Science Questions

Some roofs have clean lines across them caused by copper cables that have been lain across them in the past, and I've also heard that to kill a tree, you can drive a copper nail in to the trunk. In both cases, copper seems to have bad effects on living organisms, including trees and algae. Are the copper water pipes we have in our houses likely to have a similarly bad effect on humans, just as lead pipes did ? Rob

Plants make food for themselves via photosynthesis. This process involves a number of chemicals, enzymes and pigments, including green chlorophyll. Copper stops the photosynthetic process from working, which is why copper is toxic to plants and algae. The lines on the roof are likely to have been caused by copper: some builders purposely build copper strips into roofs to stop them going green. As for killing a tree with a copper nail, I'm not sure that that is true. Trees are very large and contain lots of water to dilute any copper particles put into it. Therefore, lots of copper would be needed to kill a tree. Metallic copper (which a nail would be made from) does not go into solution easily and would find it hard to get into the tree's food and water transport systems. In terms of humans, I think copper poisoning is unlikely in this area. The east of England has very hard water, which makes the water pipes fur up. This makes it hard for our drinking water to come into contact with the pipes. Copper in small amounts is actually important for humans as it helps some of our enzymes work. Only in the genetic 'Wilson's disease' can copper be a problem where sufferers accumulate too much of the metal in their brains.

December 2004