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Not health advice. Contact your local water utility for concerns.
Data from EPA Water Quality Reports. For official information, contact your water utility or health department.
Analysis of total trihalomethanes (tthm) contamination levels across Hawaii cities
These cities have total trihalomethanes (tthm) levels above 50% of the EPA limit but within compliance
Complete list of cities where total trihalomethanes (tthm) has been detected, sorted by level
| City | Level | EPA Limit | % of Limit | Status |
|---|---|---|---|---|
| KaneoheGrade C+ | 47.53 ug/L | 80.00 ug/L | 59.4% | Warning |
| HonoluluGrade B- | 42.52 ug/L | 80.00 ug/L | 53.2% | Warning |
| Pearl CityGrade B- | 29.91 ug/L | 80.00 ug/L | 37.4% | Safe |
| MakakiloGrade B- | 22.64 ug/L | 80.00 ug/L | 28.3% | Safe |
| HiloGrade A- | 17.59 ug/L | 80.00 ug/L | 22.0% | Safe |
| East HonoluluGrade A- | 16.38 ug/L | 80.00 ug/L | 20.5% | Safe |
| KahuluiGrade B+ | 15.42 ug/L | 80.00 ug/L | 19.3% | Safe |
| Mililani TownGrade A- | 14.08 ug/L | 80.00 ug/L | 17.6% | Safe |
| WahiawaGrade A- | 8.92 ug/L | 80.00 ug/L | 11.1% | Safe |
| WaimaluGrade A | 8.75 ug/L | 80.00 ug/L | 10.9% | Safe |
| KailuaGrade B+ | 4.78 ug/L | 80.00 ug/L | 6.0% | Safe |
| KiheiGrade B+ | 4.34 ug/L | 80.00 ug/L | 5.4% | Safe |
| Ewa GentryGrade A- | 3.87 ug/L | 80.00 ug/L | 4.8% | Safe |
| WaipahuGrade B+ | 1.86 ug/L | 80.00 ug/L | 2.3% | Safe |
| Mililani MaukaGrade B+ | 0.011 ug/L | 80.00 ug/L | 0.0% | Safe |
Trihalomethanes are disinfection byproducts formed when chlorine reacts with organic matter in water. Long-term exposure to high levels of TTHMs has been associated with increased cancer risk, particularly bladder cancer. Studies have also linked TTHMs to reproductive problems including miscarriage and birth defects. Chloroform, the most common THM, can cause liver and kidney damage.
Formed when chlorine disinfectants react with natural organic matter in water; higher in surface water systems with more organic material
Based on our analysis of EPA Safe Drinking Water Information System (SDWIS) data and local water utility reports,total trihalomethanes (tthm) has been detected in 15 Hawaii water systems. The average level across all tested cities is 20% of the EPA Maximum Contaminant Level (MCL), with the highest detection at 59.4% of the limit.
The EPA MCL for total trihalomethanes is 80 ug/L (80 ppb). The EPA MCL for total trihalomethanes (tthm) is 80 ug/L. This limit is set to protect public health based on available scientific evidence about the contaminant's health effects.
15 Hawaii cities have total trihalomethanes (tthm) detected in their water supply. All tested cities are within EPA safety limits.
Increased cancer risk (bladder), liver and kidney damage, potential reproductive effects. The most vulnerable groups include pregnant women and people with liver disease.
The most effective methods for removing total trihalomethanes (tthm) include Activated Carbon, Reverse Osmosis. Look for filters certified by NSF/ANSI for total trihalomethanes (tthm) reduction.
The EPA Maximum Contaminant Level (MCL) for total trihalomethanes (tthm) is 80 ug/L.The EPA MCL for total trihalomethanes is 80 ug/L (80 ppb).
Recommended filtration methods for total trihalomethanes (tthm) removal:
Very effective for TTHMs
Removes 90%+ of TTHMs
THMs are volatile and can be removed by aeration