The current record temperatures for Australian CBD’s are 43.2°C in Brisbane, 46.4°C in Melbourne, 40°C in Sydney, 44.5°C in Perth, and 40.4°C in Darwin2. Temperatures are just part of the equation; you also need to factor in humidity, airflow, radiant heat, thermal mass and the greenhouse effect. Interestingly, in 2009 RACQ surveyed the temperature relationships between the inside and outside of a vehicle and found temperature had doubled after 20minutes and continued to increase over time1 (outdoor average 32.5°C and sealed vehicle ambient temperature 75.1°C).
In hot conditions workers will instinctively remove clothing, find shade, drink more, and find moving airflow. However work conditions are not always conducive to workers being able to remove themselves from heat hazards. They might need to dress in PPE, be unable to leave their machines, and work to tight schedules. So lets look at what happens to our bodies when experiencing these high temperatures.
Physiology of heat stress:
Our bodies try to keep our temperature steady at 37°C and the osmolarity of the fluid between 285-295 milli-osmoles per kilogram. If the external environmental conditions are challenging, then the body will go into action. Involuntary heat defenses kick in with the process of sweating. It uses the effect of evaporative cooling. When the water (sweat) evaporates it effectively cools the skin. This is actually quite an efficient process but the effect is severely reduced in humid conditions. Sweating drastically loses water and salt content from the body, especially over extended periods.
The body carefully regulates the internal chemical composition of our blood and plasma. If the salt concentration in the blood increases the kidneys will try and produce concentrated urine (high salt, low water) to restore balance. This results in thick, yellow urine. Workplaces often have posters displayed in bathrooms showing different urine colour, their meanings and reminders to drink. We need to question how effective urine colour charts might be when a dehydrated worker may only visit the bathroom once in a workday?
Where it goes wrong:
Uncontrolled heat exposure means that the body will lose water through sweating, fluid concentrations then change, core temperature increases and organs (including the brain) start to fail. The process can occur quickly and can have dire consequences.
What to look out for:
Even mild heat stress and dehydration can cause a myriad of symptoms including; nausea, dizziness, clumsiness, weakness, fainting, cramping, rashes, headaches, poor concentration, irritability, and worsening of pre-existing medical conditions. Heatstroke and in the extreme, death, can occur when symptoms are not quickly and properly managed.
So what can you do?
Employ Health’s top tips on the day3:
Prevention top tips:
If there are any heat risks then the hazards must be managed. Health professionals such as occupational physiotherapists have studied physiology and can assist you with any further questions you might have. If you would like any further resources please get in touch.
1 RACQ Temperature in cars survey 2009
3 www.worksafe.vic.gov.au Guidelines for working in heat 2013