Categorical Lens

Objective: Environmental Health

Air Quality

Indoor and outdoor air pollution are leading threats to human health (World Health Organization, 2006a, p. 87). Air pollution is produced by the natural or human-caused release of harmful contaminants into the atmosphere (World Health Organization, 2014). Air pollution is a global issue, affecting individuals across all countries and socioeconomic groups (World Health Organization, 2016a). The EPI uses three indicators to measure air quality: household solid fuel use, PM2.5 average exposure, and PM2.5 exceedance.

Particulate matter (PM) exposure is associated with significant adverse health effects (Kloog, Ridgway, Koutrakis, Coull, & Schwartz, 2013; World Health Organization, 2016a). These particulates can penetrate the human lung, leading to higher incidences of cardiovascular and respiratory disease (Goldberg, 2008). Recent research suggests that around five million people die prematurely every year due to air pollution, accounting for approximately one in every ten deaths annually (World Bank & Institute for Health Metrics and Evaluation, 2016). Reducing air pollution levels globally can therefore improve human health today and in future generations.

Indicators Included

  1. Household solid fuels. We measure household air pollution as the health risk posed by the incomplete combustion of solid fuels, using the number of age-standardized disability-adjusted life years (DALYs) lost per 100,000 persons due to this risk.
  2. PM2.5 exposure. As a measure of chronic exposure, we use the population-weighted average ambient concentration of PM2.5 in each country.
  3. PM2.5 exceedance. As a measure of acute exposure, we use the proportion of the population in each year that is exposed to ambient PM2.5 concentrations that exceed WHO thresholds of 10, 15, 25, and 35 micrograms per meter cubed (µg/m3) (World Health Organization, 2006a). These four proportions are averaged to produce a summary of the distribution of exposure levels in the country’s population.
Air Quality Indicators (Results | Report)
Household solid fuels (Results) DALY rate
PM2.5 exposure (Results) μg/m3
PM2.5 exceedance (Results) % population


Water and Sanitation

Access to clean water is essential for human development, the environment, and the economy. More than two billion people, however, lack access to safe drinking water, sanitation, and hygiene (World Health Organization & United Nations Children’s Fund, 2017, pp. 4–6). Poor water quality and inadequate sanitation affect all aspects of life. Inadequate access to clean water and sanitation sources hinders sustainable development efforts worldwide (World Health Organization & United Nations Children’s Fund, 2015). The chapter Water and Sanitation uses two indicators to measure the health risks associated with unsafe sanitation and drinking water sources.

Indicators Included

  1. Sanitation. We measure sanitation as the proportion of a country’s population exposed to health risks from their access to sanitation, defined by the primary toilet type used by households.
  2. Drinking water. We measure drinking water as the proportion of a country’s population exposed to health risks from their access to drinking water, defined by the primary water source used by households and the household water treatment, or the treatment that happens at the point of water collection.

Both sanitation and drinking water are measured using the number of age-standardized disability-adjusted life years (DALYs) lost per 100,000 persons. Minimizing the health risks posed from unsafe sanitation and drinking water is a vital step in evaluating a country’s ability to maintain clean water systems and minimize contact with dangerous bacteria and viruses.

Water and Sanitation Indicators (Results | Report)
Sanitation (Results) DALY rate
Drinking water (Results) DALY rate


Heavy Metals

Heavy metal exposure causes countless deaths and disabilities. The diverse range of sources and adverse health effects of heavy metals – including lead, arsenic, mercury, and cadmium – pose a complicated challenge for the world. We know that human activities are the primary driver of heavy metal production and pollution, contributing to disease and poverty on a global scale. Among heavy metals, lead is one of the most significant environmental health threats to children and pregnant women. The World Health Organization states that there is no known level of lead exposure that is considered safe, and lead poisoning in childhood is linked to cognitive impairment, violent crime in adulthood, and loss of economic productivity (Landrigan et al., 2017, p. 17).

Heavy metals have been used by humans for thousands of years. Their toxicity and tendency to accumulate in biological systems make them a significant health hazard. Some heavy metals such as copper and zinc have essential biological functions in miniscule amounts, but others – like lead, arsenic, mercury, and cadmium – can be life-threatening. Human exposure to toxic heavy metals persists globally, but the prevalence of heavy metal pollution is most notable in low- and middle-income countries (Järup, 2003, p. 167).

Indicators Included

1.     Lead exposure: lead is a major environmental threat because of its severe human health effects, and because of its global prevalence in air, water, dust and soil, and various manmade products. We measure lead exposure using the number of age-standardized disability-adjusted life years (DALYs) lost per 100,000 persons due to this risk.

Heavy Metals Indicator (Results | Report)
Lead Exposure (Results) DALY rate


Objective: Ecosystem Vitality

Biodiversity & Habitat

Biodiversity underpins all ecosystem services that sustain our environment and power our economies. Natural habitats have witnessed considerable declines in biodiversity in recent decades. Today, many species are, however, at risk of extinction. The Biodiversity & Habitat issue category seeks evaluate a country's performance in habitat conservation and species protection. 

