Heavy metals in food databaseVegetables, tubers and teaChecked 2026.10.03
Taro and potatoes: cadmium, lead
For lead in taro, some unpeeled samples were at or above the limit of quantification (40 of 59 samples in fiscal 2015), whereas in a MAFF survey (fiscal 2015) all 59 peeled samples were below the limit of quantification (0.01 mg/kg). For cadmium, taro averaged 0.04 and peaked at 0.42, and potatoes averaged 0.02 and peaked at 0.08 mg/kg.
Levels measured in Japanese government surveys and studies
| Metal | Form / state | Mean | Range / max | Samples | Survey |
|---|---|---|---|---|---|
| Cadmium | Total cadmium, taro (edible part) | 0.04 (median 0.03) | max 0.42 | 600 samples | MAFF, fiscal 2009–10 |
| Cadmium | Total cadmium, potato (jagaimo) | 0.02 (median 0.02) | max 0.08 | 240 samples | MAFF, fiscal 2009–10 |
| Lead | Total lead, taro (unpeeled) | 0.01–0.02 | max 0.09 | 59 samples (19 below the limit of quantification) | MAFF, fiscal 2015 |
| Lead | Total lead, taro (unpeeled) | 0.01–0.02 | max 0.36 | 300 samples (246 below the limit of quantification) | MAFF, fiscal 2008 |
| Lead | Total lead, taro (peeled) | 0.00–0.01 | all samples below the limit of quantification (0.01) | 59 samples | MAFF, fiscal 2015 |
| Lead | Total lead, potato | 0.00–0.04 | max 0.04 | 100 samples (99 below the limit of quantification) | MAFF, fiscal 2003–05 |
| Arsenic | Total arsenic, taro (unpeeled) | 0.01 | max 0.04 | 98 samples | MAFF, fiscal 2003–05 |
| Arsenic | Total arsenic, taro (peeled) | 0.006 | — | 29 samples | MAFF, fiscal 2003–05 |
Units are mg/kg (= ppm), fresh. A range such as “0.00–0.01” runs from the mean with samples below the limit of quantification counted as 0 to the mean with them counted at the limit of quantification. The unpeeled and peeled results differ in the number of samples and the years, so they are not a comparison on the same samples.
Limits (Japan, international, EU)
| Set by | Limit | Note |
|---|---|---|
| Japan (Food Sanitation Act) | No standard for cadmium, lead, or arsenic | The cadmium standard covers only rice and mineral waters |
| Codex (international standards) | Cadmium, potatoes 0.1 (peeled) / lead, root and tuber vegetables 0.1 | — |
| EU (Regulation 2023/915) | Cadmium, root vegetables and tubers 0.10 (potatoes peeled) / lead, root and tuber vegetables 0.10 | — |
Good to know
- For lead in unpeeled taro, maximums of 0.36 (fiscal 2008) and 0.09 (fiscal 2015) were found, whereas all 30 peeled samples in fiscal 2003 and all 59 in fiscal 2015 were below the limit of quantification. The material gives no explanation for the reason, and it is not known whether the skin or the soil clinging to it is the cause.
- Cadmium in taro averages 0.04, with a 95th percentile of 0.14 and a maximum of 0.42 mg/kg, which is on the higher side among vegetables and tubers. Potatoes averaged 0.02 with a maximum of 0.08. Japan has no standard for either, and the Codex and EU limit for root vegetables and tubers (0.1) is a reference using another country’s yardstick.
- Total arsenic in taro is an order of magnitude lower than in rice or seaweed, averaging 0.01 unpeeled and 0.006 mg/kg peeled.
- In the total diet study (2024), cadmium in the group of millets and tubers was 2.09 μg/day (about 16% of the overall 13.4) and lead was 0.27 μg/day (about 7% of the overall 3.96). MAFF explains that “even if concentrations are lower than in other foods, the contribution to intake is large when a lot is eaten.”
- No Japanese public test values were found for the proportion that falls with cooking such as washing or boiling.
Reducing it at home (shown in tests)
- Peeling taro: for lead, 40 of 59 unpeeled samples (fiscal 2015) were at or above the limit of quantification, whereas all 59 peeled samples tested (fiscal 2015) were below the limit of quantification (0.01 mg/kg). Total arsenic goes from an average of 0.01 (98 samples) to 0.006 (29 samples) (MAFF. The unpeeled and peeled results are different sets of samples)
Related explainers
Pages for each metal
Sources
- MAFF, “Survey of lead contained in agricultural products”
- MAFF, “Lead intake from food and comparison with other countries”
- MAFF, “Survey of cadmium in domestic agricultural products (fiscal 2009–14)”
- MAFF, cadmium survey data (attachment, agricultural products, Table 3.3)
- MAFF, “Survey of arsenic contained in food”
- MHLW research grant, Total Diet Study, fiscal 2024, sub-study report
- EU Regulation 2023/915 (maximum levels for contaminants 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.