Tests are performed on-site not back at the station. I don't have published studies or references for you. The wiper fluid story was anecdotal, told to me when I was living in Oslo by friends. Norwegians I spoke with were understandably upset at the time limits dropped, as the law exceeded the capabilities of the equipment that enforced the law. There were chemicals that biased the sensors in the roadside equipment, leading to false positives. Innocent people were caught up just as guilty people. This was some time ago and must probably breathalyzers are much better now.
The tolerance for drunk driving there is zero. In 2010, there was a man who operated a riding mower while allegedly drunk. The incident happened on a school property. He was found guilty of drunk driving, lost his license and fined NKr 50,000 (CA$10,000).
Yes well, I assume our breathalyzers when first introduced weren't as accurate as today's. Now in Denmark they may very well do roadside screening same as we do here. However, here if you fail a roadside screening device, (The reading is over .08, current standard), then you either provide a breath sample to a breathalyzer with a trained breath tech, either on a breathalyzer in a RIDE van, or you are transported to the station, (more common that ride spot checks).
Now there is no talk of lowering the limit here to .02, so not an equal comparison. As for the person on a riding mower, that is an equal comparison. If someone here were operating a riding mower, etc on public property, here then they too would be arrested and charged with impaired operation.
After having seen, and had to deal with the devastating results of impaired driving, I have no issue with lowering the limit. I have arrested people who blew .09, yet could barely stand, as well as one fellow who blew .286 and .295, and I wasn't convinced as I transported him for the test if he would fail or pass.
Another misconception is the "natural alcohol" causing people to record a low reading. This is a myth. I have witnessed hundreds of people register a .00. The only people who will register a detectable reading, are those who have consumed the night before, or an alcoholic whose BAC is always present.