Heavy metals in food databaseOtherChecked 2026.10.03
Tap water and mineral water: lead, arsenic
The tap water quality standards are 0.01 mg/L or less for lead, 0.01 for arsenic, and 0.003 for cadmium. 1.92 million lead service pipes remain in Japan’s water supply systems nationwide (fiscal 2023). Until they are replaced, the FSCJ advises using the first water of the morning and water after a long absence for purposes other than drinking.
Levels measured in Japanese government surveys and studies
| Metal | Form / state | Mean | Range / max | Samples | Survey |
|---|---|---|---|---|---|
| Lead | Total lead, drinking water group (total diet study samples. Bayesian posterior mean 0.315 ng/g) | 0.0003 | — | Samples from 10 regions | MHLW research grant, Total Diet Study, fiscal 2024 |
Water is written in mg/L (treating 1 L of water as 1 kg, the number is the same as mg/kg). The lead in the table is a value estimated from the total diet study’s “drinking water” group and is not a measured value for the tap water of any individual home. No Japanese public measured values for mineral water were found.
How much to eat (official advice)
- FSCJ (2021): in homes where lead service pipes remain, until they are replaced, use the first water of the morning and water after a long absence for purposes other than drinking (a guide is 10–15 L). It also advises checking whether any lead service pipes remain
Limits (Japan, international, EU)
| Set by | Limit | Note |
|---|---|---|
| Japan (Waterworks Act and MHLW ordinance on water quality standards) | Lead 0.01 mg/L, arsenic 0.01 mg/L, cadmium 0.003 mg/L, mercury 0.0005 mg/L or less | MHLW Ordinance No. 101 of 2003 (Heisei 15) |
| Japan (Food Sanitation Act, standards for soft drinks) | Soft drinks other than mineral waters: arsenic and lead must not be detected (tin 150.0 ppm or less for those in metal containers) / mineral waters: cadmium 0.003, lead 0.05, arsenic 0.05 mg/L or less | Component standards for soft drinks under the Food Sanitation Act. The “must not be detected” standard for cadmium was removed in 2014 for soft drinks other than mineral waters |
| Codex (international standards) | Natural mineral water: lead 0.01 mg/L, arsenic 0.01 mg/L, cadmium 0.003 mg/L | — |
| WHO (guideline values) | Lead 0.01 mg/L, arsenic 0.01 mg/L | According to MAFF’s page |
Good to know
- Lead service pipes in water supply systems fell from 5.09 million (fiscal 2005) to 3.03 million (fiscal 2014) to 1.92 million (fiscal 2023), but the decline has slowed since fiscal 2014. MLIT has set a target of eliminating 150,000 a year through the end of fiscal 2028.
- Lead in the Japanese diet as a whole was about 4 μg/day in 2024, and the drinking water group was 0.04 μg/day. However, these are national average values and are separate from the concentration in the water of an individual home (such as one where lead service pipes remain).
- For arsenic, in the water supply statistics (fiscal 2008), 4,795 of 5,289 treated water sites were at or below 1 μg/L. One site exceeded the standard (10 μg/L). In the total diet study as well, intake of total arsenic from drinking water was very small (on the order of 0.1 μg/day).
- It could not be confirmed whether drinking well water is covered by the tap water quality standards. In 2003 in Ibaraki Prefecture, well water was contaminated by the illegal dumping of waste containing diphenylarsinic acid derived from the former Japanese military, and residents suffered health effects (MAFF).
- Cooking rice in water containing arsenic increases the arsenic in the rice (an experiment cooking with water at 10 and 50 μg/L, Menon et al. 2024). Arsenic in Japanese tap water is managed to be at or below the standard. For the story of rice, see arsenic and cadmium in brown and white rice.
- No Japanese public measured values for mineral water were found. The component standards for soft drinks other than mineral waters say that lead and arsenic must not be detected. For mineral waters, the standards are lead 0.05, arsenic 0.05, and cadmium 0.003 mg/L or less.
Related explainers
Pages for each metal
Sources
- Ordinance on water quality standards (e-Gov Law Search)
- MLIT, materials of the study group on revising the guide to replacing lead service pipes
- FSCJ, “Q&A on the lead assessment report” (2021)
- MHLW research grant, Total Diet Study, fiscal 2024, sub-study report
- FSCJ, “Food health impact assessment: arsenic” (December 2013. The state of treated water)
- MAFF, “Basic information on arsenic”
- Menon M et al. Sci Total Environ 2024 (cooking with arsenic-containing water)（PMID 38176556）
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.