[Bob]

Of the 100 products tested, 47 had detectable levels of 1,4-dioxane...

And if the test were more sensitive, the rest probably would as well. Without further data, the term detectable just means that the level is above the sensitivity threshold of the current testing method.

[Old Professer]

Which could be as small as 4PPT.

That would be roughly one drop in 900,000 gallons of water.