A former tribal official says he thought asbestos-laden building materials had been removed from an old plywood mill that was converted into The Mill Casino in 1995.Through his attorneys, Bruce A. Anderson told jurors in U.S. District Court in Portland in mid-June that environmental experts and government officials told him many times that the hazardous asbestos had been properly disposed of. Anderson said he didn't learn of workers' exposure until federal agents began a criminal investigation in 1996. Anderson, responsible for overseeing conversion, was charged last year with six environmental crimes for allegedly failing to notify authorities about wallboard that contained as much as 60 percent asbestos. Other charges included improperly removing the material and illegally disposing of it. He faces an additional count of lying to a U.S. Environmental Protection Agency investigator. The trial is expected to last about two weeks. In 1971, the government determined asbestos dust is a hazardous air pollutant and breathing it can cause severe health problems. The EPA set strict removal and disposal protocols for any construction material containing more than 1 percent asbestos. One of Anderson's attorneys said Anderson was not in charge of day-to-day demolition of the mill and was not an expert in environmental cleanup.