The white powder in treated pine is Sodium Sulphate, a harmless substance which, if necessary, can be simply brushed or hosed off.
Sodium sulfate (also known as sodium sulphate or sulfate of soda) is the inorganic compound with formula Na2SO4 as well as several related hydrates.
All forms are white solids that are highly soluble in water.
With an annual production of 6 million tonnes, the decahydrate is a major commodity chemical product.
Sodium sulfate is used in a variety of industrial processes.
It is employed in the manufacture of detergents, glass, and textiles.
It also serves as a drying agent (desiccant) in laboratories, and as a laxative in the medical field.