More than 100 million oz. silver could be used each year in biocides for wood preservation and marine anti-fouling coatings, owing to concern over the toxicity of current, chemical-based biocides.
The United Nations has called for a ban on tributyl-tin compounds, which are used in preservative coatings for marine vessels. The proposed ban is based on the danger such compounds pose to marine life. Alternatives are being evaluated, including those based on copper, zinc and organic compounds, though silver appears to fulfil all the requirements for a marine paint biocide.
Manufacturers of preserved wood products, such as railroad ties and utility poles, have traditionally used copper arsenate in conjunction with other chemicals as a preservative. However, studies by the University of Miami in Florida show that arsenic tends to accumulate in the soil under these structures and can be harmful to people. There is also concern that the arsenic could enter aquifers used for drinking water.
Old railroad ties and utility poles containing arsenic compounds present another problem, as they can not be recycled or safely incinerated. The state of Florida has already placed a moratorium on the purchase of arsenic-containing wood products for state parks and marinas.
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