How is Air Pollution measured?
In Hong Kong, the government uses an index system to monitor the air quality. The Air Pollution Index (API) converts air pollution data from several types of pollutants into a value ranging from 0 to 500. The data for the measurement and calculation of the API comes from 14 air pollution monitoring stations (11 general stations, 3 roadside stations) throughout Hong Kong.
The principal drawback of using an index system is that, being an averaging system, it can mask an extremely high level of a certain pollutant if others happen to be low, at any given time, even though all the pollutants measured can cause significant harm to human health. It is far more accurate and safer to measure pollutants separately, as they are measured by the Hedley Environmental Index (HEI), and the World Health Organisation (WHO).
The HEI website gives an explanation of why it does not follow the HK Government’s API system:
“Hong Kong’s Air Pollution Index (API) is based on the government’s own standards (Air Quality Objectives) for air quality management, with arbitrary lines above or below which air quality is considered good or poor. These standards are based on outdated evidence of the effects of air pollution. Reluctance to change them may be influenced by political considerations of what government officials believe to be realistically achievable targets in the short term. Hong Kong’s Air Quality Objectives were established over 20 years ago do not reflect current evidence of the impact of air pollution on health.”
