Fine dust concentration reaches alarming levels when cooking food on stoves using oil without proper ventilation, the Environment Ministry said.

The ministry said it measured the concentration level of PM2.5 -- the fine particulate matter smaller than 2.5 micrometers in diameter -- that build up while cooking on a stove at 32 sample houses and calculated the average.

The tests showed that after some 10 minutes of pan-frying mackerels the level of PM2.5 surged to 2,290㎍㎥. This is a 76-fold denser than the average level of fine dust in the air and 25-fold more than the standard level of 90㎍㎥ that prompts fine dust warning. Other dishes tested included samgyeopsal (pan-fried pork belly), fried egg and fried rice.

Other contaminants such as formaldehyde and nitrogen dioxide were also created.

The ministry said it was crucial to cook with the vent turned on or with windows open during and after cooking with oily ingredients.