News Navigator: What chemicals have been detected around US bases in Japan?

The Mainichi Shimbun answers some common questions readers may have about organic fluorine compounds that have been detected near U.S. military bases and other locations in Japan.

Question: What kind of chemicals have been detected?

Answer: There has been a series of discoveries of organic fluorine compounds exceeding government regulations in rivers, groundwater and spring water near U.S. bases in Okinawa, Kanagawa, and other prefectures. These chemicals are called perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA).

Q: What were those chemicals used for?

A: They have been used in fire extinguishing agents, water-repellent fabrics and food wrappers because of their properties such as water and oil repellency and heat resistance. They were also used to manufacture non-stick frying pans.

Q: Are there any health concerns?

A: Regarding the effects of PFOA on the human body, the International Agency for Research on Cancer states that it may be carcinogenic. In addition, there are reports suggesting that such chemicals are associated with elevated cholesterol levels and low birth weight, as well as the reduced effectiveness of vaccinations in infants.

Q: What if we just stopped using these chemicals?

A: Since they are mostly not degradable in nature, they are also referred to as "eternal chemicals." They are prone to remain inside the human body and have even been detected in blood. Experts point out that "this is a problem that will not end even if their production is banned."

Q: Are these chemicals regulated?

A: The Stockholm Convention on Persistent Organic Pollutants, which regulates toxic chemicals internationally, has in principle banned the production, use, import and export of PFOA since 2019. The use of PFOS was also banned with some exceptions. Within the guidelines for drinking water safety, the U.S. Environmental Protection Agency last June lowered the standard values for these chemicals. In Japan, they have been found near U.S. bases and other areas, but the sources and areas of contamination are not fully known. The Japanese government is considering reviewing the target values for these substances in water.

--- Target values for tap water in Japan and guidelines for drinking water in the U.S., and World Health Organization (WHO) proposal

Japan: 50 nanograms (1 nanogram is one-billionth of a gram) per liter for combined PFOS and PFOA

U.S.: 0.02 nanograms per liter for PFOS / 0.004 nanograms per liter for PFOA (before last June, 70 nanograms per liter for combined PFOS and PFOA)

WHO proposal: 100 nanograms per liter each for PFOS and PFOA

(Japanese original by Mikako Shimogiri, Lifestyle and Medical News Department)