Less than half of Philadelphians are wearing masks properly when outside, suggests a recent study released by the Philadelphia Department of Public Health.

The study, conducted by academic and private-sector researchers, observed 4,600 people in 30 outdoor public spaces including intersections, neighborhood parks, and playgrounds over the last three weeks of August in all 10 districts of the city. They found that 43% of people wore masks correctly when outside, 40% wore no masks, and 17% wore masks incorrectly.

According to the U.S. Centers for Disease Control and Prevention, proper mask protocol to limit the spread of COVID-19 includes wearing the mask over your nose and mouth, securing it under your chin and making sure it fits snugly against the sides of your face. The CDC recommends everyone over age 2, except those who have trouble breathing, wear a mask in public.

The researchers also observed that 51% of women wore their mask properly, while only 37% of men did. Among age groups, 60% of seniors wore their masks properly, compared with 21% of teens. Philadelphians identified as Asian had the highest percentage of proper mask use at 63%, compared with 47% of whites, and 35% of both Black and Latino people.

Researchers plan to collect more data regarding mask use in September and October, before releasing a final report in November.