Is it dangerous to swim in water with oil in it?

In general, yes.

The sometimes iridescent "oil film" seen on water surfaces may be crude oil, which is modestly toxic to people; used motor oil, which is much more toxic and carcinogenic; gasoline, which is carcinogenic (especially premium unleaded grades); or other hydrocarbon subsances that may be poisonous or unhealthful. There are other film-forming substances that may appear on water, that may be harmless, but a swimmer won't be able to differentiate these from the toxic slicks.


If oil films or slicks are seen, it is best not to swim in or drink the water. If swimming or drinking are unavoidable, stay away from the oil slick, or pour it off before drinking. Make every effort to avoid inhaling or swallowing the slick material. If the oily material gets on the skin, bathe with mild dish detergent (such as Palmolive) to remove it. If swallowed, take 2-3 tablespoons of mineral oil by mouth, which should eliminate the material from the system, and consult a health practitioner if available.