Health & Safety Publication

A Publication of the Workers Health & Safety Centre – June 20, 2012

Finding relief from heat, humidity and ultraviolet radiation

For many, the arrival of summer is cause for celebration. For others, including workers and employers, it can be cause for concern.

Heat, whether from the sun or other sources in a workplace, can place undue stress on the body's natural cooling system. High humidity and excess physical work adds to this undue stress.

Common symptoms of heat stress include feeling faint, dizzy and weak and/or experiencing rapid breathing and headache. Heat cramps, extreme weakness and dizziness and vomiting are additional warning signs. Heat stroke is the most serious consequence and can lead to permanent damage, even death.

Workers at risk can include those employed in the construction industry, public works, farming, landscaping, emergency response services and other outdoor jobs. Working in hot and/or humid indoor environments such as bakeries, commercial kitchens, laundries, factories and warehouses can also be dangerous.

In addition to the risk posed by heat, outdoor workers are also exposed to the sun’s ultraviolet (UV) radiation. Exposure can damage the eyes and can lead to sunburn and skin cancer.

According to the Occupational Health & Safety Act (the Act), employers must take reasonable precautions to protect workers. This should include developing a heat stress (and harmful UV ray exposure) prevention and monitoring policy along with procedures to implement this policy. Both the policy and procedures should be developed in consultation with the joint health and safety committee or worker representative. An essential element of a heat stress program must be worker and supervisor training.

With respect to enforcing the Act’s “reasonable precaution” duty, MOL inspectors rely on threshold limit values (TLVs) for heat stress published by the American Conference of Governmental Industrial Hygienists (ACGIH).

The Occupational Health Clinics for Ontario Workers (OHCOW) offers resources to help focus workplace efforts on prevention, including a sample Humidex/Heat Stress Response Plan based on the ACGIH TLVs. OHCOW also offers a Humidex-Based Heat Stress Calculator on their web site (see link below).

With the summer now here, there’s no time like the present to perform a health and safety audit to ensure your workplace has implemented the strategies needed to eliminate the risk to worker health posed by heat, humidity and UV rays.

For our part, the Workers Health & Safety Centre has published a heat stress fact sheet and we offer Heat Stress Training focusing on general awareness along with workplace specific prevention strategies.

Want to know more about the WHSC Heat Stress Training—call 1-888-869-7950 or contact a WHSC near you and ask to speak to a training service representative?

Want to read the WHSC Heat Stress: Cool Solutions fact sheet?

Want to access workplace heat stress assessment tools developed by OHCOW?

Want to read the OHCOW publication Hazards of Working in the Sun?