Interventions
The variety of hazardous pollutants that can occur in air or water also leads to many different interventions. Interventions pertaining to environmental hazards are often more sustainable if they address the driving forces behind the pollution at the community level rather than attempt to deal with specific exposures at the individual level. In addition, effective methods to prevent exposure to chemical hazards in the air or water may not exist at the individual level, and the only feasible individual-level intervention may be treating cases of illness.
Figure 43.1 shows five levels at which actions can be taken to prevent the health effects of environmental hazards. Some would label interventions at the driving force level as policy instruments. These include legal restrictions on the use of a toxic substance, such as banning the use of lead in gasoline, or community-level policies, such as boosting public transportation and reducing individual use of motor vehicles.
[Figure
43.1]
Interventions to reduce pressures on environmental quality include those that limit hazardous waste disposal by recycling hazardous substances at their site of use or replacing them with less hazardous materials. Interventions at the level of the state of the environment would include air quality monitoring linked to local actions to reduce pollution during especially polluted periods (for example, banning vehicle use when pollution levels reach predetermined thresholds). Interventions at the exposure level include using household water filters to reduce arsenic in drinking water as done in Bangladesh. Finally, interventions at the effect level would include actions by health services to protect or restore the health of people already showing signs of an adverse effect.
Interventions to Reduce Air Pollution
Reducing air pollution exposure is largely a technical issue. Technologies to reduce pollution at its source are plentiful, as are technologies that reduce pollution by filtering it away from the emission source (end-of-pipe solutions; see, for example, Gwilliam, Kojima, and Johnson 2004). Getting these technologies applied in practice requires government or corporate policies that guide technical decision making in the right direction. Such policies could involve outright bans (such as requiring lead-free gasoline or asbestos-free vehicle brake linings or building materials); guidance on desirable technologies (for example, providing best-practice manuals); or economic instruments that make using more polluting technologies more expensive than using less polluting technologies (an example of the polluter pays principle).
Examples of technologies to reduce air pollution include the use of lead-free gasoline, which allows the use of catalytic converters on vehicles' exhaust systems. Such technologies significantly reduce the emissions of several air pollutants from vehicles (box 43.3). For trucks, buses, and an increasing number of smaller vehicles that use diesel fuel, improving the quality of the diesel itself by lowering its sulfur content is another way to reduce air pollution at the source. More fuel-efficient vehicles, such as hybrid gas-electric vehicles, are another way forward. These vehicles can reduce gasoline consumption by about 50 percent during city driving. Policies that reduce "unnecessary" driving, or traffic demand management, can also reduce air pollution in urban areas. A system of congestion fees, in which drivers have to pay before entering central urban areas, was introduced in Singapore, Oslo, and London and has been effective in this respect.
[Box 43.3]
Power plants and industrial plants that burn fossil fuels use a variety of filtering methods to reduce particles and scrubbing methods to reduce gases, although no effective method is currently available for the greenhouse gas carbon dioxide. High chimneys dilute pollutants, but the combined input of pollutants from a number of smokestacks can still lead to an overload of pollutants. An important example is acid rain, which is caused by SO2 and NOx emissions that make water vapor in the atmosphere acidic (WHO 2000). Large combined emissions from industry and power stations in the eastern United States drift north with the winds and cause damage to Canadian ecosystems. In Europe, emissions from the industrial belt across Belgium, Germany, and Poland drift north to Sweden and have damaged many lakes there. The convergence of air pollutants from many sources and the associated health effects have also been documented in relation to the multiple fires in Indonesia's rain forest in 1997 (Brauer and Hisham-Hashim 1998); the brown cloud over large areas of Asia, which is mainly related to coal burning; and a similar brown cloud over central Europe in the summer, which is caused primarily by vehicle emissions.
Managing air pollution interventions involves monitoring air quality, which may focus on exceedances of air quality guidelines in specific hotspots or on attempts to establish a specific population's average exposure to pollution. Sophisticated modeling in combination with monitoring has made it possible to start producing detailed estimates and maps of air pollution levels in key urban areas (World Bank 2004), thus providing a powerful tool for assessing current health impacts and estimated changes in the health impacts brought about by defined air pollution interventions.
Interventions to Reduce Water Pollution
Water pollution control requires action at all levels of the hierarchical framework shown in figure 43.1. The ideal method to abate diffuse chemical pollution of waterways is to minimize or avoid the use of chemicals for industrial, agricultural, and domestic purposes. Adapting practices such as organic farming and integrated pest management could help protect waterways (Scheierling 1995). Chemical contamination of waterways from industrial emissions could be reduced by cleaner production processes (UNEP 2002). Box 43.4 describes one project aimed at effectively reducing pollution.
[Box 43.4]
Other interventions include proper treatment of hazardous waste and recycling of chemical containers and discarded products containing chemicals to reduce solid waste buildup and leaching of toxic chemicals into waterways. A variety of technical solutions are available to filter out chemical waste from industrial processes or otherwise render them harmless. Changing the pH of wastewater or adding chemicals that flocculate the toxic chemicals so that they settle in sedimentation ponds are common methods. The same principle can be used at the individual household level. One example is the use of iron chips to filter out arsenic from contaminated well water in Bangladeshi households (Kinniburgh and Smedley 2001).
