HAA5 in Hawaii Drinking Water
Ranked by average HAA5 concentration (µg/L) · UCMR 4 data (2018–2020) · Data from EPA SDWIS & UCMR
HAA5 in Hawaii: what the data shows
Hawaii has 20 cities with HAA5 monitoring data from the EPA's UCMR 4 program (2018–2020). Haloacetic acids (HAA5) form when chlorine-based disinfectants react with natural organic matter in water. The state average is 3.2 µg/L — better than the 15.5 µg/L national average. No cities currently exceed the 60 µg/L EPA MCL. HAA5 is a group of five chlorinated and brominated acetic acids. Long-term exposure above the MCL is associated with increased cancer risk and adverse reproductive outcomes. The EPA classifies total HAA5 as a probable human carcinogen at elevated concentrations. Activated carbon filtration (especially granular or block carbon) is effective at reducing HAA5. Running water through a refrigerator filter or letting it sit in an open pitcher for 30 minutes also helps, as some HAA5 species are volatile. Boiling does not remove disinfection byproducts and may concentrate them.
Cities exceeding 60 µg/L EPA MCL
HAA5 data across Hawaii
Each dot is a city with UCMR 4 HAA5 testing data. Cities where average HAA5 exceeded the 60 µg/L EPA MCL are highlighted. Size reflects population served.
Top 10 cities by haa5 level in Hawaii
All Hawaii cities ranked by haa5 level
| # | City | Level | Level | Exceeds? | Violations | Grade |
|---|---|---|---|---|---|---|
| 1 | Makawao | 34.7 µg/L | No | 83 | B+ | |
| 2 | Lahaina | 19.1 µg/L | No | 106 | B | |
| 3 | Lihue-Kapaa | 3.7 µg/L | No | 0 | A | |
| 4 | Waikoloa (Dho) | 1.6 µg/L | No | 3 | A+ | |
| 5 | Wailuku | 1.3 µg/L | No | 3 | A | |
| 6 | Waiohinu-Naalehu | 1.1 µg/L | No | 0 | A+ | |
| 7 | North Kona | 0.8 µg/L | No | 0 | A- | |
| 8 | Honolulu | 0.7 µg/L | No | 1 | B+ | |
| 9 | Pearl Harbor | 0.5 µg/L | No | 2 | A | |
| 10 | Kaneohe | 0.3 µg/L | No | 1 | A- | |
| 11 | Kekaha (Dow) | 0.3 µg/L | No | 0 | A | |
| 12 | Honolulu-Windward-Pearlharbor | 0.3 µg/L | No | 1 | A | |
| 13 | Kalaheo | 0.2 µg/L | No | 0 | A- | |
| 14 | Waipahu-Ewa-Waianae | 0.1 µg/L | No | 0 | A | |
| 15 | Schofield Barracks | 0.1 µg/L | No | 3 | A | |
| 16 | Waialua-Haleiwa | 0.1 µg/L | No | 1 | B+ | |
| 17 | Mililani Bws | 0.1 µg/L | No | 0 | A+ | |
| 18 | Hilo | 0.0 µg/L | No | 48 | A | |
| 19 | Waipio | 0.0 µg/L | No | 0 | A+ | |
| 20 | North Kohala | 0.0 µg/L | No | 0 | A- |
Frequently asked questions about haa5 in Hawaii
What is HAA5 and why does it appear in Hawaii tap water?
HAA5 (haloacetic acids) are disinfection byproducts that form when chlorine reacts with naturally occurring organic matter in source water. They are a normal byproduct of the disinfection process that makes water safe to drink. No cities in Hawaii currently exceed the 60 µg/L EPA MCL. The state average is 3.2 µg/L.
How can I reduce HAA5 exposure from Hawaii drinking water?
Activated carbon filters (granular or block) effectively reduce HAA5. Refrigerator filters and under-sink carbon systems are convenient options. Unlike lead or PFAS, HAA5 levels can also be reduced by letting water stand in an open container, as some species evaporate. Boiling does NOT remove HAA5 and can concentrate them by reducing water volume.
Which Hawaii cities have the highest HAA5 levels?
The cities with the highest average HAA5 concentrations in Hawaii are: Makawao (34.7 µg/L), Lahaina (19.1 µg/L), Lihue-Kapaa (3.7 µg/L), Waikoloa (Dho) (1.6 µg/L), Wailuku (1.3 µg/L). Note: this data is from UCMR 4 testing (2018–2020) and may not reflect current levels.