This is a laboratory test for 1,4 Dioxane in drinking water. According to the EPA, 1,4 Dioxane is a likely human carcinogen.

1,4 Dioxane is most often used as a stabilizer for chlorinated solvents. It is also an ingredient used in consumer products like soap, shampoo, detergent, skin cleansers, household adhesives, and liquid antifreeze.

If a person is exposed even to a low concentration of 1,4 Dioxane over their lifetime then that is likely to increase their risk of cancer.