ByJohn S. McClenahen Even as "Occupational Hazards" magazine places reducing worker exposure to silica at the top of its list of challenges facing the U.S. Labor Department's Occupational Safety & Health Administration (OSHA), the Conference Board says the American workplace has become increasingly safer. From 1999 to 2002, the number of lost-time cases per 100 full-time employees among the leading U.S. firms it surveyed declined by an average of more than 40% and recorded incidents declined by an average of more than 23%, trends "generally consistent" with OSHA's statistics, says the New York-based business research group. Its report was released Jan. 27. Best practices appear to have played a part in the declines, with 84% of the companies putting them to work. According to the survey, the "essential themes" are clear management visibility and leadership; ownership of safety and health by all employees; accountability at all levels of the company; and the sharing of knowledge and information.