[News Terms] 'Ozone Advisory' Issued in Downtown Seoul

An 'Ozone Advisory' is issued when the ozone concentration in the atmosphere exceeds 0.12 ppm per hour. Ozone (O₃) is a faint blue gas produced by oxygen in the atmosphere reacting with ultraviolet (UV) rays or electrical discharge, and it has a smell similar to chlorine. The ozone layer in the atmosphere absorbs most of the ultraviolet rays emitted by the sun.

When present in appropriate amounts, ozone acts as a strong oxidizer with sterilizing and deodorizing effects. However, if the ozone concentration rises above the standard level, it irritates the respiratory system and eyes, causing coughing and stinging eyes, and in severe cases, it can lead to reduced lung function, harming the human body as well as crops.

In summer, due to longer daylight hours and stronger ultraviolet radiation, more energy is provided for the chemical reactions that promote ozone formation, resulting in the highest ozone concentrations. During the day, ozone levels peak between 2 PM and 5 PM. Especially in urban areas with heavy automobile traffic and regions that emit large amounts of volatile organic compounds (VOCs), ozone levels tend to be higher.

An ozone advisory was issued for the entire Seoul area on the afternoon of the 23rd, marking the first of the year.
[Photo by Yonhap News]

Korea introduced the ozone alert system in 1995. Each local government head issues an advisory when the ozone concentration exceeds 0.12 ppm per hour by region, a warning at 0.3 ppm or higher, and a severe warning if it rises above 0.5 ppm.

Exposure to ozone concentrations at the 'Advisory' level for more than one hour causes irritation to the respiratory system and eyes and induces coughing. Therefore, when an advisory is issued, respiratory patients, the elderly, and children under five years old should avoid going outside, and drivers should also refrain from using vehicles.

When a 'Warning' is issued, incineration facilities and automobiles are requested to limit use, and kindergartens and schools in the affected areas should refrain from outdoor activities. After a 'Severe Warning' is issued, exposure for six hours causes airway constriction, dry coughing, and chest pain. Ozone, which does not dissolve well in water, can penetrate deep into the lungs over prolonged exposure, causing inflammation and pulmonary edema, and in severe cases, respiratory distress leading to fainting.

As of 1 PM on the 16th, the Seoul Metropolitan Institute of Health and Environment issued an ozone advisory for downtown Seoul and the northeast, northwest, and southwest areas. The affected districts include 21 locations: Jongno, Jung-gu, Yongsan, Seongdong, Gwangjin, Dongdaemun, Jungnang, Seongbuk, Gangbuk, Dobong, Nowon, Mapo, Seodaemun, Eunpyeong, Yangcheon, Gangseo, Guro, Geumcheon, Yeongdeungpo, Dongjak, and Gwanak.