This article first appeared in Canadian Occupational Safety magazine's Problem Solvers column.

Question: I am the new manager of a small landscaping business. My crew and I will be working mostly outdoors, and this summer promises to be a hot one. Should we be concerned about heat stress?

Answer:

To work safely in hot weather, it helps to understand how the human body responds to the combination of heat and moderate to heavy physical work, as in groundskeeping.

A healthy body maintains a steady temperature of approximately 37°C, through a dynamic balance of heat production from muscle work, and heat loss from sweating. When this balance is upset and the body can no longer cool itself properly, a number of heat-related health problems may occur.

The solution may seem obvious and simple: to avoid overheating, cool yourself down. Nevertheless, compensable cases of time-loss still occur every year in Canada from heat stroke, sunstroke, heat cramps or heat exhaustion. In temperatures above the thermal comfort zone, often with the added perils of humidity, slow wind speed and a lack of shade, many outdoor workers find it difficult to escape the heat.

BASIC PRINCIPLES OF WORKING IN HOT ENVIRONMENTS

Reduce exposure to the sun.

If possible, it is a good idea to erect temporary shelters or move some tasks indoors or in the shade. At the very least, workers should take advantage of rest breaks to get out of the sun. They should also protect their eyes, with sunglasses that meet Canadian Standards Association (CSA) standard Z94.5-95.

Sunblock with a SPF of at least 15 is commonly recommended for protecting the skin from the sun's harmful rays; unfortunately it also blocks the pores of the skin, restricting perspiration and evaporation (see below). Clothing and shade are the best sun protection.
Skin cancer from sunlight is an important concern, and a whole other topic (see Resources).

Allow the body to perform its natural cooling functions.

Sweating is the body's most effective cooling mechanism. The cooling occurs as sweat evaporates. Working shirtless or hatless defeats that process; the sun dries sweat too quickly and prevents it from cooling the body. Outdoor workers should wear loose-fitting clothes made of a light fabric that "breathes." Clothes give sweat a chance to cool the body and help protect the skin.