Korean authorities have intensified safety checks on imported Chinese cabbage and kimchi — staples of Korean cuisine — after a Chinese supplier was found to have used formaldehyde, a known human carcinogen, to extend the shelf life of harvested cabbages. Central and local authorities say they have strengthened inspections at ports of entry while expanding testing for the chemical and other potentially harmful substances in food ingredients from China. On Monday, Seoul Mayor Oh Se-hoon visited the city-run Seoul Research Institute of Public Health and Environment to observe the testing process, including sample preparation and detailed laboratory analysis of Chinese cabbage and cabbage kimchi collected for screening. “Public anxiety over Chinese food ingredients has grown significantly following the discovery of a case in which formaldehyde was used in Chinese cabbage kimchi,” Oh said. “We will use this opportunity to strengthen regular inspections — not only for formaldehyde, but also to determine whether Chinese food ingredients are exposed to heavy metals, artificial color