TOKYO, Feb. 18 (Xinhua) -- Authorities in Japan's Ishikawa Prefecture and Japanese chemical company DIC said that potentially harmful PFAS chemicals detected in groundwater at one of the company's factories far exceeded the national safety standard.

According to the officials, groundwater at a DIC factory in Hakusan City, Ishikawa Prefecture, contained PFAS, or perfluoroalkyl and polyfluoroalkyl substances, at levels nearly 2,000 times higher than Japan's national limit.

Kyodo News reported on Tuesday that tests found a maximum concentration of 99,600 nanograms per liter of combined PFOS and PFOA, two of the most common types of PFAS, at one location, about 1,992 times Japan's standard.

DIC said the factory had produced PFOS prior to 2003. Following the findings, local authorities have advised residents living within a roughly 500-meter radius of the affected well not to drink the well water.

PFAS refers to a large group of organic fluorine compounds, which are widely used in industrial products. These chemicals are highly persistent and difficult to break down, and some have been shown to accumulate in the environment and the human body, potentially causing health problems. ■