May 15, 2012
When heat is combined with other stresses such as hard physical work, loss of fluids, fatigue or some medical conditions, it may lead to heat–related illness, disability and even death.

Heat exposure is a concern for those in the landscape industry. Direct sunlight is usually the main source of heat, but humidity also contributes to heat stress.

It is recommended that outdoor workers develop a workplace heat stress prevention plan. Some helpful tips to get you started, will help take the next step in keeping this summer safe and healthy for everyone on your crew.

Heat stress can take many forms, depending on the severity of external and internal factors and the condition of the individual. A worker expending large amounts of physical energy in a hot and humid environment, without regular rest or water breaks, may eventually experience heat exhaustion, fainting, heat stroke or heart attack.

The five symptoms of heat stress are heat rash; fainting; muscle spasms in stomach, legs, arms; heat exhaustion, which resembles shock (feeling of faintness/nauseated, low blood pressure, skin may be hot and red, victim may have a fever); and body overheats, with victim experiencing mental confusion and needing immediate medical attention.

It takes seven to 14 days of continuous exposure to heat for the body to adjust to high temperatures. Because extended periods of extreme temperatures are so brief in Ontario, many times workers don’t have enough time to acclimatize.

Best approach

Eliminate heat stress by preventing the warning signs from happening. There are lots of ways workplaces can take measures to ensure their staff is healthy and safe from heat stress, including:
  • Develop, communicate and implement a heat stress plan for all workers.
  • Have a first-aid response system and trained first-aid providers in place in the event it does occur.
  • Policies for the recording and reporting of incidents should be developed and made available.
  • Provide air-conditioned rest areas or put up shade barriers to block sun heat.
  • Increase the frequency and length of rest breaks.
  • Provide cool drinking water near workers and remind them to drink a cup every 20 minutes or so.
  • Consider the types of clothing employees wear and if adjustments can be made in hot weather.
  • Set-up a thermometer and humidity meter.
  • Measure and monitor the Wet Bulb Globe Temperature (WBGT). The WBGT is a composite temperature used to estimate the effect of temperature, humidity, wind speed and solar radiation on humans.
  • Workers on medication or with pre-existing medical conditions may be more susceptible to heat stress as some medication may impair the body’s response to heat. These workers should speak to their personal physicians about work in hot environments.

As for drinking water, do not to wait until you’re thirsty because by that point you’re already dehydrated. Workers should drink water on a regular basis, even if they don’t feel thirsty.

The common assumption is people with lots of risk factors are going to succumb first. In fact, it is usually young males, the least suspected, who end up ignoring their body’s signals. Workers need to listen to their own bodies and take precautions.

Legal requirements

Employers have a duty under section 25(2) (h) of the Occupational Health and Safety Act to take every precaution reasonable in the circumstances for the protection of a worker. This includes developing hot environment policies and procedures to protect workers from hot weather.

The Ministry of Labour recommends reading the Threshold Limit Values (TLVs) for Heat Stress and Heat Strain published by the American Conference of Governmental Industrial Hygienists (ACGIH).