Are you over 0.05?

In Australia, drivers must have a blood alcohol

concentration (BAC) of less than 0.05% (w/v), i.e. 0.05g of alcohol per 100ml

of blood. If your BAC exceeds 0.05%, you will be convicted of ‘driving under

the influence’.

Alcohol

readily distributes into all of the water spaces in the body, which is why

consuming alcohol quickly has such a dramatic effect, and there is a rapid equilibrium

between body water spaces and the bloodstream. So the BAC can be calculated based

on:  

• the amount of alcohol ingested (in grams)

• an estimate of the individual’s water volume (in mL

  or litres)

In Australia, by law, the alcohol content must be

stated on all alcoholic drinks. The % alcohol is actually % ethanol (v/v), i.e.

mL/100mL. Typical values are:

• Spirits  40%

• Beer     4-5%

  (craft beers are higher)

• Wine   

  11-15% (but quite variable)

Water content of the human

body is also estimated as a %, but % (w/w), i.e. g/100g

• Healthy young ♂   60%
• Healthy young ♀   55%

Car

or taxi??

A group of friends are having a night out. They have

decided to have a few quick drinks early, then to switch to soft drinks for the

later part of the evening.

• Ben (70kg) has two 375mL craft beers (6%),
• Jim (75kg) has three pots (285mL) of mid-strength beer (3.5%),
• Alan (85kg) has two shots (44mL) of Jim Beam (40%) and
• Meg (60kg) has two 120mL glasses of wine (12%).

They then receive a call telling them that Ben’s

father has been rushed to hospital. Is anyone legally fit to drive?