Clopyralid

Clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) is a selective herbicide used for control of broadleaf weeds, especially thistles and clovers. For control of Seattle, USA, clopyralid was widely used for weed control in lawns until prohibited in 1999. There, a city-mandated curbside grass clipping collection and composting program produced compost with measurable levels of clopyralid. Subsequently, DowAgro, the manufacturer of clopyralid, voluntarily deregistered it for lawn uses.

The deregistration was viewed by some as a triumph of grass-roots activism in the face of corporate and governmental lies. Others saw it as an exaggerated, politically correct response to isolated incidents with no basis in science.