The Kowloon Canton Railway Corporation (KCRC) and the environmental group Clear The Air organised a poster design competition to raise young people's awareness of air pollution.
Around 5,000 entries from 80 schools were received.
Clear The Air warned that air pollution seriously threatens public health and the economic and social well-being of all Hong Kong residents.
Many districts are failing to meet statutory health standards for air quality.
At the prize-giving ceremony, James Blake, KCRC's senior director of capital projects, said that many participants showed their understanding of the seriousness of the problem in the SAR, despite their young age.
He suggested people use public transport such as buses, trains and trams.
He said the KCRC used electrified trains, which do not pollute the air.
