Haloacetic Acids (HAAS)
HAA5·Affects liver, reproductive
A regulated family of five disinfection byproducts that form alongside THMs when chlorine reacts with organic matter. The EPA caps the combined total at 60 ppb.
HAA5
EPA limit
0.060 mg/L (HAA5 combined)
Most at risk
Long-term consumers, pregnant women
Found in
City water
AquaOx filters
YesActivated coconut shell carbon
What it does to you
Health effects
HAA5 is the EPA's regulatory grouping of five haloacetic acids: monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), monobromoacetic acid (MBAA), and dibromoacetic acid (DBAA). The group is regulated together at 60 ppb because the individual species behave similarly and rarely occur in isolation.
The liver is the primary target organ across the group. DCAA and TCAA are classified by the EPA as likely human carcinogens based on liver tumors in long-term animal studies. Reproductive and developmental concerns are the second major axis: animal data show adverse developmental outcomes, and human epidemiology of long-term chlorinated-water consumers shows weak signals for bladder cancer and adverse reproductive outcomes.
HAAs are non-volatile, so inhalation and shower-vapor exposure are not the dominant routes (unlike THMs). The MCL is designed around lifetime ingestion through drinking and cooking water.
Where it comes from
How it gets into your water
HAAs form when chlorine added at the treatment plant reacts with naturally-occurring organic matter (humic and fulvic acids from leaves, soil, algae). The same reaction produces THMs; the ratio of HAAs to THMs depends on water chemistry, pH, and source-water characteristics.
The mix between the five HAA5 species depends on bromide content in the source water: low-bromide supplies tend toward DCAA and TCAA, while higher-bromide supplies shift toward the brominated species. The reaction continues in distribution pipes, so levels are generally higher at the end of the line than near the plant.
Chlorinated treatment plants
Chlorine reacts with organic matter
Distribution pipes
Reaction continues during transit
Tap water
Ingested in drinking and cooking water
Find out for yourself
Is it in your water?
If your home is on a chlorinated municipal supply, HAAs are in your water. Every utility tests HAA5 and reports the running annual average in its Consumer Confidence Report (CCR). Well-run utilities run comfortably below the 60 ppb MCL, but levels vary by season and by your position in the distribution network.
Concentrations typically peak in late summer and early fall when source-water organic content and water temperatures are highest. Well-water households generally do not have HAAs unless the well is regularly shock-chlorinated.
The fix
How AquaOx filters it
HAAs adsorb readily onto activated carbon. The catalytic and coconut-shell carbon stages in AquaOx systems capture the full HAA5 family at residential flow rates.
Because HAAs are non-volatile, ingestion is the main exposure route, so a point-of-use filter on the kitchen tap also addresses the dominant exposure. The advantage of AquaOx as a whole-house system is consistent filtration across every fixture: kitchen, ice maker, coffee maker, formula-mixing station.