Discussing blood alcohol levels in English

Solution 1:

I prosecuted people for DUI in the state of Illinois, so I may be able to offer a perspective of the legal jargon, the police vernacular, and the language of the lay person. To me, the following road sign speaks volumes:

The sign is an official government sign to warn the population. It does not mention units at all. David Garner is right that extremely few people in the US could name the unit involved. I know from working with police officers and from attending training for prosecutors who prosecute DUIs that most police officers and lawyers cannot describe the unit of measurement.

As further evidence of the lack of understanding of the unit of measurement, some people will make statements such as, "Susan had a point oh six and Jack had a point twelve, so he was twice as drunk as she was." Of course, BAC is not a magically precise measure of the degree of impairment, but because most people do not understand what is being measured, they cannot make proper comparisons between different BAC values.

To explicitly address your two examples, in my opinion, a non-professional writer but native speaker of American English would write the following:

According to the police report, his blood alcohol content was .16.
The legal limit for driving a car is .08.

I believe they would say ".16" as "point one six" and ".08" as "point oh eight."

Solution 2:

A quick Web-search confirms that the current UK limit is "80 milligrams of alcohol per 100 millilitres of blood", but I don't think we use units 'in everyday English'. We might say, "The police measured his blood-alcohol and it was 160 - twice the legal limit", but if you asked the average Brit, I don't think they'd be able to name the unit.