Assembly lines with a high manual labor component pose a challenge within the framework of the Sustainable Development Goals. Fulfilling Goal 8 requires that such lines be designed not only with economic aspects in mind but also by promoting a safe and secure working environment. Under this approach, a variant of the assembly line balancing problem that limits the harmful workload assigned to stations is introduced. Two mathematical models are formulated: one limiting the number of harmful tasks per station and another limiting the proportion of cycle time allocated to harmful tasks. These models are evaluated through a case study. Results indicate that limiting the proportion of time yields better outcomes in terms of costs and productivity, while ensuring safe line configurations for workers.