Heavy metals in food databaseFishChecked 2026.10.03
Mackerel: mercury, arsenic
Mackerel (masaba, chub mackerel) is a fish on the low side for mercury, with an average total mercury of 0.151 ppm (212 samples) in the national compilation. The MHLW lists saba as an example of fish that “need no caution.” For arsenic, mackerel bought in Fukuoka City had total arsenic of 1.5–2.7 ppm, 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 | Chub mackerel (masaba), total mercury | 0.151 | max 0.600 | 212 samples | MHLW, compiled through fiscal 2008 |
| Mercury | Chub mackerel (masaba), methylmercury | 0.232 | 0.100–0.320 | 13 samples | MHLW, compiled through fiscal 2008 |
| Mercury | Spotted mackerel (goma-saba), total mercury | 0.153 | max 0.540 | 96 samples | MHLW, compiled through fiscal 2008 |
| Mercury | Spotted mackerel (goma-saba), methylmercury | 0.102 | max 0.240 | 9 samples | MHLW, compiled through fiscal 2008 |
| Arsenic | Mackerel, total arsenic (edible portion) | (no mean given) | 1.5–2.7 | 5 samples | Journal of the Food Hygiene Society of Japan 2020 (bought in Fukuoka City) |
| Arsenic | Chub mackerel, total arsenic (muscle, dry weight) | 5.4 | — | unknown | Shinagawa et al. 1983 (FSCJ document) |
| Arsenic | Chub mackerel, inorganic arsenic (muscle, dry weight) | 0.00 (not detected) | — | 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 mackerel 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 (muscle of mackerel, genus Scomber) | The value from Regulation 2022/617, carried over into Regulation (EU) 2023/915. Wet weight. |
| 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): mackerel (Pacific chub) 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). King mackerel, which the US lists as a fish to avoid, is a different fish. |
Good to know
- Even where total arsenic is high, inorganic arsenic is small. The FSCJ summarizes the proportion of inorganic arsenic to total arsenic as 0–4% in marbled flounder (magarei), yellowtail (buri), Japanese horse mackerel (maaji), chub mackerel, Pacific saury (sanma), and Japanese sardine (maiwashi). In the 1983 report, chub mackerel muscle had total arsenic of 5.4 and inorganic arsenic of 0.00 (dry weight).
- The 5 mackerel bought in Fukuoka City had total arsenic of 1.5–2.7 ppm, and arsenobetaine (the organic arsenic common in fish) was 26–33% of total arsenic, as As. About 60% of Japanese people’s total arsenic intake comes from fish and shellfish, but only about 2% of their inorganic arsenic intake (MAFF). → Arsenic page
- 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 also says that knowledge of the toxicity of organic arsenic is limited and more data are needed.
- Mercury is on the low side, and in the MHLW’s sample menus, mackerel is among the foods that need no caution. Methylmercury in chub mackerel (0.232 ppm, 13 samples) is higher than total mercury (0.151 ppm, 212 samples) because different samples were measured. One serving (about 80 g) is about 17% of the tolerable weekly intake at the average methylmercury, and about 11% at the average total mercury (Urayomi’s calculation).
- Set beside US advice (Best Choices) and the EU maximum level (0.30 ppm), the averages in the Japanese compilation were lower. However, the yardsticks for standards differ by country. → How Japan’s standards differ from other countries’
- Cadmium is low in muscle: chub mackerel was <0.01 (maximum 0.01, 18 samples) in the MAFF survey. In a questionnaire across 14 regions of Japan, 50.7% of people said they eat mackerel “often.”
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.