Disinfection Byproducts in Miami Water: TTHMs and HAA5 Explained
Disinfection byproducts form when the chlorine used to kill germs reacts with natural organic matter in water. The two main groups are total trihalomethanes (TTHMs) and five haloacetic acids (HAA5). EPA limits them to 80 and 60 parts per billion. Miami-Dade's 2025 averages were 50 ppb TTHM and 34 ppb HAA5, under the limits, and carbon filtration reduces both.
How They Form
Disinfection is one of public health's biggest wins. It's why tap water doesn't spread cholera or typhoid. The trade-off is that chlorine reacts with leaves, soil and other organic matter in source water. South Florida's water is naturally rich in organic material, so managing byproducts is an ongoing job. Miami-Dade's use of chloramine helps keep byproducts lower as water moves through the pipes.
The Limits and the Local Numbers
Under EPA's Stage 2 Disinfectants and Disinfection Byproducts Rule, utilities must keep the running annual average at each monitoring site under the limits.
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TTHMs: EPA limit 80 ppb. Miami-Dade WASD 2025 average 50 ppb. Homestead 2025 average 39.5 ppb.
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HAA5: EPA limit 60 ppb. Miami-Dade WASD 2025 average 34 ppb. Homestead 2025 average 19.5 ppb.
Sources: the WASD 2025 Water Quality Report and the City of Homestead 2025 Water Quality Report.
Why People Choose to Reduce Them
EPA's limits are based on long-term exposure, and some people want lower levels anyway, especially in drinking water. TTHMs can also evaporate in a hot shower, so whole-home filtration reduces what you breathe in too.
How to Reduce Them at Home
Whole-home carbon filtration reduces TTHMs and HAA5 at every tap and shower. See the Hydronex iGen C. Reverse osmosis at the kitchen sink adds another layer for drinking and cooking water. See the Micromax 8500.
Does Boiling Help?
Boiling releases some TTHMs into the air but doesn't remove HAA5, and it concentrates other dissolved substances as water evaporates. Carbon filtration is more reliable.
Common Questions
Are TTHMs in Miami water dangerous? Miami-Dade's 2025 average of 50 ppb is under EPA's 80 ppb limit. Carbon filtration lowers them further if you prefer.
Why not stop disinfecting? Disinfection prevents waterborne disease. The goal is to keep it while keeping byproducts low.
What are TTHMs? Total trihalomethanes are a group of four chemicals, including chloroform, that form when chlorine reacts with natural organic matter in water.
What is HAA5? HAA5 is the total of five haloacetic acids, another group of disinfection byproducts that EPA regulates.
Does a pitcher filter remove TTHMs? Some carbon pitcher filters are certified to reduce them, but check the specific cartridge's NSF certification.
Can I breathe in disinfection byproducts in the shower? Yes. TTHMs can evaporate in hot shower water. Whole-home carbon filtration reduces exposure at every tap and shower.