DOH: Trace amount of toluene detected in Upper Kula water system

Toluene has been detected for the first time in water samples collected at Upper Kula Treatment Plant, which is part of Maui Department of Water Supply’s (MDWS) Upper Kula water system (Public Water System HI0000215) and serves part of the Upcountry area on the island of Maui.

Toluene detections were confirmed in lab reports, dated Aug. 14, 2023, and Aug. 16, 2023.  MDWS notified the Department of Health of the results on Aug. 28, 2023. The Method Reporting Limit (MRL) is the lowest amount (minimum concentration) of a chemical detected in a sample that can be considered reliable. The MRL for toluene is 0.5 parts per billion (ppb). 

The detected level for toluene at the Upper Kula Treatment Plant was less than the MRL and well below the federal and state Maximum Contaminant Level (MCL) of 1,000 ppb. The federal and state standards are set to avoid health risks based on a lifetime of consuming water containing that level of contaminant.

Toluene is predominantly used as an industrial feedstock and a solvent. It is the main component of paint thinner, permanent markers, contact cement and certain types of glue. It may be discharged from petroleum factories.

The presence of toluene was detected after the Upper Kula Wildfire in August of 2023. This strongly suggests its presence was an artifact of the wildfire impacting the surface water source for the Upper Kula Treatment Plant, according to the DOH. Further monitoring is planned by MDWS at the Upper Kula Treatment Plant.

To date, the Upper Kula water system is, and continues to be, in compliance with federal and state toluene standards for drinking water, according to the state Department of Health.

An unsafe water advisory remains in effect for parts of Kula and Lahaina following the recent wildfires.

• Water and Wastewater Updates: Regular updates on the status of water and wastewater services in impacted areas.
• Maps and Data: Interactive maps and data resources to facilitate navigation of impacted areas during the recovery process.

This toluene information was issued in accordance with Hawaiʻi Revised Statutes Section 340E‑24, which requires the drinking water system to notify DOH of any previously undetected contaminant within seven days of detecting the contaminant. DOH then has 14 days to notify the public through the media.