A study of former asbestos-exposed foundry and insulation workers was carried out in Sarnia, Ontario, home to Canada's petrochemical industry, using participatory mapping to document past exposures and subsequent diseases. Before it closed, government inspectors had monitored the use of asbestos at the facility, documenting levels that were thousands of times above the current legal limit. The study was undertaken by the Occupational Health Clinics for Ontario Workers (OHCOW) and Canadian Auto Workers (CAW) to provide evidence for worker compensation claims. Using facilitated hazard mapping, former Holmes workers graphically reconstructed their workplaces and detailed their exposures. Using facilitated body mapping, workers recorded and displayed their health problems. The study uncovered a grim pattern of occupational diseases. Following the release of the results, coupled with clinically confirmed diagnoses and corroborating evidence of exposure, hundreds of former Holmes employees and their families received compensation for occupational diseases that had previously gone unrecognized.