Box 1.2 Indicators of environmental threats to health

WRI has developed new indicators to assess the extent of risks to health that people face from environmental threats in different countries of the world. Creating such indicators is fraught with difficulty, because national-level data are often lacking, necessitating the use of surrogate measures. For instance, most countries do not report information on how many of their population are exposed to potentially harmful levels of indoor air pollution from the use of smoky fuels. A rough surrogate can be constructed using the amount of biomass fuel used per household. Thus, these indicators are not precise measures of actual risk but rather rough gauges based on data availability and quality.

As described in the text, WRI developed separate indicators for developing and developed countries. For the developing country indicator, WRI selected several measures that represent potential environmental threats to health and then aggregated them, in a procedure described below. Because environmental threats to health are many and varied in developing countries, this indicator attempts to measure risks from three sources: air, water, and food. The air component for the developing country indicator includes three measures representing potential exposure to poor quality air: exposure to polluted indoor air, exposure to polluted ambient air, and exposure to air polluted with lead from gasoline.

The water component for the developing country indicator includes measures of percent of population without access to safe water, without adequate sanitation, and potential exposure to malaria (as a surrogate for a number of insect-borne diseases). The nutrition component includes three measures representing potential exposure to poor nutrition: percent of children under 5 years of age who are underweight, total number of available calories per person, and percent of population at risk of either vitamin A or iodine deficiency (whichever micronutrient deficiency was higher).

The three measures within each component of the developing country indicator were ranked from lowest (lowest relative risk) to highest (highest relative risk). If the number of countries with data available differed among the three measures, the ranks were standardized, or spread, to match the maximum number of ranks for any of the three measures. The three ranks from the three measures were then averaged (each country must have at least two measures to be included in the calculation), and the final average rank was ranked again from lowest to highest risk.

The next level of aggregation was to combine the ranks of the three components. Here again, when the number of countries with available data differ, the ranks were standardized to match the maximum number or ranks for any of the three measures. The ranks of the three components were then averaged (each country must have at least two measures to be included in the final ranking), and the final average rank was ranked again. The final result was a list of developing countries ranked according to potential exposure to the three components and associated measures. The final rank was separated into high, medium, and low categories of potential, relative risk by dividing the countries into three equal groups.

For developed countries, WRI developed two indicators rather than a single aggregated index. One indicator suggests potential exposure to polluted ambient air; the other suggests potential exposure to air polluted with lead used in gasoline. The lead indicator is shown in Potential Exposure to Air Polluted with Lead from Gasoline: Developed Countries; the ambient air pollution indicator is included in the Environmental Risks to Human Health: New Indicators but is not mapped because of insufficient data. In both of these indicators, countries were ranked from lowest to highest exposures. To determine the final rank, the countries were divided into three equal groups, reflecting high, medium, and low potential risk.

In these preliminary indicators, the final rankings for each country should be considered suggestive, to be used as a basis for exploring environmental health threats in greater detail. WRI used the best available data to construct the indicator, but still, the data were often incomplete or unreliable. Dividing nations into thirds to designate the three risk categories is, admittedly, arbitrary. There may be very little difference between countries at the cut-off points between high and medium risk or medium and low risk. The broad categories, however, suggest differences in relative risks, and the indicator maps serve as preliminary tools for identifying countries with different potential for exposure to environmental health threats.