English word polychlorinated comes from English chlorinated, English poly- (Many. Polymer.)

Detailed word origin of polychlorinated

Dictionary entry	Language	Definition
chlorinated	English (eng)	(chemistry) Of water, that has had chlorine added to it to purify it.
poly-	English (eng)	Many. Polymer.
polychlorinated	English (eng)	(chemistry) Having many hydrogen atoms replaced by chlorine.

Words with the same origin as polychlorinated