The Hedley Environmental Index monitors and publishes in real-time the economic costs of Hong Kong's air pollution in terms of public health impacts and their monetary value. The public health impacts include premature deaths, hospital bed-days and doctor visits: see http://hedleyindex.sph.hku.hk/
The Hong Kong Observatory monitors visibility in Hong Kong: see http://www.hko.gov.hk/contente.htm
Investigation questions
1. Compare the measurements of air pollutant levels and visbility. Is there a correlation between visbility and pollutant levels?
2. Is there one particular type of pollutant that affects visibility more than the others?