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For Immediate Release
June 28, 2023

Board of Water Supply Confirms Low Level Detection of PFAS at Pearl City Shaft

HONOLULU - The Board of Water Supply (BWS) has confirmed the low-level detection of Perfluorohexanesulfonic acid (PFHxS) at the BWS Pearl City Shaft, at the levels shown in the table below.  The BWS reported the findings to the Hawaii Department of Health (DOH) in accordance with Hawaii State Law.

On March 14, 2023, the U.S. Environmental Protection Agency (EPA) proposed a Hazard Index (HI) to determine the combined risk of four specific PFAS chemicals in drinking water at a site and Perfluorohexanesulfonic acid (PFHxS) is one of them.  The Hazard Index is calculated by summing the ratios of each detected compound amount in ppt, relative to its Health-Based Water Concentration. The table below shows the amounts of Perfluorohexanesulfonic acid (PFHxS) detected relative to EPA’s proposed Hazard Index and to existing DOH environmental action levels (EALs).

The Hazard Index of 0.29 is below EPA’s 1.0 compliance threshold.  The Perfluorohexanesulfonic acid (PFHxS) amount of ND - 2.6 ppt is also less than the DOH environmental action level (DOH EAL) of 19 ppt.  Based on these conditions, a significant health risk is not expected.  DOH has advised however, that those with concerns may still use a home filtration option to reduce PFAS. 

BWS detected Perfluorohexanesulfonic acid (PFHxS) as part of its PFAS testing program.  Multiple samples were tested to confirm the finding and improvements in test methods and technology enable its detection at these very low levels.  Pearl City Shaft is located in Pearl City and serves an area from Lehua Community Park to Pearl City District Park. 

Perfluorohexanesulfonic acid (PFHxS) is in the PFAS group of fluorinated organic chemicals which have been used extensively in consumer products such as carpets, clothing, fabrics for furniture, paper packaging for food, and other materials (e.g., cookware) designed to be waterproof, stain-resistant, or non-stick.  They also have been used in fire-retarding foam.

Manager and Chief Engineer Ernest Lau stated, “We take our kuleana to provide safe drinking water to our community seriously and will continue to test for PFAS chemicals and monitor for any changes.”



Kathleen Pahinui 
Information Officer 
Honolulu Board of Water Supply
Phone: (808) 748-5319