When limonene (a common citrus-scented ingredient in beauty products) meets chlorinated water—like in swimming pools or municipal water treatment—it breaks down into multiple chlorinated byproducts. The study found that at high chlorine ratios (above 1:10), these byproducts can form haloforms, some containing bromine. Interestingly, most of these breakdown products were actually less toxic than the original limonene in lab testing.

Researchers exposed D-limonene to chlorinated water in controlled lab conditions and used analytical chemistry to identify what chemical compounds formed. They traced the reaction pathway and tested the toxicity of the resulting byproducts.

Funding not disclosed in abstract