Each nation's Biodiversity & Habitat score reflects a composite of six underlying indicators. Our selected indicators are highlighted in the Convention on Biological Diversity's "Aichi Targets", a set of internationally agreed upon goals for conservation and ecosystem management (Secretariat of the Convention on Biological Diversity, 2014). The indicators in Biodiversity & Habitat are: marine protected area, terrestrial biome protection - national weights, terrestrial biome protection - global weights, species protection index, protected area representativeness, and species habitat index.

Indicators Included

  1. Marine protected area: The percentage of marine protected areas (MPAs) within a country's exclusive economic zone.
  2. Terrestrial biome protection - national weights: The percentage of biomes in protected areas, weighted by national composition of biomes.
  3. Terrestrial biome protection - global weights: The percentage of biomes in protected areas, weighted by global composition of biomes.
  4. Species protection index: The average area of species' distributions in a country with protected areas.
  5. Protected area representativeness index: The extent to which terrestrial protected areas are ecologically representative.
  6. Species habitat index: The proportion of habitat within a country remaining, relative to a baseline set in the year 2001. 
Biodiversity and Habitat Indicators (Results | Report)
Marine protected area (Results) % of EEZ
Terrestrial biome protection - national weights (Results) % of biomes (capped)
Terrestrial biome protection - global weights (Results) % of biomes (capped)
Species protection index (Results) Unitless
Protected area representativeness index (Results) Unitless
Species habitat index (Results) Unitless

We draw particular attention to the protected area representativeness and species habitat indices, as these indicators represent new metrics within the 2018 EPI. These new indicators reflect international efforts to develop a common and more complete system for monitoring changes in biodiversity.


Approximately 1.6 billion people depend on forests for their livelihoods (United Nations, 2015, p. 1). Forests are not only crucial for economic development and human well-being, but global climate regulation and other vital ecosystem services (World Wide Fund for Nature, 2017b). Finally, forests provide important habitat for more than 80% of terrestrial animals, plants, and insects (United Nations, 2015, p. 1). Understanding where changes in forest cover occur is thus essential for sustainable development (Food and Agriculture Organization of the United Nations, 2016a). The Forests issue category uses one indicator to measure the threats to forests worldwide: tree cover loss. We include tree cover loss as an indicator for forest health due to its significant implications for ecosystem health, habitat preservation, climate change mitigation, and other environmental services.

Indicators Included

  1. Tree cover loss: We measure the total area of tree loss in areas with greater than 30% tree canopy cover divided by the forest cover in the year 2000. We apply a 5-year rolling average to better capture trends in forest management strategies.


Forest Indicators (Results | Report)

Tree cover loss (Results) %, 5-year



Global fisheries are a critical resource for food security, as well as employment and income. Fish also function as an integral part of marine ecosystems. In virtually all developing countries, fisheries provide vital sources of protein and micronutrients (Golden et al., 2016, p. 317). As of 2014, more than 56 million people worked in capture fishing and aquaculture (Food and Agriculture Organization, 2016, p. 5). Despite their global importance and growing attention to over-fishing, fish stocks continue to decline across most of the world. Unsustainable fishing emerges as the main cause of this decline, with 31% of stocks considered overfished (World Wide Fund for Nature, 2016, p. 38). Experts predict this decline will continue into the future as no fish stocks are expected to be underexploited within twenty years (Daniel Pauly & Zeller, 2017, p. 178). Dramatic changes in fisheries management are needed to protect global marine systems, and the societies dependent upon these resources.

The EPI utilizes two indicators to evaluate country performance in fisheries management: fish stock status and regional marine trophic index (RMTI).

Indicators Included

  1. Fish stock status: This indicator is based on an assessment of the percentage of fish stocks caught within a country’s Exclusive Economic Zone (EEZ) that are overexploited or collapsed.
  2. RMTI: This indicator is a measure of the mean trophic level of fish caught by a country, which represents the overall health of the ecosystem.
Fisheries Indicators (Results | Report)
Fish stock status (Results) % of catch
RMTI (Results) Unitless


Climate and Energy

Climate change lies at the heart of some of the most pervasive and intractable environmental problems. Global energy and transport systems release heat-trapping gasses into the atmosphere that warm the surface of the planet and degrade public health. Growing demand for food, commodities, and new development further shape spatial structures and landscapes in ways that alter the earth’s ability to reflect or absorb heat. These impacts, and others, are producing a strong cascade of effects that imperil existing social and economic structures and threaten the sustainability of our planet. Curtailing the effects of anthropogenic climate change will require immediate, concerted action by all countries at all scales.

