Designers and managers of recycling processing plants need to be informed about the inherent occupational health and safety risks; however, there are few studies in the literature describing these risks. Therefore, the objectives of this project were to document the biological, chemical, physical, and ergonomic risks in three household-waste recycling plants. Bioaerosols (molds and bacteria) were measured using the methodology recommended by the American Society for Testing and Materials (ASTM). Chemical contaminants and physical agents suspected of being present in this type of environment were measured using the standard methods of the Quebec Occupational Health and Safety Research Institute (IRSST). The ergonomic part of the study identified the work requirements and risk factors causing the workers' physical symptoms. In summer, the average concentrations of total bacteria were greater than the Scandinavian guideline of 10,000 colony forming units per cubic meter of air (CFU/m3) in the receiving areas in plants 1 and 3, in the sorting areas of the three plants, and in shipping in plants 1 and 3. When the average concentrations of gram-negative bacteria were compared to the Scandinavian guideline of 1000 CFU/m3 of air, only the sorting department in plant 2 in summer exceeded this value. Average indoor concentrations of molds that were statistically significantly greater than those measured in the upwind outdoor air were measured in all departments in plants 1 and 3, regardless of the season, and only in sorting in plant 2 during the summer. The only chemical contaminant measured at average concentrations greater than 50% of the Threshold Limit Values (TLVs) proposed by the American Conference of Governmental Industrial Hygienists (ACGIH) was CO in the sorting departments in plants 1 and 2 during the winter. Noise exceeded the ACGIH TLV in plant 2. The workers' physical symptoms seem to be caused by the posture and effort required while remaining in a stationary position. Action must be focused on improving aspects such as work organization and personal protection and on informing citizens of the need for cleanliness of the material to be recycled.