There are five haloacetic acids (HAA5) that occur as a by-product of water treatment using chlorination. The five acids are monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid. Additionally, HAAs are not affected by boiling or storage. However, filtration is effective in decreasing their levels.

For some people, drinking water with elevelated levels of HAAs can lead to a higher risk of cancer, reporoductive issues, rectal issues, fetal growth, and adolescent development.