To develop a means for effectively utilize terpene compounds contained in tree leaves, whereby branches and leaves cut in tree thinning and pruning can be effectively utilized as a resource. For this purpose, provided are a monoterpene component-rich essential oil containing 90% or more of monoterpene components; a method for producing the monoterpene component-rich essential oil which includes subjecting coniferous leaves to microwave steam distillation and collecting a distillate thus obtained; and a method for removing environmental pollutants which includes bringing the monoterpene component-rich essential oil into contact with atmosphere containing the environmental pollutants.