HAA9 (nine haloacetic acids)
Overview
HAA9 is the sum of nine haloacetic acids, the full group that forms when a disinfectant meets organic matter in water. Only five of the nine are regulated, as HAA5. The other four are not, so a utility can meet the HAA5 limit while carrying more of the group than that limit describes. EPA monitored HAA9 nationwide in 2018 to 2020 and has set no limit for it.
In Florida, HAA9 (nine haloacetic acids) was found in 250 community water systems serving about 19,989,753 people. Nobody has set a legal limit for it, so no reading here counts as an exceedance and no utility is required to do anything about it.
Where it comes from: Byproduct of drinking water disinfection, formed in the water itself.
The standards
Enforceable. A utility must stay at or under this.
Health-based, not enforceable. Often lower than the limit, sometimes zero.
Nobody has published a health goal for haloacetic acids as a total. California has published one for each acid the totals count: dibromoacetic acid 0.03 ppb, trichloroacetic acid 0.1 ppb, dichloroacetic acid 0.2 ppb, monobromoacetic acid 25 ppb and monochloroacetic acid 53 ppb, all issued 2022. Florida Water Report reads the total against the strictest of them. EPA's own health goal for dichloroacetic acid is zero. Source: California State Water Resources Control Board, MCLs, DLRs and PHGs for Regulated Drinking Water Contaminants, updated September 2025.
Health effects the EPA associates with it: EPA published no reference concentration for HAA9 in its national survey, so there is no federal number to compare a reading against. The regulated subset of five is limited at 60 ppb, a figure that covers five of these nine and says nothing about the rest.
The health goal is set on health alone. The legal limit is set as close to it as is technically and economically feasible, so treatment cost and available technology are written into the number a utility is measured against. A system at or under the limit is meeting the standard it is required to meet. Both numbers are shown so the distance between them is visible.
What removes it
The group forms in the water, so removing it at home means activated carbon after the fact. At the plant it is controlled by taking out the organic matter before the disinfectant is added.
Treatment guidance describes the methods generally used for this contaminant. What your own tap actually carries depends on your plumbing and your service line as much as on the utility, which is what a test at the house tells you and an annual report cannot.
Where in Florida
Highest reported levels
Showing the 25 highest of 250 systems that reported HAA9 (nine haloacetic acids).
Data Sources
These figures describe water as delivered by each utility, not what your home’s plumbing adds after it arrives. Informational; not a substitute for testing your own tap.