Chapter 8 - Alcohol

Learning Outcomes

After reading through this chapter, you should be able to:

  • Discuss the effects alcohol has on alertness.
  • Discuss the effects alcohol has on sleep.
  • Explain how alcohol consumption affects performance.

What is alcohol?

Alcohol is known to significantly impair performance at moderate and high levels of intoxication. Alcohol intoxication greatly affects the way you respond and interact with your environment and increases your risk of having an accident.

In many industrialized countries, workplaces require a zero blood alcohol concentration (BAC) for their employees. The Canadian Aviation Regulations demand that air crews not drink alcoholic beverages within eight hours of flying. In most working environments, employers cannot tell employees how much alcohol they are allowed to consume away from work. In order to be well rested and fit for work, you need to understand how alcohol works and how it influences sleep and alertness.

Alcohol is the second most widely consumed drug after caffeine. Alcohol is legal in most countries and is so common that it is easy to forget that it is a drug and that it can be dangerous if not used sensibly.

Alcohol is a central nervous system depressant. In small doses, it can make you feel more relaxed and less inhibited. In larger doses, it makes you drunk and impaired.

Alcohol reduces:

  • environmental awareness
  • responses to sensory stimulation
  • mental functioning
  • physical activity.

In high doses, alcohol can produce:

  • increased drowsiness
  • lethargy
  • amnesia
  • hypnosis
  • anaesthesia

Alcohol intoxication is one of the major causes of road accidents. Most countries have laws restricting people with a BAC above a certain level from driving, working, or operating dangerous equipment. In Canada, a BAC of 0.08% or higher means that driving is prohibited. Many activities in the aviation field have a zero alcohol tolerance.

Accident risk

The table below details the effects of various blood alcohol levels. Alcohol progressively impairs your ability to perform and dramatically increases the risk of accidents.

At a BAC of 0.05 to 0.08%, there is a four-fold increase in the risk of a motor vehicle accident.

At a BAC of 0.10 to 0.14%, there is a six- to seven-fold increase in the risk of a motor vehicle accident.

At a BAC of 0.15% and higher, there is a 25-fold increase in the risk of a motor vehicle accident.


Blood alcohol levels and the relative effect

Blood Alcohol
Up to 0.05%
Feeling of well being
Above 0.05% to 0.08%
Risk state
Judgment affected
Mood affected
Intense high or low moods
Above 0.08% to 0.15%
Dangerous state
Slow speech
Unstable balance
Blurred vision
0.20% to 0.40%
Drunken stupor
Heavy sedation
No bladder control
0.45% to 0.60%

Metabolizing alcohol

On average, a person can metabolize 7 to 10 grams of alcohol per hour. This is about the same as clearing two-thirds of the alcohol in a standard drink from the body through the liver, sweat, breath, and urine.

If you consume more alcohol in an hour than you are able to metabolize, your blood alcohol concentration will increase.

A standard drink

Alcohol concentration is usually expressed as alcohol “proof.” Proof means twice the percentage of alcohol. So, if a drink is referred to as 80 proof this means it contains 40% alcohol.

A standard drink contains approximately 13.5 grams of alcohol. See the table below for examples of standard drink equivalents.

According to the Canadian Health Network, guidelines for low-risk drinking are:

  • Drink no more than two standard drinks on any day (see table below).
  • Men should limit their weekly total of standard drinks to 14 or fewer.
  • Women should limit their weekly total of standard drinks to nine or fewer.
  • Drink slowly to avoid getting drunk. For example, wait an hour between drinks. Also, consume food and nonalcoholic beverages while drinking alcohol.

Standard drink equivalents

341 ml (12 oz)
142 ml (5 oz)
85 ml (3 oz)
43 ml (1.5 oz)
Regular-strength beer
Fortified wine
5% alcohol
12% alcohol
18% alcohol
40% alcohol


Alcohol and sleep

In small amounts (two standard drinks), alcohol taken close to bedtime can help some people relax and get to sleep easier. However, this is not a recommended sleep strategy, as alcohol can affect the quality of your sleep. In larger amounts (four or more standard drinks), alcohol will help you fall asleep or pass out quickly, but not only will it reduce the quality of your sleep, it will also lead to a more restless and light slumber toward the end of the sleep period. This may cause you to wake up feeling less refreshed.

Alcohol and performance

Drinking alcohol can lead to increased sleepiness and reduced alertness, even after the alcohol is no longer detectable. This effect is commonly known as a hangover. Alcohol intoxication significantly impairs performance, as previously mentioned

The costs associated with alcohol abuse in the workplace include:

  • Increased number of accidents causing injury
  • Increased absenteeism or lateness
  • Reduced productivity
  • Frequent stoppages
  • Lower quality work
  • Equipment damage


checkmark Knowledge Check

  • Describe three ways sleep can be affected when you have more than four standard drinks before going to bed.
  • Name four effects alcohol has on the body.
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