Families should boil rather than roast their Sunday lunch to avoid indoor pollution levels worse than the most toxic cities on Earth, scientists have said.

New research is showing that preparing the traditional meal with the windows shut gives readings up to 13 times worse than in central London on a congested day.

The world’s largest gathering of scientists heard that pollutants from roasting include PM2.5 particulates, which are particularly harmful because they are small enough to embed deep into the lungs and, in some cases, even enter the bloodstream.

Experiments during Thanksgiving in the US found that cooking a full roast turkey dinner pushed readings to peak levels of 200 micrograms per cubic meter (m/cm).

The World Health Organization safety limit for PM2.5 particulates is 10 m/cm, although central London averages 15.2.

The research team said that roasting vegetables contributes badly to indoor pollution levels badly because cooks often aim for a charring or blackening effect. They singled out Brussels sprouts as particularly harmful because of how quickly the vegetables blacken when roasted.

While boiling both meat and vegetables would still emit PM2.5, doing so is healthier for the internal atmosphere of a house than roasting, the scientists said.