Why not balance this article with ‘Metal roof – runoff makes harbour toxic’?

Runoff from copper or unpainted galvanised steel roofs/guttering/downpipes contains elevated levels of Copper and zinc. Monitoring of sediments in Auckland’s Waitemata harbour show levels of these metals continue to increase, and exceed critical levels in some areas, particularly estuary areas receiving runoff from industrial areas. Modelling shows the main contributor of Zinc are galvanised iron roofs (which are extensive in industrial areas). Studies of copper roofs show they contribute dissolved an particulate coper, but are only one of the sources. Copper is widely used as an anti-foulant and sediment concentrations around marinas are very high. Shellfish are particularly senstive to Zinc and Copper.

PS Waitemata is Maori (indigenous people of NZ) for ‘Bay of Sparkling water’).