Can an anchor be "environmentally friendly?:

[Robertcateran]

Aluminium toxicity happens at certain pH water when a change in pH in the gills causes the Aluminium compounds to drop out and clog the gills. There is plenty of aluminium naturally in many freshwater waterways. Mucking around with the pH is what causes the problem. In the Ocean, the pH is so much higher it is never a problem. I can't see either lead or aluminium being much of a problem in the ocean, but in anoxic mud in harbors it may be possible to dissolve and enter the food chain.
Robert