisory on Mercury in Seafood

Mercury in Fish: FDA Monitoring Program

Table 1. Fish and Shellfish With Highest Levels of Mercury
SPECIES MERCURY CONCENTRATION (PPM) NO. OF
SAMPLES		 SOURCE OF DATA
MEAN MEDIAN STDEV MIN MAX
MACKEREL KING 0.730 N/A N/A 0.230 1.670 213 GULF OF MEXICO REPORT 2000
SHARK 0.988 0.830 0.631 ND 4.540 351 FDA 1990-02
SWORDFISH 0.976 0.860 0.510 ND 3.220 618 FDA 1990-04
TILEFISH (Gulf of Mexico) 1.450 N/A N/A 0.650 3.730 60 NMFS REPORT 1978
Table 2. Fish and Shellfish With Lower Levels of Mercury †
SPECIES MERCURY CONCENTRATION (PPM) NO. OF
SAMPLES		 SOURCE OF DATA
MEAN MEDIAN STDEV MIN MAX
ANCHOVIES 0.043 N/A N/A ND 0.340 40 NMFS REPORT 1978
BUTTERFISH 0.058 N/A N/A ND 0.360 89 NMFS REPORT 1978
CATFISH 0.049 ND 0.084 ND 0.314 23 FDA 1990-04
CLAM * ND ND ND ND ND 6 FDA 1990-02
COD 0.095 0.087 0.080 ND 0.420 39 FDA 1990-04
CRAB 1 0.060 0.030 0.112 ND 0.610 63 FDA 1990-04
CRAWFISH 0.033 0.035 0.012 ND 0.051 44 FDA 2002-04
CROAKER ATLANTIC (Atlantic) 0.072 0.073 0.036 0.013 0.148 35 FDA 1990-03
FLATFISH 2* 0.045 0.035 0.049 ND 0.180 23 FDA 1990-04
HADDOCK (Atlantic) 0.031 0.041 0.021 ND 0.041 4 FDA 1990-02
HAKE 0.014 ND 0.021 ND 0.048 9 FDA 1990-02
HERRING 0.044 N/A N/A ND 0.135 38 NMFS REPORT 1978
JACKSMELT 0.108 0.060 0.115 0.040 0.500 16 FDA 1990-02
LOBSTER (Spiny) 0.09 0.14 ‡ ND 0.27 9 FDA SURVEY 1990-02
MACKEREL ATLANTIC (N.Atlantic) 0.050 N/A N/A 0.020 0.160 80 NMFS REPORT 1978
MACKEREL CHUB (Pacific) 0.088 N/A N/A 0.030 0.190 30 NMFS REPORT 1978
MULLET 0.046 N/A N/A ND 0.130 191 NMFS REPORT 1978
OYSTER 0.013 ND 0.042 ND 0.250 38 FDA 1990-04
PERCH OCEAN * ND ND ND ND 0.030 6 FDA 1990-02
POLLOCK 0.041 ND 0.106 ND 0.780 62 FDA 1990-04
SALMON (CANNED) * ND ND ND ND ND 23 FDA 1990-02
SALMON (FRESH/FROZEN) * 0.014 ND 0.041 ND 0.190 34 FDA 1990-02
SARDINE 0.016 0.013 0.007 0.004 0.035 29 FDA 2002-04
SCALLOP 0.050 N/A N/A ND 0.220 66 NMFS REPORT 1978
SHAD AMERICAN 0.065 N/A N/A ND 0.220 59 NMFS REPORT 1978
SHRIMP * ND ND ND ND 0.050 24 FDA 1990-02
SQUID 0.070 N/A N/A ND 0.400 200 NMFS REPORT 1978
TILAPIA * 0.010 ND 0.023 ND 0.070 9 FDA 1990-02
TROUT (FRESHWATER) 0.072 0.025 0.143 ND 0.678 34 FDA 2002-04
