Can global health weather global climate?

Secretary-General G. O. P. Obasi of the World Meteorological Organization asks: Can Global Health Weather Global Climate?

Changes in temperature and rainfall patterns perturb ecological processes with some beneficial but largely adverse impact on health. The geographical range and seasonality of infectious disease shift especially when the source is small vectors and insects such as mosquitoes and ticks. Even a marginal fall in agricultural productivity can endanger well-being in areas of food insecurity. Warmer weather worsens urban-industrial air pollution; if it is moist as well, air concentrations of allergenic pollens and fungal spores increase. But, on the other hand, the high rate of cold weather mortality will decrease. Recent experiences with severe heat-waves, and the continuing consequences of events related to El Nino, indicate a wide spectrum of physical, microbiological and psychosocial hazards to human health.

Although humans have a great capacity to adapt to varied climates and environments, they are still vulnerable when surrounding meteorological conditions change considerably. For example, exposure to extreme temperatures may lead to heatstroke or frostbite. In most countries, people can live comfortably in the temperature range of 17 [degrees]-31 [degrees] C. However, when the temperature of the surrounding air raises the body's core temperature to above 40.6 [degrees] C, death from heatstroke can result. Scientists have also found that many more people die from causes such as heart attacks during heatwaves - albeit less severe - than during cooler periods. In addition, the human response to weather, as viewed from the point of view of "comfort", depends on temperature as well as humidity and wind. Urban populations are typically more vulnerable than their rural counterparts.

The air around us is full of particles and gases such as pollen, fungal spores and toxic emissions, which have implications for health. In addition, "acid rain" and dry toxic deposits, which contaminate farmlands, forests, water sources and fish stocks, can adversely affect huge areas, depending on meteorological conditions. Thus, the health of populations in distant areas can be affected by pollutants transported by atmospheric circulations from a small number of factories in urban areas.

This has been a major problem Europe, example, where acid rain is said to have damaged remote areas of Scandinavia. Local effects from pollution, such as smog and low-level ozone concentrations, as well as the presence in the air of certain pollens, have been linked to acute attacks of asthma and other respiratory diseases. The number of people potentially affected varies, depending on the prevailing winds and humidity that can encourage either the dispersal or concentration of the pollutants and pollens.

In other cases, the link between weather, climate and health is not direct but is nonetheless important. For example, stratospheric ozone shields the Earth's surface from incoming solar ultraviolet (UV) radiation that is harmful to all animals and plants. Depletion of the ozone layer can therefore have serious health implications. Many epidemiological studies have implicated UV-B radiation as a cause of skin cancer in fair-skinned humans and have concluded that depletion of the ozone layer could result in an increased incidence of cases. In areas of high exposure to sunshine rich in ultraviolet radiation, cataracts, as well as other damage to the eyes such as snow-blindness, are also more prevalent. Moreover, there is evidence that UV-B causes the immune system to be suppressed in humans and animals, though the wider significance of this for patterns of disease is difficult to assess.

In addition to these factors, weather-related natural disasters, such as tropical cyclones, droughts, severe floods and abnormal monsoons, also have implications for health. For instance, food supplies are destroyed, resulting in malnutrition, and water supplies deteriorate. Secondary effects include an increased risk of infectious diseases due to a breakdown in sanitation, a lack of clean fresh water, and overcrowding, as well as damage to local health care infrastructure.

Human societies over the years have been depleting a number of natural resources and degrading the environment, particularly through pollution from heavy industry, transportation and certain land-use practices. Populations have also modified their local climates by cutting down trees or building dams. The WMO/UNEP (World Meteorological Organization/United Nations Environment Programme) Intergovernmental Panel on Climate Change has concluded that "the balance of evidence suggests a discernible human influence on the global climate". Recognition has now grown that climate change to a warmer world is likely to affect the health of human populations. Increasing our understanding of the linkages between climate, weather and health will help us to forecast the impacts and take appropriate precautionary measures. Such an assessment is a complex exercise, assessing when, where and to what extent the ongoing accumulation of greenhouse gases, particularly carbon dioxide, will translate into changes in climate. It must then take account of the assessment by other scientific disciplines of how those climate changes would affect health.

Long-term changes in climate could also influence the two foundations of public health systems: sufficient food; and safe and adequate drinking water. Some assessments suggest that one third to one half of the world's vegetation types would change, and many plant and animal species would become extinct. Climate change would also have an impact on the availability of fresh water for domestic, agricultural and industrial consumption and on water quality. A rise in sea level would cause salt contamination of underground aquifers near the coasts and some river systems. A warmer world is expected to produce more severe flooding in some places and more severe droughts in others. Greater flooding can lead to increased contamination of water by human and animal waste and agricultural chemicals. Reduced water levels in other places can concentrate pollutants and pathogens in surface water. As well as affecting food supply, reduced water availability has health implications; it has been shown that, in times of water shortage, cooking takes precedence over hygiene.

(Excerpted from message on World Meteorological Day 1999)

Point of Fact: It is known that certain species of mosquito transmit malaria, the tsetse fly transmits sleeping sickness, and the black fly transmits river blindness. Because climate can play a dominant role in determining their distribution and abundance, climate change could have an effect on the geographical range of many of these insects. As a result of a warmer climate, for example, the southern United States and parts of Europe could be threatened with malaria. It is now also possible to identify habitats that favour high survival rates for tsetse flies and mosquitoes, and establish where human populations are at risk. Droughts or heavy rain after El Nino pose similar dangers; the 1997/1998 El Nino in north-eastern Kenya and southern Somalia, the associated outbreak of Rift Valley Fever, which had been effectively eradicated, killed large numbers of cattle and even spread to humans. Indeed, the aggregate effect of El Nino is so great that the global burden of natural disasters is greater in the year after the onset of El Nino, compared to the year before, with associated consequences on the health of the affected populations.

RELATED ARTICLE: A Five-Point Agenda for Action

In the first instance, National Meteorological and Hydrological Services (NMHSs) and public health authorities should, as appropriate, initiate or strengthen activities related to the provision of relevant information, such as comfort indices, pollution warnings and pollen and dust counts, and issue, among others, UV and sunburn forecasts find bioclimatic maps.

Secondly, NMHSs and public health services should strengthen their cooperation, with improved skill in weather forecasts achieved over the last decade and now available in many countries, which have saved millions of lives from tropical cyclones, floods and other severe weather events. Member countries of WMO routinely exchange such meteorological information under the World Weather Watch system.

Thirdly, NMHSs could provide seasonal forecasts to health authorities on a regular basis for use in advance planning. Considerable progress has also been made towards seasonal predictions as a result of work being carried out under the WMO World Climate Programme; new services are likely to become established during the next decade. Ability to forecast El Nino/Southern Oscillation events and other anomalous climate conditions well in advance can mitigate many of the associated adverse health impacts.

Fourthly, NMHSs could contribute further to the efficient use of scarce water resources in semi-arid and drought-prone lands, and to the assessment of water quality and quantity, contributing to improvement of agricultural production and a decrease in pollution by agricultural chemicals or other agents. WMO already supports a number of activities aimed at mitigating the adverse impacts of climate variability and change.

Fifthly, at the local or community level, climate and weather information must be expressed in terms that complement local knowledge and perceptions. WMO works to ensure that NMHSs have the capability to provide relevant guidance to decision-makers and health officials. Its Climate Information and Prediction Service project provides near-future predictions to support cooperation with them.

Information gaps need to be filled through local studies of the health impacts of short-term variations in weather and climate, making necessary more collaborative research between health scientists, meteorologists, climatologists, hydrologists and scientists from other disciplines.