Hong Kong's Environmental Protection Department and the Environmental Protection Bureau of Guangdong Province announced the report on the monitoring results of the Pearl River Delta Regional Air Quality Monitoring Network, which covers the period between January and June 2007.

The Network measures the concentrations of four major pollutants: sulphur dioxide, nitrogen dioxide, ozone, and respirable suspended particulates. In general, air quality was better in the coastal areas than in the central and northern region of the Pearl River Delta in the first half of 2007, which could be attributed to the relatively more favorable conditions for dispersion of pollutants in the former.

The overall concentrations of most pollutants were generally higher in the winter months, such as January. They were reduced as summer approached. Apart from heavier rainfall and higher mixing layer, the relatively clean maritime air stream prevailed in the PRD region under the influence of southern monsoon also accounts for a lower level of pollution in summer time. That notwithstanding, the monthly variations in the concentrations of pollutants may change from year to year. Long-term monitoring is thus required before a general pattern can be established.

Intermittent high level of pollutants exceeding Class 2 of the National Ambient Air Quality Standards was recorded in all monitoring locations of the network in the reporting period, which was mainly triggered by meteorological conditions unfavourable to pollutant dispersion.

In the long term, the monitoring results will help the two sides to carry out scientific analysis of the air quality trends in the PRD Region. The emissions reduction measures being pursued by the two sides will make a positive impact on the regional air quality. We expect that after more Network data are available, the two sides will be able to assess the impact and effectiveness of the measures scientifically.