Haloacetic acids

Short description: Class of chemical compounds

Bromoacetic acid

Trichloroacetic acid

Examples of haloacetic acids

Haloacetic acids or HAAs are carboxylic acids in which one or more halogen atoms take the place of hydrogen atoms in the methyl group of acetic acid. In a monohaloacetic acid, a single halogen replaces a hydrogen atom: for example, in bromoacetic acid. Further substitution of hydrogen atoms with halogens can occur, as in dichloroacetic acid and trichloroacetic acid.

Haloacetic acids are a common contaminant in treated drinking water, particularly water subjected to chlorination.

## Contents

* 1 Contaminants in treated water
* 1.1 HAA5
* 1.2 HAA9
* 2 Health effects
* 3 Chemistry
* 4 See also
* 5 References
* 6 Further reading
* 7 External links

## Contaminants in treated water

Haloacetic acids (HAAs) are a common undesirable by-product of water treatment by chlorination. Exposure to such disinfection by-products in drinking water, at high levels over many years, has been associated with a number of health outcomes by epidemiological studies.[1]

HAAs can be formed following chlorination, ozonation, or chloramination of water, as chlorine from the water disinfection process can react with organic matter and small amounts of bromide present in water.[2] HAAs are highly chemically stable, and therefore persist in water after formation.[3]

A study published in August 2006 found that total levels of HAAs in drinking water were not affected by storage or boiling, but that filtration was effective in decreasing levels.[4]

### HAA5

In the United States, the EPA regulates the five HAAs most commonly found in drinking water, collectively referred to as "HAA5."[2] These are:

* Chloroacetic acid (MCA) (ClCH
2–CO
2H)
* Dichloroacetic acid (DCA) (Cl
2CH–CO
2H)
* Trichloroacetic acid (TCA) (Cl
3C–CO
2H)
* Bromoacetic acid (BrCH
2–CO
2H)
* Dibromoacetic acid (Br
2CH–CO
2H)

The regulation limit for these five acids combined is 60 parts per billion (ppb).[5] The sum of bromodichloroacetic acid, dibromochloroacetic acid and tribromoacetic acid concentrations is known as HAA3.[6]

### HAA9

The designation "HAA9" refers to a larger group of HAAs, including all of the acids in HAA5, along with:

* Bromochloroacetic acid (ClBrCH–CO
2H)
* Bromodichloroacetic acid (Cl
2BrC–CO
2H)
* Dibromochloroacetic acid (ClBr
2C–CO
2H)
* Tribromoacetic acid (Br
3C–CO
2H)

The level of these four acids in drinking water is not regulated by the EPA.[7] HAA6 refers to the sum of HAA5 and bromochloroacetic acid concentrations.[6]

## Health effects

Haloacetic acids are readily absorbed by the human body after being ingested, and can be absorbed slightly through the skin. At high concentrations, HAAs have irritating and corrosive properties; however, typical concentrations of HAAs found in drinking water are extremely low. HAAs are typically eliminated from the body through normal processes between 1 day and 2 weeks after ingestion, depending on the type of acid.[2]

Highly concentrated HAAs have been found to cause toxicity in various organs, including the liver and pancreas, in animal studies. This includes an increased risk of cancer, particularly of the liver and bladder. For this reason, the EPA considers a few HAAs (namely DCA and TCA) as potential human carcinogens.[2] They may also cause developmental and reproductive problems during pregnancy.[8] However, short-term adverse health effects are unlikely after ingesting dilute quantities of HAAs,[2] and the long-term low-level risks associated with drinking treated water with residual HAAs are much lower than the risks of drinking untreated water.[9]

## Chemistry

Haloacetic acids have a general chemical formula X1

C–CO
2H, where X is hydrogen or halogen, and at least one X is a halogen.

The inductive effect caused by the electronegative halogens often results in the higher acidity of these compounds by stabilising the negative charge of the conjugate base.

## See also

* Fluoroacetic acid (FCH
2–CO
2H)
* Difluoroacetic acid (F
2CH–CO
2H)
* Trifluoroacetic acid (F
3C–CO
2H)
* Iodoacetic acid (ICH
2–CO
2H)
* Diiodoacetic acid (I
2CH–CO
2H)
* Triiodoacetic acid (I
3C–CO
2H)
* Bromodifluoroacetic acid (F
2BrCH–CO
2H)

## References

1. ↑ "Drinking Water". http://cehtp.org/faq/drinking_water/drinking_water_contaminants_disinfection_byproducts_(dbp).
2. ↑ 2.0 2.1 2.2 2.3 2.4 "Haloacetic Acids (five) (HAA5): Health Information Summary". New Hampshire Department of Environmental Services. https://www.des.nh.gov/sites/g/files/ehbemt341/files/documents/ard-ehp-36.pdf.
3. ↑ "Occurrence Assessment for the Final Stage 2 Disinfectants and Disinfection Byproducts Rule". United States Environmental Protection Agency. https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1005ED2.txt.
4. ↑ Levesque, S; Rodriguez, MJ; Serodes, J; Beaulieu, C; Proulx, F (2006). "Effects of indoor drinking water handling on trihalomethanes and haloacetic acids". Water Res 40 (15): 2921–30. doi:10.1016/j.watres.2006.06.004. PMID 16889815. Bibcode: 2006WatRe..40.2921L.
5. ↑ "Disinfection Byproducts: A Reference Resource". United States Environmental Protection Agency. https://archive.epa.gov/enviro/html/icr/web/html/gloss_dbp.html.
6. ↑ 6.0 6.1 "Haloacetic acids (HAAs) - Environment and Climate Change". https://www.gov.nl.ca/ecc/waterres/drinkingwater/haa/.
7. ↑ Stanford, Ben (16 September 2025). "Impact of Haloacetic Acid MCL Revisions on DBP Exposure and Health Risk Reduction" (in en). https://www.waterrf.org/research/projects/impact-haloacetic-acid-mcl-revisions-dbp-exposure-and-health-risk-reduction.
8. ↑ "Haloacetic Acids in Public Water and Health". Iowa Department of Public Health. https://tracking.idph.iowa.gov/Environment/Public-Drinking-Water/Public-Water-and-Health/HAA5-in-Public-Water-and-Health#:~:text=Haloacetic Acids are a family,substances in the source water..
9. ↑ "Disinfection byproducts: HAA5" (in en-US). Minnesota Department of Health. https://data.web.health.state.mn.us/haa5-messaging.

## Further reading

* ANSI
* National Institute of Health

## External links

* Haloacetic Acids (For Private Water and Health Regulated Public Water Supplies)
* "Drinking Water Contaminants – Standards and Regulations". US Environmental Protection Agency.

0.00

(0 votes)

Original source: https://en.wikipedia.org/wiki/Haloacetic acids. Read more

|

Retrieved from "https://handwiki.org/wiki/index.php?title=Chemistry:Haloacetic_acids&oldid=4357423"