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Trace levels of selenium have been found for the first time in the Maui County Department of Water Supply's Makawao water system.
Trace levels of selenium have been found for the first time in the Maui County Department of Water Supply's Makawao water system.
The department said the initial detection occurred in a sample collected during routine testing on May 29, 2026.
A follow-up test from a sample collected on June 19 confirmed selenium levels ranging from 3.7 to 4.9 micrograms per liter, the county said.
County water officials notified the state Department of Health in accordance with state requirements.
According to the U.S. Environmental Protection Agency and state Department of Health, the maximum contaminant level for selenium in drinking water is 50 micrograms per liter.
The levels detected in the Makawao water system are well below the drinking water standard, the county water department said.
"The amount of selenium detected is extremely small -- about four parts per billion, or roughly four drops in 1 billion drops of water," county water director John Stufflebean said.
"Our dedicated water professionals work every day to monitor, maintain and care for our water system, and we remain committed to providing our community with safe, reliable water."
The county said selenium is a naturally occurring mineral element found in soil, rocks and certain mineral deposits. Small amounts of selenium can enter drinking water sources through the natural erosion of mineral deposits.
According to the National Institutes of Health, selenium is a nutrient that the body needs to stay healthy, including the thyroid gland, which needs selenium to produce hormones and function properly.
The NIH said consuming very high amounts of selenium can cause severe stomach and nervous system problems, difficulty breathing and tremors, kidney or heart failure, and heart attacks.
The daily upper limit for selenium is 400 mcg for adults and 45 mcg for newborns up to six months, according to the NIH.
The county water department is required to notify state health officials whenever selenium is detected for the first time in a public water system.
The county water department said it will continue working closely with state health officials and monitoring the Makawao water system to maintain compliance with federal and state drinking water standards.
For more information, contact the County Department of Water Supply at (808) 270-7550.
More information about selenium may also be found through the National Institute of Health website: https://ods.od.nih.gov/factsheets/Selenium-Consumer/#h15