What is Alcohol?


Alcohol is a widely used and powerful drug which is present in alcoholic drinks. It is also known as ethanol, and is a product of fermentation of different food substances, such as grapes, barley, wheat, and rice. This drug is a central nervous system depressant that slows down the activity of the brain. Contrary to popular belief, alcohol is not a stimulant that excites brain activity.


Alcohol by Volume (ABV)


Here are some examples of alcoholic drinks and their ABV:

Alcoholic Drink

ABV (%)


3.5 – 5


11 – 15

Rice Wine


Whisky / Brandy

40 (35 – 57)

Gaoliang (sorghum wine)





  1. These are approximate figures.
  2. Alcoholic drinks that exceed 40% are considered as spirits.


The effect of alcohol on a person depends on both the type of alcoholic drink, and the amount consumed. Other factors include age, sex, overall health, and frequency of drinking.


The Liver and Alcohol


Alcohol moves rapidly through the walls of the stomach and small intestine before entering into the bloodstream. It passes through the liver in small quantities where it is broken down into carbon dioxide and water. Assuming no more alcohol is consumed, the alcohol is gradually removed from the bloodstream. However, complete removal can take a considerable time. For example, it will take the liver of a healthy adult male weighing about 80 – 90kg approximately one hour to process and remove one pint of full strength beer.


Blood Alcohol Level (BAL)


BAL is the measure of alcohol concentration in the blood. It can be stated as a decimal number or in milligrams of alcohol per 100ml of blood. BAL is an important measure, because the extent to which the nervous system and subsequent actions are slowed down or impeded is dependent on the concentration of alcohol in the bloodstream. The higher the BAL, the greater effects alcohol has on the body. If the BAL reading is over 0.45 (or 450 mg alcohol per 100 ml of blood), death is a possibility. This is because breathing can slow down so much, it may actually stop.


The BAL of an individual is dependent on a number of different factors. For example, a group of people who have consumed the same quantity of alcohol at the same time may not have the same BAL reading. Factors that affect the BAL in an individual include:


  • Their sex, weight and build.

  • Their volume of blood and bodily fluids.

  • The health of their liver.

  • The span of time over which alcohol is consumed.

  • Whether food is consumed at the same time.

  • Whether the individual is on medication.


Individuals who have lower volumes of blood and body fluids will have a higher BAL reading than those who have a greater volume of blood and water in their body. This is because alcohol dissolves more readily in water. For this reason, children or adolescents who consume alcohol are more likely to have a higher BAL, and exhibit signs of the nervous system slowing down more quickly.


Muscle tissues contain more water than fatty tissues of the same weight. Consequently women, who generally have a higher proportion of fatty tissue than men, will have a higher BAL than men, even when they consume the same quantity of alcohol within the same time frame.


Effects of Over-Consumption of Alcohol


Besides affecting health, the over-consumption of alcohol can lead to accidents and other social problems. Some of these problems are due to excessive intake in the short term, while others are due to persistent and frequent heavy consumption.


Immediate or Short-Term Effects


Once absorbed by the body, alcohol has an almost immediate effect on the nervous system. Noticeable effects include:


  • General impairment of senses

  • Delayed reactions

  • General loss of coordination

  • Depression of inhibitions (e.g. a person becomes more talkative or aggressive, which may lead to the myth that alcohol is a stimulant)


Long-Term Effects


While the long-term effects of alcohol consumption vary between individuals, any individual who regularly consumes an excess of alcohol over a period of time may suffer from some or all of the following problems:


  • Liver damage

  • Brain damage (especially loss of memory)

  • Cardiovascular disease

  • Mental problems

  • Death


Heavy drinkers may also struggle with alcoholism and suffer from negative consequences in social relationships and finances.


Alcohol-Related Problems


Problems can be avoided by not drinking or drinking in moderation. However, if an excessive amount of alcohol is consumed, some of the following problems can occur in the following scenarios or people:


Operating Machinery / Driving a Vehicle


Under the influence of alcohol, a person’s judgement is impaired, e.g. their vision blurs, they have a slower reaction time, they lose focus, co-ordination and balance. For all these reasons, they are more likely to have an accident when operating machinery or driving a vehicle. A common example is when someone drink drives: the drunk driver, his/her passenger(s), and other road users are all put at risk.


