When limonene (a common fragrance ingredient in beauty products) mixes with chlorinated water—like in swimming pools or treated tap water—it breaks down into multiple chlorinated byproducts through a chain reaction. The study found that most of these byproducts are actually less toxic than limonene itself, though at high chlorine levels, potentially harmful haloforms can form.

Researchers conducted lab experiments exposing D-limonene to chlorinated water under controlled conditions, then analyzed what chemical compounds formed using electron ionization to identify the structures.

Funding not disclosed in abstract