The natural assimilative capacity of the air cannot be directly enhanced, nor can centralised pollution treatment plant be provided such as in the case of marine waters. Pollution abatement, as a means of enhancing assimilative capacity therefore has to be applied at the source of the pollutant emission. Major static sources of pollutants such as power stations and industry can make a contribution to this process, for example through the installation of pollution abatement technologies such as filters, scrubbers and desulphurisation plant. Far more difficult to control are emissions from mobile sources in particular road traffic, although there are measures which can be taken including fiscal (eg fuel tax, road pricing), technical (eg fuel quality, emissions abatement) and regulatory instruments to effect abatement.

In practice a range of measures, together with demand management approaches, will be necessary to limit emissions from these sources. Declining air quality in Hong Kong is an issue of serious concern and long term maintenance of assimilative capacity will require approaches other than traditional end-of-pipe abatement. These approaches need to consider pollution problems at source such as choice of fuel use and efficiency of industrial and commercial processes (energy use is discussed in Section 3.6). Similarly, the development of alternative fuels for vehicles (and even alternative vehicles) rather than focusing on exhaust gas mitigation technologies, will be important. Transport is a key contributor to air pollution and technological measures may need to be accompanied by policy and commercial, administrative and regulatory changes to influence the demand for environmentally friendly forms of travel. These might include transport planning measures such as road pricing as well as combined transport and land use planning approaches to improve both the quality and accessibility of public transport such that more environmentally acceptable means of mobility such as mass transit systems are fully exploited.

Enhancement of assimilative capacity in Hong Kong is also important from the perspective of health since studies have indicated that worsening air quality is can be correlated with greater incidence of respiratory diseases. A study undertaken by the Chinese University of Hong Kong (CUHK 1997) and subsequent work by the University of Hong Kong (HKU 1998, 1999b) found air pollution to have an effect on circulatory and respiratory diseases. The CUHK study found significant positive associations between daily hospital admissions and deaths due to respiratory and circulatory diseases and the measured levels of O3 and NO2. The 1998 HKU study confirmed the relationships albeit with slightly lowered correlations though the follow up study in 1999 noted that the short-term effects of air pollutants on health are strong, with NO2, RSP and O3 all having effects on health outcomes individually. The 1999 study concluded that the short-term effects of air pollutants on health are likely to be the cause of increased admissions for cardio-respiratory disease in Hong Kong. The effects observed were also greater than those summarised from comparable studies undertaken in Europe using the Air Pollution on Health: A European Approach (APHEA).