Taking Medication


If alcohol is taken together with other depressant drugs, such as tranquillisers, sleeping pills and antihistamines, the person risks further depression of the central nervous system and may show signs of alcohol poisoning.


Alcohol also interferes with the absorption and metabolism of other drugs, increasing the burden on the liver. In some cases, alcohol enhances the absorption of matter into the bloodstream so much that it can dangerously magnify the dosage of the medication absorbed by the body.


Pregnant or Nursing Mothers


If a pregnant woman has a habit of drinking, both the health of the mother and the foetus could be affected. Alcohol in the mother’s bloodstream reaches the baby via the umbilical cord, and drinking large amounts of alcohol at any point during pregnancy, especially in the first trimester, may lead to a miscarriage. If the baby survives the pregnancy, there is a chance the baby may develop Foetal Alcohol Syndrome (FAS).


Signs and symptoms of FAS include: mental retardation, short attention span, extreme anxiety and other behavioural impairments, low birth weight, small head circumference, and poor fine motor skills.


In newborn babies, the brain and other parts of the body are in the early stages of development. A nursing mother who drinks alcohol will produce breast milk containing alcohol which affects the baby’s development. In addition, alcohol consumption can inhibit the mother’s production of milk, thereby depriving the baby of natural breast milk.




Drinking alcohol carries physical and behavioural risks for adolescents. As their brains are still developing, heavy alcohol consumption can lead to the impairment of brain function. Scientists are still researching if such damage can be reversed.


In addition, as mentioned earlier, BAL increases faster in adolescents than in adults, impairing the nervous system at a faster rate. This, in turn, can affect their judgement and behaviour more quickly and to a greater intensity.


Behaviourally, young people yield more easily to peer pressure and end up drinking too much. They may then:


  • Display embarrassing conduct.

  • Become aggressive, start disputes or fights.

  • Break the law, e.g. vandalise public property, steal.

  • Become victims of violent crimes or sexual assault.

  • Become involved in unintentional injuries.

  • Suffer blackouts and not remember what happened while drunk.

  • Engage in unprotected sex, which in turn, may hurt the personal reputations of both parties, jeopardise social relationships, and result in unplanned pregnancy or contracting sexually transmitted diseases.


It is important for young people to be able to identify the circumstances in which drinking becomes too risky. To avoid these potential problems, it is best to abstain altogether. If, however, they must drink alcohol, drinking with responsible adults can help lessen the risks.


Legal Information


Police have the power to demand a breath test from any driver who:

  • Is involved in a traffic accident.

  • Has committed a moving traffic offence.

  • Is suspected of drink driving.


Additional breath, blood or urine tests are mandatory if the screening results indicate an alcohol level above the legal limit as listed below:


Proportion of alcohol in a person’s breath, blood or urine

Minimum Driving Disqualification Period


Subsequent Conviction 

(Note 1)

Tier 1
(if it exceeds the legal limit (Note 2) but is less than 35mcg / 80mg / 107mg of alcohol in 100ml of breath / blood / urine respectively)

6 months

2 years

Tier 2
(if it exceeds Tier 1 but is less than 66mcg / 150mg / 201mg of alcohol in 100ml of breath / blood / urine respectively)

1 year

3 years

Tier 3
(if it exceeds Tier 2)

2 years

5 years

Note 1:
A person is regarded as having a second/subsequent conviction in drink driving, if he has been convicted of any drink driving related offences previously, regardless of the alcohol level on the previous conviction.  The penalty for the second/subsequent conviction will be imposed according to the alcohol level in the second/subsequent conviction.

Note 2:
"Legal limit" means:
(a) 22 micrograms of alcohol in 100 millilitres of breath;
(b) 50 milligrams of alcohol in 100 millilitres of blood; or
(c) 67 milligrams of alcohol in 100 millilitres of urine.




  • Maximum fine of HK$25,000 and 3 years’ imprisonment.

  • Mandated to attend a driving improvement course.

  • Incur 10 driving offence points.

  • Assigned a driving disqualification period.


For detailed information, please refer to the following websites:


Transport Department



Department of Health