Regulations and policy measures related to the reduction of ambient particulate matter

The aim of this paper was to review the existing regulations and policy measures related to the reduction of airborne particulate matter, which is perhaps the most complex airborne pollutant to understand and manage. The paper discusses the existing health guidelines for particulate matter concentration, as well as the directions in setting national standards. In relation to particle mass concentration, there are no threshold levels, nor is there a linear exposure-health response relationship. At this point in time, epidemiological studies are yet to provide any quantification of exposure-response relationships in relation to particle number concentration (ultrafine particles), and the only existing number concentration standards are for clean rooms. Motor vehicle emission standards are generally provided in terms of total particle mass emissions, however, for light-duty diesel vehicles, a particle number limit has recently been introduced, whereas standards relating to industrial emissions commonly regulate total emissions of particulate matter. There are many other sources of airborne particulate matter, including aviation, shipping, biomass combustion or waste incineration, which are not directly regulated in terms of particle emissions.