Saitama Water Pollution Hits 4-Year Low as PFAS Found in Groundwater

Saitama Prefecture announced on July 21 that water quality standards achievement fell to 86% in fiscal 2025, the lowest level in four years. The prefecture detected organic fluorine compounds (PFAS) at one location in the Oiroi River in Kawagoe City, and found cadmium, lead, arsenic, and other heavy metals exceeding environmental standards at four groundwater points. Governor Ono attributed the decline partly to rainfall 80% below the previous year, which reduced the natural dilution of pollutants.

Water quality standards miss targets across 38 rivers

Of 44 rivers tested, 38 met biological oxygen demand (BOD) standards, down from the previous year. The prefecture’s five-year plan aimed for 100% BOD achievement by fiscal 2026. Saitama tested 94 locations across 44 rivers and 3 lakes as part of its water quality monitoring program under the Water Pollution Prevention Law.

PFAS and heavy metals found in groundwater and surface water

One location in the Oiroi River exceeded guideline values for PFAS (PFOS and PFOA). In separate groundwater surveys across 682 districts, four points showed environmental standard exceedances: cadmium and lead in Kumagaya City, lead in Hanno City, and arsenic and fluorine in Kumagaya City. Nitrate nitrogen and nitrous acid nitrogen also exceeded limits in three locations including Ageo City and Fujimino City.

Household wastewater drives 70% of pollution burden

The prefecture identified household wastewater as the primary pollution source, accounting for approximately 70% of water quality degradation. The EPA invested over USD 1 billion in state drinking water programs in 2026 to address PFAS contamination globally. Saitama plans to accelerate conversion to combined treatment septic tanks and enforce stricter wastewater standards for factories and businesses.

Low rainfall reduced natural pollution dilution

Fiscal 2025 rainfall was approximately 80% below the previous year, limiting the natural dilution effect that typically helps reduce pollutant concentrations. Governor Ono stated that this weather pattern significantly contributed to the decline in water quality metrics. The prefecture will intensify efforts on household wastewater reduction to meet its 26-year-degree BOD target of 100% achievement.

Final Thoughts

Saitama’s water quality decline reflects both environmental factors and persistent household wastewater pollution. The prefecture must accelerate septic tank upgrades and industrial compliance to recover achievement rates and meet its 2026 targets.

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