Daegu Metropolitan Waterworks said 1,4-dioxane levels at the Maegok water purification plant rose to 54 micrograms per liter, exceeding the 50 micrograms recommended by the World Health Organization.

A prolonged winter drought and the ensuing loss of water in the Nakdong River, which flows into the purification center, are being blamed as the cause.

The concentration of the carcinogen has continued to rise since Monday last week, with the level soaring to 77.1 micrograms at one point yesterday morning.

“The level at the Maegok water purification plant rose due to inflow of water from the Nakdong River, whose 1,4-dioxane concentration rose to 87.9 micrograms per liter from Thursday and Friday,” said a city water official.

When measured early last week at Waegwan Bridge in Waegwan-eup, Chilgok County, North Gyeongsang Province, the concentration reached 65.3 micrograms and remained there for the following seven days.

Given 1,4-dioxane is not removed through purification, Daegu has asked residents to boil tap water. When boiled for more than 10 minutes, 90 percent of the toxic material is removed.

When the 1,4-dioxane level continues to rise and exceeds 65 micrograms per liter, the city government will restrict water consumption.

In addition Daegu will reduce daily water intake from the Nakdong River to 430,000 tons from 630,000 tons. Daily tap water production from Gachang, Unmun and Gongsan dams will be raised to 350,000 tons from 150,000 tons.

Daegu Metropolitan Waterworks provides a daily average of 780,000 tons of tap water to 880,000 households.

1,4-dioxane is a byproduct of polyester manufacturing. Polyester manufacturers at Gumi Industrial Complex in North Gyeongsang Province have in place wastewater treatment systems that destroy 1,4-dioxane.

Ulsan city authorities suspended water intake from the Nakdong River yesterday after high levels of the chemical were found. Due to a severe drought, the port city had secured 100,000 tons of water daily from the river.