How does heat affect the body?
Generally humans can control their internal temperature in the heat by sweating. However, under extreme heat and humidity conditions the body cannot keep up and will suffer from heat stress. The elderly and young children, as well as those with chronic respiratory and heart conditions, are more susceptible to heat-induced injury. Babies under one year of age are extremely sensitive to the ambient temperature, Their body temperature control is not yet mature and their temperature tends to reflect the ambient level. So special care needs to be taken with babies during hot spells.
The effect of heat on the body is a result of three factors: the humidity level, which causes 70 percent of heat stress; sun radiation, which causes 20 percent of heat stress; and the temperature itself, which causes 10 percent of heat stress. It is, therefore, important to understand that the humidity level plays the most important role in heat-induced stress and illness. During heat waves, the temperature is measured, but the humidity is also recorded and tends to bring up the temperature. This measurement is referred to as the “humidex,” a term that is short for humidity index.
About Humidex
The humidex chart(Adapted from Health Canada) below determines when people might wish to take precautions to prevent heat-related illnesses.
Humidex Degree of Comfort
20—29 No discomfort
30—39 Some discomfort
40—45 Great discomfort; avoid exertion
46 and over Dangerous; high risk of heat stroke
General recommendations for high Humidex ratings
Humidex of 35 to 39: Certain types of outdoor exercise should be toned down or modified, depending on the age and health of the individual, their physical shape, the type of clothes they are wearing, and other weather conditions.
Humidex of 40 and over, which is extremely high: All unnecessary activity should be limited.
What are the consequences of heat exposure?
Heat Exhaustion
Heat exhaustion usually occurs after prolonged exposure to heat and/or heavy exercise in the heat resulting in increased loss of body fluids through heavy sweating. The signs of heat exhaustion include
- Clammy, pale skin;
- Sweating;
- Dry mouth;
- Tiredness and fatigue;
- Headache; and
- Dizziness.
How is heat exhaustion treated?
Children suffering from heat exhaustion need to be removed from the heat immediately, given water to drink, and have cool compresses applied to their skin. Fortunately, heat exhaustion is not life-threatening, and will resolve with rest, fluids, and cooling down.
Heat Stroke
Heat stroke is a very dangerous and potentially life-threatening form of heat stress or injury. The body is so overwhelmed by the heat and humidity that it loses the capacity to sweat. This results in a very high body temperature, which in severe cases can actually cause brain damage and, tragically, even lead to death. Heat stroke can occur suddenly and is an emergency requiring immediate medical attention.
The signs of heat stroke include
- Very high body temperature—39.5° C (103° F) or higher;
- Hot, red, and dry skin;
- Absence of sweating;
- Deep or shallow breathing;
- A weak pulse rate;
- Confusion or hallucinations;
- Seizures;
- Loss of consciousness.
Prevention of heat injury
Clearly, the best approach to prevent heat injury is to limit activity during high humidex times, as heat injury can potentially result in heat stroke, which is very dangerous. Here are some ways to prevent heat injury during high humidity heat waves:
- Young children and babies should be dressed very lightly and not bundled in blankets or heavy clothing.
- Stay out of the heat and humidity by staying indoors during the hottest time of the day (usually mid-morning to mid-afternoon).
- The use of air conditioners helps … even for young babies and infants. If an air conditioner is unavailable, try to stay at the lowest level of the house, as it tends to be cooler. Also, try to keep the house as shaded as possible by closing window, blinds, and curtains. A fan will help as well.
- Do not stay or leave children in parked cars during hot weather.
- Avoid vigorous exercise in the heat (this includes children as well). If you have a young child or a child with a chronic respiratory condition such as asthma, do not allow them to partake in sporting events or exercises during heat waves, especially when there is a heat/humidity advisory in effect.
- Drink plenty of fluids. Water is best.. It is important to know that children may not feel thirsty, but will still need to drink regularly. Avoid drinking beverages containing caffeine.
- When in the sun, keep track of how long a child has been outside. Learn to recognize the signs of heat exhaustion right away, so you and your child can get shelter in order to avoid further heat injury. Also, use your common sense and remove your child from the sun and the heat as frequently as you think is necessary. Do not overdo it.
- If your children are swimming in an outdoor pool, a lake, or the ocean, you have to be aware that the high humidity and sun rays are still potential threats. Proper sunscreen protection as well as frequent rests in the shade are still necessary.
- Children are unable to perspire as much as adults and, therefore, are more prone to heat stress during exercise than adults are. A sensible approach must be used in determining if children can safely partake in sports activities during heat/humidity waves.
Smog during heat waves
Hot, humid air often carries pollutants, pollens, and moulds in higher concentrations than usual. Under these conditions, breathing this air may be harmful to younger children and children with chronic respiratory or cardiac conditions. During smog and heat/humidity alerts, be extra careful by not letting your children outside while the advisory is in effect. In Canada there is a Air Quality Health Index that reports on the air quality, depending on your location. In the United States, air quality data is reported here.