Cancer inducing toxins found in water sources near US bases in Japan: study

TOKYO -- An Environment Ministry water quality study has revealed that contamination levels at 37 water sources exceeded provisional national targets, with high levels of two types of chemical compounds suspected to induce cancer found near U.S. military bases and industrial areas throughout Japan.

This study examined the amounts of PFOS, or perfluorooctanesulfonic acid, and PFOA, or perfluorooctanoic acid, which are chemical agents that are said to cause cancer, in groundwater and other water sources in a total of 171 locations nationwide. The study found that in 37 spots in 13 prefectures including Tokyo, Osaka and Kyoto, the levels exceeded the advised standard, with a maximum of around 37 times the index figure being recorded.

The Ministry of the Environment and the Ministry of Health, Labor and Welfare had established a provisional target standard of 50 nanograms per liter as the desired amount of PFOS and PFOA contained in tap water and groundwater by May. The chemicals are categorized by the ministries as items requiring monitoring and further accumulation of knowledge regarding their impact on health.

According to the Ministry of the Environment, the study is the first to examine nationwide contamination levels for the two substances of PFOS and PFOA. As these substances are chemically stable, and repel water and oil, they have been used widely in products including foam fire extinguishers, cookware and semiconductors. Although the causes of the contamination are yet unspecified, it is thought possible that the chemical agents were emitted from military bases, factories and other places, and had accumulated in rivers and groundwater.

The ministry plans to expand the scope of examinations for this fiscal year and aims to get a better grasp on the matter. While neither the groundwater or spring water in spots that exceeded national standard figures are currently used as drinking water, the ministry will spread awareness about such concerns and is warning the owners of wells to prevent them from accidentally drinking the water.

During the previous fiscal year, the Environment Ministry examined the water quality of groundwater, rivers, spring water, lakes and marshes, and surrounding waters in the ocean near facilities that are likely to have emitted PFOS and PFOA, based on examinations conducted independently by local governments. Levels around 30 times larger than the desired standard, or 1,508 nanograms of PFOS and PFOA per liter of water, were detected in the Dakujaku River that runs through the city of Okinawa near the U.S. Kadena Air Base in southern Japan. In springs at three locations including Chunnaga in the southern Okinawa Prefecture city of Ginowan, home to U.S. Marine Corps Air Station Futenma, 168 to 1,303 nanograms of the toxic chemicals were found.

Contamination levels that surpassed advised standards were also found in groundwater in the suburban Tokyo city of Tachikawa, which is next to the U.S. military's Yokota Air Base, and a river in the city of Yamato, Kanagawa Prefecture, where the Atsugi Air Base is located.

Groundwater in the Osaka Prefecture city of Settsu also had 1,855 nanograms of the chemicals, or around 37 times the desired standard, which was the highest recorded amount for this study. There was an inclination for higher concentration levels of PFOS and PFOA in areas where chemical manufacturers and other factories are located, such as the greater Tokyo area, the Hanshin region that includes Osaka, and around the Mie Prefecture city of Yokkaichi in central Japan. A wide range of areas in the capital also exceeded standard levels of contamination.

PFOS and PFOA are known as "everlasting chemical substances" resistant to natural decomposition. They also have the characteristic of being capable of accumulating in the human body, and the International Agency for Research on Cancer has categorized PFOA as "possibly carcinogenic to humans." There are also research reports recognizing that PFOS also has repercussions on health in experiments using animals. However, there is not sufficient medical knowledge regarding the substance's potential damage on the human body.

In April, a large volume of fire extinguishing foam that contained PFOS leaked from the Futenma air station. High concentrations of the substance were detected from nearby waterways and other places, and many residents have voiced anxiety over potential damage to their health.

The chemical PFOS was designated as a restricted chemical under the Stockholm Convention, an international treaty regulating toxic chemicals, and Japan completely banned domestic manufacturing and importing of the substance in 2018. PFOA was designated as a chemical regulated by the treaty in 2019, and the Japanese government is discussing plans to completely ban the manufacturing of this substance as well.

(Japanese original by Toshiyuki Suzuki and Mayumi Nobuta, Science & Environment News Department)