May 31, 2013
Although April temperatures seemed more like early March, the Weather Network is predicting above normal temperatures across most of southern and eastern Ontario and the southeastern corner of northeastern Ontario, as well with near normal temperatures in northcentral and northwestern Ontario.

For the landscape industry, heat requires precautions. When heat is combined with other stresses such as hard physical work, loss of fluids, fatigue or some medical conditions, illness, disability and even death may occur.

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.

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 the body overheating, causing the victim 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 usually brief in Ontario, many workers don’t have enough time to acclimatize.

A number of methods may be used by workplaces to ensure staff is healthy and safe from heat stress, including:
  • Develop, communicate and implement a heat stress plan.
  • Have a first-aid response system and trained first-aid providers in place.
  • 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, impairing the body’s response to heat. Workers on such medications should speak to their physician about working in hot environments.

Drinking water is essential to help avoid heat stress. 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.

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 has a great deal of information on heat stress. It may be found at