Heavy metals in food databaseFishChecked 2026.10.03
Sardines, horse mackerel, and Pacific saury: mercury, arsenic
Sardines, horse mackerel, and Pacific saury are fish with low mercury: in national compilations, average total mercury is 0.024–0.052 ppm. The MHLW uses saury, horse mackerel, mackerel, sardines, and squid as examples of fish that pregnant women need not worry about. For arsenic, total arsenic is on the high side, but inorganic arsenic in fish muscle is summarized as 0–4% of total arsenic.
Levels measured in Japanese government surveys and studies
| Metal | Form / state | Mean | Range / max | Samples | Survey |
|---|---|---|---|---|---|
| Mercury | Japanese sardine (maiwashi), total mercury | 0.024 | max 0.230 | 159 samples | MHLW, compiled through fiscal 2008 |
| Mercury | Japanese anchovy (katakuchi-iwashi), total mercury | 0.032 | max 0.090 | 31 samples | MHLW, compiled through fiscal 2008 |
| Mercury | Japanese anchovy (katakuchi-iwashi), methylmercury | 0.017 | max 0.050 | 3 samples | MHLW, compiled through fiscal 2008 |
| Mercury | Japanese horse mackerel (maaji), total mercury | 0.049 | max 0.470 | 378 samples | MHLW, compiled through fiscal 2008 |
| Mercury | Japanese horse mackerel (maaji), methylmercury | 0.213 | max 0.280 | 8 samples | MHLW, compiled through fiscal 2008 |
| Mercury | Pacific saury (sanma), total mercury | 0.052 | max 0.170 | 195 samples | MHLW, compiled through fiscal 2008 |
| Arsenic | Sardine, total arsenic (edible portion) | (no mean given) | 2.5–3.5 | 5 samples | Journal of the Food Hygiene Society of Japan 2020 (bought in Fukuoka City) |
| Arsenic | Horse mackerel, total arsenic (edible portion) | (no mean given) | 1.9–7.0 | 5 samples | Journal of the Food Hygiene Society of Japan 2020 (bought in Fukuoka City) |
| Arsenic | Japanese sardine, total arsenic (muscle, dry weight) | 17.3 | — | unknown | Shinagawa et al. 1983 (FSCJ document) |
| Arsenic | Japanese sardine, inorganic arsenic (muscle, dry weight) | 0.28 | — | unknown | Shinagawa et al. 1983 (FSCJ document) |
| Arsenic | Japanese horse mackerel, total arsenic (muscle, dry weight) | 25.6 | — | unknown | Shinagawa et al. 1983 (FSCJ document) |
| Arsenic | Japanese horse mackerel, inorganic arsenic (muscle, dry weight) | 0.06 | — | unknown | Shinagawa et al. 1983 (FSCJ document) |
| Arsenic | Pacific saury, total arsenic (muscle, dry weight) | 5.5 | — | unknown | Shinagawa et al. 1983 (FSCJ document) |
| Arsenic | Pacific saury, inorganic arsenic (muscle, dry weight) | 0.22 | — | unknown | Shinagawa et al. 1983 (FSCJ document) |
Units are mg/kg (= ppm). Mercury values appear to be wet weight (the sources do not say). The arsenic values include edible-portion values from fish bought in Fukuoka City (the sources do not say whether wet or dry weight) and dry-weight values from a 1983 report; they are labeled separately in the form column. Dry-weight values cannot be compared directly with wet-weight values.