TUNA (CANNED, LIGHT) 0.118 0.075 0.119 ND 0.852 347 FDA 2002-04
WHITEFISH 0.069 0.054 0.067 ND 0.310 28 FDA 2002-04
WHITING ND ND ‡ ND ND 2 FDA SURVEY 1990-02
Table 3. Mercury Levels of Other Fish and Shellfish†
SPECIES MERCURY CONCENTRATION (PPM) NO. OF
SAMPLES		 SOURCE OF DATA
MEAN MEDIAN STDEV MIN MAX
BASS (SALTWATER, BLACK, STRIPED)3 0.219 0.130 0.227 ND 0.960 47 FDA 1990-04
BASS CHILEAN 0.386 0.303 0.364 0.085 2.180 40 FDA 1990-04
BLUEFISH 0.337 0.303 0.127 0.139 0.634 52 FDA 2002-04
BUFFALOFISH 0.19 0.14 ‡ 0.05 0.43 4 FDA SURVEY 1990-02
CARP 0.14 0.14 ‡ 0.01 0.27 2 FDA SURVEY 1990-02
CROAKER WHITE (Pacific) 0.287 0.280 0.069 0.180 0.410 15 FDA 1990-03
GROUPER (ALL SPECIES) 0.465 0.410 0.293 0.053 1.205 43 FDA 2002-04
HALIBUT 0.252 0.200 0.233 ND 1.520 46 FDA 1990-04
LOBSTER (NORTHERN/AMERICAN) 0.310 N/A N/A 0.050 1.310 88 NMFS REPORT 1978
LOBSTER (Species Unknown) 0.169 0.182 0.089 ND 0.309 16 FDA 1991-2004
MACKEREL SPANISH (Gulf of Mexico) 0.454 N/A N/A 0.070 1.560 66 NMFS REPORT 1978
MACKEREL SPANISH (S. Atlantic) 0.182 N/A N/A 0.050 0.730 43 NMFS REPORT 1978
MARLIN * 0.485 0.390 0.237 0.100 0.920 16 FDA 1990-02
MONKFISH 0.180 N/A N/A 0.020 1.020 81 NMFS REPORT 1978
ORANGE ROUGHY 0.554 0.563 0.148 0.296 0.855 49 FDA 1990-04
PERCH (Freshwater) 0.14 0.15 ‡ ND 0.31 5 FDA SURVEY 1990-02
SABLEFISH 0.220 N/A N/A ND 0.700 102 NMFS REPORT 1978
SCORPIONFISH 0.286 N/A N/A 0.020 1.345 78 NMFS REPORT 1978
SHEEPSHEAD 0.128 N/A N/A 0.020 0.625 59 NMFS REPORT 1978
SKATE 0.137 N/A N/A 0.040 0.360 56 NMFS REPORT 1978
SNAPPER 0.189 0.114 0.274 ND 1.366 43 FDA 2002-04
TILEFISH (Atlantic) 0.144 0.099 0.122 0.042 0.533 32 FDA 2002-04
TUNA (CANNED, ALBACORE) 0.353 0.339 0.126 ND 0.853 399 FDA 2002-04
TUNA(FRESH/FROZEN, ALL) 0.383 0.322 0.269 ND 1.300 228 FDA 2002-04
TUNA (FRESH/FROZEN, ALBACORE) 0.357 0.355 0.152 ND 0.820 26 FDA 2002-04
TUNA (FRESH/FROZEN, BIGEYE) 0.639 0.560 0.184 0.410 1.040 13 FDA 2002-04
TUNA (FRESH/FROZEN, SKIPJACK) 0.205 N/A 0.078 0.205 0.260 2 FDA 1993
TUNA (FRESH/FROZEN, YELLOWFIN) 0.325 0.270 0.220 ND 1.079 87 FDA 2002-04
TUNA (FRESH/FROZEN, Species Unknown) 0.414 0.339 0.316 ND 1.300 100 FDA 1991-2004
WEAKFISH (SEA TROUT) 0.256 0.168 0.226 ND 0.744 39 FDA 2002-04