FRAMINGHAM (11/03/2003) - Silicon Valley owes its might to clean-room workers such as James Moore and Alida Hernandez who worked for IBM Corp. in the 1970s and 1980s. They worked in one of Big Blue's clean rooms - manufacturing facilities that used powerful chemicals to keep computer components free of contaminants. This week, a jury trial begins to determine whether the work caused health problems that almost killed them. The trial will set the stage for more discussion about whether clean-room work has sickened thousands of other semiconductor manufacturing employees. Because of automation and increased awareness, current conditions are thought to have improved. But no comprehensive study of the long-term effects of working in a clean room has been undertaken, partly because the industry has been unwilling to supply the necessary data, critics say. The trial will focus on whether IBM withheld data that workers were suffering from higher rates of cancer and birth defects than normal segments of the population. IBM denies any wrongdoing.