Limits (Japan, international, EU)
| Set by | Limit | Note |
|---|---|---|
| Japan (mercury) | Total mercury 0.4 ppm, methylmercury 0.3 ppm (provisional regulatory limit for fish and shellfish) | A value notified by the Ministry of Health and Welfare in 1973 (Showa 48). Tuna-type fish, fish and shellfish from rivers (excluding lakes and marshes), deep-sea fish and shellfish, and others are exempt; other fish and shellfish are covered. |
| Codex (mercury) | Methylmercury 0.5 mg/kg (guideline level for fish). For predatory fish such as shark, swordfish, and tuna, 1 mg/kg | A 1991 guideline of the Codex Alimentarius Commission. |
| EU (mercury) | 0.30 mg/kg (sardines and anchovies). Horse mackerel and saury have no individual value and fall under the general 0.50 mg/kg for fish and fishery products | The value from Regulation 2022/617, carried over into Regulation (EU) 2023/915. Wet weight. Horse mackerel and saury are on neither the 1.0 list nor the 0.30 list, so they appear to fall under the general category. |
| Japan (arsenic) | No arsenic limit for fish and shellfish | The table of “current regulations” in the FSCJ’s evaluation report does not list a standard or specification for fish and shellfish. We have not checked the individual articles of the laws. |
| US FDA/EPA advice (2021) | Best Choices (2–3 times a week): sardines, anchovies, and others | Advice for people who are pregnant or breastfeeding and for children aged 1 to 11. One serving is about 113 g (4 ounces). |
Good to know
- Mercury is on the low side. The averages in the national compilation are 0.024 ppm for Japanese sardine, 0.049 for horse mackerel, and 0.052 for saury. Calculated with total mercury instead of methylmercury, the mercury in one serving (about 80 g) is about 2–4% of the weekly tolerable amount (Urayomi’s calculation). Methylmercury in horse mackerel is 0.213 ppm (8 samples), higher than total mercury (0.049, 378 samples), but that is from few samples, measured in different samples from the total mercury.
- In sardines, arsenobetaine (the organic arsenic common in fish) was low at 3–5% of total arsenic, and dimethylarsinic acid (DMA, another organic arsenic) was 16–24%, a different profile from the other fish (Fukuoka City survey, 5 samples). DMA is a different compound from inorganic arsenic, and its toxicity is evaluated separately.
- Inorganic arsenic was very small compared with total arsenic. In the 1983 report (dry weight, number of samples unknown), total arsenic was 17.3 in Japanese sardine, 25.6 in Japanese horse mackerel, and 5.5 in Pacific saury, against inorganic arsenic of 0.28, 0.06, and 0.22. The FSCJ summarizes inorganic arsenic in fish muscle as 0–4% of total arsenic.
- No official document asserts that “organic arsenic is harmless.” MAFF writes that its effects are generally said to be small but that its effects in the body are not understood, and the FSCJ says that knowledge of the toxicity of organic arsenic is limited. → Arsenic page
- Cadmium is low in muscle: in the MAFF survey, Japanese sardine was 0.01 (maximum 0.03, 15 samples) and Japanese horse mackerel <0.01 (maximum <0.01, 15 samples). In a questionnaire across 14 regions of Japan, 52.3% of people said they eat saury “often,” 42.8% horse mackerel, and 29.0% sardines.
- Of the inorganic arsenic Japanese people take in, about 2% comes from fish and shellfish (0.4 of 18.3 μg/day), and about 70% comes from rice. The fish survey values are from a compilation through fiscal 2008 and old one-off reports, and may differ from fish on the market today. → How Japan’s standards differ from other countries’
Related explainers
Pages for each metal
Sources
- MHLW, “Notes on Eating Fish and Shellfish and Mercury for Pregnant Women,” Q&A
- MHLW, Document 2-4, “Survey Results on Mercury in Fish and Shellfish (Summary)” (May 2010)
- MAFF, “Survey Data on Cadmium in Domestic Agricultural, Livestock, and Fishery Products: Fish and Shellfish” (fiscal 1997–2002)
- Towatari et al. Journal of the Food Hygiene Society of Japan 2020;61(3):86- (chemical forms of arsenic in 10 kinds of fish bought in Fukuoka City)
- FSCJ, Document 3, “Findings on Inorganic Arsenic Exposure in Japanese People” (includes the 1983 report by Shinagawa et al.)
- FSCJ, “Arsenic in Food” evaluation report (December 2013)
- MAFF, “Intake of Arsenic from Food”
- European Commission, Regulation (EU) 2022/617 (maximum levels for mercury in food)
Last checked 2026.10.03 (against the original government documents and papers, collected and cross-checked in Gemini Notebook).
Heavy metals occur naturally in soil and the sea, and every food contains small amounts. This page lists facts from government surveys, limits and assessments and from published papers; it does not judge any food as good or bad. Where there is official advice — such as on eating fish during pregnancy — follow it.