Extreme heat impact on workplace injury rates

Research indicates that extreme heat serves as a significant, indirect driver of workplace injuries by impairing cognitive functions such as attention, balance, and judgment.

In Canada, a mid-July heat wave with humidex readings reaching 45°C in southern Ontario and western Quebec coincided with studies showing that injury rates in Quebec climb by approximately 0.2% for every 1°C increase in daily maximum temperature. This risk affects both indoor and outdoor sectors, including construction, agriculture, and manufacturing.

Data from the United States suggests a similar trend, with research estimating that extreme heat contributes to roughly 28,000 additional workplace injury cases annually. Heat is described as an ‘invisible stressor’ that can slow reaction times and increase mental fatigue, leading to accidents such as falls and vehicle crashes.

Beyond physical safety, heat exposure is emerging as a growing source of corporate liability. In the U.S., the Postal Service was previously fined by OSHA following a heat-related death of a mail carrier. While the International Labour Organization recognizes the right to safe working environments, federal protections remain limited in certain regions. Consequently, labor unions are increasingly utilizing occupational heat as a strategic lever in organizing campaigns, highlighting inadequate safety policies to pressure corporations into adopting more robust heat-mitigation standards.