JAMES CARLIN WATCHED A SMALL AIRPLANE snake over the field beyond the barbed wire fence at Deuel Vocational Institution, a state prison in Tracy, about 60 miles east of Berkeley. He’d seen the plane before. It came at daybreak, flying low and trailing behind it a plume of chemicals. As his years in prison passed, Carlin began to notice a pattern. Each time the plane came, red bumps blistered the skin of the men lifting weights on the yard. Carlin had read environmentalist Rachel Carson; he thought the chemicals and the rashes must be related. Then it got worse.