Indicators Included

The Climate & Energy issue category uses five indicators to track a country’s progress in reducing three critical greenhouse gases and one climate pollutant. In adding non-CO2 indicators to the 2018 EPI, we have broadened the gauge of national climate change performance. We leverage new emissions inventories to construct a series of metrics intended to yield a more comprehensive assessment of a country’s overall performance.

We measure each country’s Climate & Energy score across the following five indicators:

  1. Carbon Dioxide – Total. This CO2 metric tracks trends on carbon intensity from the entire economy, in terms of metric tonnes of CO2 emissions per unit of GDP.
  2. Carbon Dioxide – Power Sector. This CO2 metric tracks trends on carbon intensity from the power sector, in terms of metric tonnes of CO2 emissions per unit of kWh of electricity and heat.
  3. Methane. Tracks trends in national emissions intensities of methane gas, reported in metric tonnes of CO2-equivalent per unit of GDP.
  4. Nitrous Oxide. Tracks trends in national emissions intensities of nitrous oxide emissions, reported in metric tonnes of CO2-equivalent per unit of GDP.
  5. Black Carbon. Tracks trends in national emissions intensities of black carbon emissions, reported in Gigagrams (Gg) of black carbon per unit of GDP.
Climate and Energy Indicators (Results | Report)
Carbon dioxide - total (Results) kt CO2eq/B$
Carbon dioxide - power sector (Results) g CO2/kWh
Methane (Results) kt CO2eq/B$
Nitrous oxide (Results) kt CO2eq/B$
Black carbon (Results) kt CO2eq/B$


Air Pollution

Air pollutants negatively affect ecosystem integrity and function. Both sulfur oxides (SOX) and nitrogen oxides (NOX) can cause acidification, which can degrade soil and water quality. NOX deposition can further cause eutrophication, the excessive enrichment of nutrients. The addition of reactive nitrogen to a system can further trigger a cascade of ecological effects that reduce plant biodiversity. As a result, these pollutants are very harmful to both natural vegetation and agricultural crops. Acidification and eutrophication driven by atmospheric pollutants can be difficult or impossible to reverse, persisting long after emissions reduction policies are implemented. It is therefore imperative, especially in industrializing nations, to reduce emissions of long-range air pollutants to protect the health of global ecosystems.

Indicators Included

The two indicators used for air pollution are NOX and SO2 emission intensity. The 2018 Environmental Performance Index (EPI) uses data from the Emissions Database for Global Atmospheric Research (EDGAR) v4.3.1 global anthropogenic emissions inventory of gaseous and particulate air pollutants.

Air Pollution Indicators (Results | Report)
Sulfur oxide (Results) Mt/constant 2011 international $
Nitrogen oxide (Results) Mt/constant 2011 international $


Water Resources

Effective wastewater management is essential to human and ecosystem health. Untreated wastewater contaminates rivers, lakes, and oceans. It spreads diseases that kill millions of people each year. Ecosystem impacts from wastewater range from eutrophication to increased water temperature, depending on the wastewater source. Wastewater pollution threatens ecosystem vitality and clean water resources in all countries, but the need for wastewater management is especially pressing in countries facing water scarcity. Growing populations also threatens the ability of some countries to ensure clean fresh water resources. Connecting people to adequate wastewater collection and treatment systems mitigates these damages by preventing pollution and making treated water available for re-use.

Indicator included

1.     Wastewater treatment: We measure wastewater treatment as the percentage of wastewater that undergoes at least primary treatment in each country, normalized by the proportion of the population connected to a municipal wastewater collection system.

Countries can minimize the negative environmental impacts of sewage by treating wastewater. Water treatment can remove pathogenic microorganisms and other harmful pollutants, minimizing health risks to humans and ecosystems. Maximizing wastewater treatment is an effective way to assess the cleanliness of each country’s water resources. Our wastewater treatment indicator captures only water treatment by centralized municipal utilities, as global data from independent water treatment such as private septic systems are lacking. 

Water Resources Indicator (Results | Report)
Wastewater treatment (Results) %



Agriculture is crucial to sustaining life, but agricultural productivity has often come at the expense of agricultural inputs, such as land, water, and minerals (Alexandratos & Bruinsma, 2012). Sustainable farming and ranching thus depend on better and more efficient use of resources to break this link. Fertilizers rich in nitrogen support plant growth and are thus vital to the agricultural sector. (Zhang et al., 2015, p. 51). Nitrogen pollution, however, has the potential to cause widespread damage if managed inadequately (Bodirsky et al., 2014). The EPI uses one indicator to track nitrogen management as a measure of environmental performance.

Indicator Included

  1. Sustainable nitrogen management index (SNMI). As a gauge of efficiency, the SNMI indicator uses nitrogen use efficiency (NUE) and crop yield to measure the environmental performance of agricultural production (Zhang & Davidson, 2016).
Agriculture Indicators (Results | Report)
Sustainable nitrogen management index (Results) unitless