Pesticides leach from building facades

Construction materials such as paint, plaster and roof sealants are an under-appreciated source of water pollution, claim scientists at the Swiss Federal Institute of Aquatic Science and Technology (Eawag).

The research uncovers a new source of urban water pollution that may contribute to breaches of EU drinking water standards. The 1998 drinking water Directive sets a limit of 0.1 micrograms per litre for any individual pesticide active ingredient and a 0.5 µg/l limit on total pesticides.

Herbicides and fungicides are added to outdoor materials to prevent fouling. The Swiss researchers tested runoff from facades under laboratory conditions, as well as on an outdoor experimental building and several new buildings in the Zurich region.

Pesticide concentrations were especially high after rain fell on newly painted or rendered houses, in one instance reaching 7,000µg/l of the herbicide diuron in the first litre of runoff.

Measurements from a local river found 22 pesticides in concentrations exceeding 0.1µg/l. Many of the compounds are likely to be from urban sources because they are prohibited for agricultural application or were not found at times typical of farm use.