CCA stands for chromated copper arsenic. CCA is a wood preservative, which is in use since 1930. copper is the protective structure and arsenic is the insecticide used. Arsenic serves no purpose in protecting the timber, but it is the binding agent of other 2 chemcals. The best argument in terms of science would be , not to remove CCA- treated wood from the existing building structure. this wood preservative was banned due pressure from common and not scientific reason. The concern was on arsenic exposure. The exposure level of arsenic from the treated wood is far below fatal levels , than it could be seen in diet and drinking water. Hence doesn't harm children. A research also shows that after 45 years of treatment the exposure level is almost nil. Hence it is safe to have a CCA treated woods at home.