Scientists have detected drugs including caffeine and methamphetamine in the air of downtown Auckland.
A University of Auckland study looked for four substances at Customs Street, near the bottom of Queen Street.
It found nicotine in the highest average concentrations, followed by caffeine, methamphetamine, and THC from people smoking cannabis.
The concentration of meth was higher than in overseas cities that have conducted similar tests such as Barcelona, while caffeine and THC were found at lower concentrations than other cities.
The study's authors say it shows air testing could be useful for measuring drug use.
University of Auckland School of Chemical Sciences research fellow Dr Joel Rindelaub told Morning Report while it may sound scary, no one was getting high just by walking around downtown Auckland.
"The concentrations we measured were at very very low levels, something that wouldn't even affect you, but they were there and we did have the technology to detect them."
Levels were at less than a trillionth of a gram per breath you take, he said.
"So, that's going to equal out maybe 8000 years worth of breath in order to get an active dose."
Rindelaub said this could be a complementary technique to add to wastewater monitoring done in major cities.
"There is potential for air quality to monitor a lot of different things, not just chemicals as well."
Knowing the chemicals in the air we breathe was really important, he said.