Abstract Background: Occupational noise might increase the risk of workplace injury through a variety of mechanisms. including interference with communication and increased stress. Objectives: The purpose of this study was to assess the effect of chronic noise exposure on serious workplace injury, and how the timing of exposure inuenced risk. Methods: The authors examined a cohort of 26 000 workers, who worked between 1950 and 1939. Cases were those hospitalised for a work-related injury (ICU-9 codes 800-999, and E codes E800- E999). from April 1989 to December 1998. Cumulative exposure levels were estimated for subjects based on a quantitative retrospective exposure assessment. An internal comparison of cumulative noise exposure and subchronic durations of noise exposure and injury was conducted using Poisson regression. There were 163 cases for the cumulative and 161 cases for the subchronic analysis. Results: Cumulative noise exposure were associated with a decreased risk for injuries, with the risk generally decreasing as cumulative noise levels increased, while most durations of subchronic exposure were associated with an increased risk for injury. An inverse U-shaped trend was observed with the time period of 90 days to 1 year demonstrating the most elevated RR compared with 0-1 days of exposure. Conclusions: Workers highly exposed to noise, or exposed for long periods of time. might develop effective methods of communicating the risk and preventing injuries when exposed to noise. a. Describe the 5 W's and How, if the information is given. If the information is not given, state that it is not specied. {6 marks} b. List the variables. Indicate whether each variable is categorical or quantitative. If the variabie is quantitative, give the units. (4 marks)