Public health

Drought is a prolonged dry period in the natural climate cycle. It is a slow-onset phenomenon cause by a deficit in rainfall combined with other predisposing factors, and affects millions of people a year. In 2013 alone, nearly 8 million people were impacted by major droughts worldwide. Droughts result in acute and chronic health effects, which include malnutrition due to decreased food availability; increased risk of communicable diseases due to malnutrition, inadequate or unsafe drinking water and a lack of proper sanitation; increased risk of airborne and dust related diseases; changes in disease carrying vector behavior; psycho-social stress and mental disorders; disruption of local health services due to decreased availability of water supplies; and an overall increase of population displacement.

The health and well-being of all peoples ultimately relies on the conditions of natural environments, be it due to a dependence on food and water security, fuel availability, or vector regulation, pests and pathogen control. A changing climate may alter the way organisms interact and where they live. For instance, the geographic and seasonal distribution of a species is dependent on climatic variables, such as temperature and precipitation. Changing temperatures can therefore expand insect vector ranges, changing the geographic limits (both in latitude and altitude) of infectious diseases like malaria and dengue. Land-use changes (e.g. deforestation, dams, and irrigation projects) also expose populations to significant health risks. With over 1 billion cases and 1 million deaths from vector-borne diseases alone, ecological change presents a major environmental health risk.

Storms, cyclones and floods can cause widespread devastation, and thereby present a major environmental health risk. Between 1994 and 2013, floods alone were responsible for the majority (43%) of natural disasters; affecting nearly 2.5 billion people worldwide. Among a number of adverse socioeconomic impacts, floods have devastating consequences on human health causing thousands to die every year. They can impact human health directly by causing deaths, injuries and mental traumas, or indirectly by creating favorable conditions for the spread of diseases, and damaging critical public health infrastructure.

Extreme temperatures such as heat waves and cold spells can have significant effects on human health and are associated with increased morbidity and mortality. Temperature extremes heighten health risks, especially in vulnerable population such as children and the elderly, chronically ill, socially isolated persons, and people working outdoors or in exposed environments. Heat waves are a growing public health threat, with every Centigrade above a threshold level increasing deaths by 2-5%. During heat waves, a large proportion of the excess deaths are due to cardiovascular, cerebrovascular and respiratory disease, however excess cases of heatstroke, heat stress, and other heat-related illnesses can increase rapidly during periods of extreme temperatures. (Read more: Heatwaves and Health: Guidance on Warning-System Development)

While the effects of heat waves on health are usually acute and felt only for a few days in, cold spells can have effects that last for weeks. In temperate countries, winter mortality rates are 10-25% higher than in summer, partly associated with increases in seasonal respiratory infections or influenza outbreaks, as well as cardiovascular and cerebrovascular events. Adaptability to cold temperatures plays an important role in preventing winter deaths. Death rates are seen to increase more in populations that usually experience warmer winters; or where people have inadequate heating and clothing. The impacts of cold waves can be particularly severe in tropical climates as recent events in North Africa, South Asia and South East Asia have shown. 

Air pollution is characterized by a contamination of the indoor or outdoor (ambient) environment by any agent that modifies natural characteristics of the atmosphere. Air pollution causes several million deaths each year and is a leading environmental health risk affecting everyone. Nearly 4.3 million premature deaths per year are attributable to indoor air pollution and roughly 3.7 million premature deaths are thought to be caused by outdoor air pollution (2012 WHO estimates). Adverse health impacts result from particles in the air such as dirt, pollen, dust, soot, and smoke, or hazardous materials including chemicals and radiological materials. These pollutants are released by both human and natural sources, such as through the burning of fossil fuels for electricity and transport, industrial processes, agricultural practices, or forest fires, volcanic eruptions, and wind-blown dust.

Excessive exposure of ultraviolet (UV) radiation from the sun damages human health. Health consequences range from premature ageing of the skin to skin cancer. UV radiation can also damage the cornea, lens and retina of the human eye, and can contribute to the formation of cataracts and other forms of ocular damage. The number of malignant melanoma cases has doubled every 7 to 8 years over the last four decades, with a marked increase of skin cancers in fair-skinned populations. Populations vulnerable to UV Radiation include those living in regions with damaged Ozone layers (Australia); persons working outdoors; and children, as evidence suggests that early exposure to sun increases the likelihood of skin cancer development later in life.

Monitoring and modeling of radiation dispersion

Water is essential to life on Earth, and human health directly depends on access to clean water. Availability of quality fresh water is not only essential for populations’ drinking supplies, but also for agricultural practices as well as sanitation and hygiene purposes. Over 2.6 billion people today live without access to improved sanitation facilities, and nearly 900 million people do not receive their drinking-water from improved water sources. The quality of water can be compromised by the presence of toxic chemicals, radiological hazards, and infectious agents that give rise to waterborne diseases such as diarrhea, cholera, dysentery and typhoid. Diarrhea as a result of contaminated drinking water is estimated to cause half a million deaths each year. The WHO estimates that by 2025, half of the world’s population will be living in water-stressed areas, partially due to climate change. 

• The Global Analysis and Assessment of Sanitation and Drinking-Water (GLAAS) is a UN-Water initiative implemented by the World Health Organization (WHO), in collaboration with partners, including WMO. Its objective is to provide policy makers at all levels with a reliable, easily accessible, comprehensive and global analysis of the evidence to make informed decisions in sanitation and drinking-water. 
• Other relevant issues: Wastewater