Greenhouse gases … climate change…and human health

The so called “greenhouse gases” are those that absorb and emit infrared radiation, trapping heat and making the planet warmer. Human activity is responsible for almost all of the increase in greenhouse gases in the atmosphere over the last 150 years. The largest source of greenhouse gas emissions from human activities is from burning fossil fuels for electricity, heat and transportation.

The major non-gas contributor to Earth’s greenhouse effect, clouds, also absorb and emit infrared radiation and thus have an effect on greenhouse gas radiative properties.

Climate change, as defined by the European Journal of Internal Medicine, corresponds to significant variations of regional or global climates over long periods, includes major changes in average and peak temperature, humidity, atmospheric pressure, precipitations, wind patterns and water salinity, as well as a decrease in the size of mountain and polar glaciers. The supply of safe water is also endangered by climate change.

Although the average climate conditions have been relatively stable for millennia, the last 50 years have witnessed an acceleration of changes, so that the average global temperature has increased by 0.7°C and is expected to further increase between 1.8 and 4.0°C by the year 2100.

The main cause of the ongoing warming of the Earth must be sought in the increasing emissions into the lower atmosphere of carbon dioxide (CO2) and other greenhouse gases resulting from human activities.

Greenhouse gases absorb some of the radiation emitted from the Earth, trapping more heat in the lower atmosphere and thereby increasing temperatures. Climate experts strongly believe that climate change will lead to increasingly frequent and severe heat waves and extreme weather events, as well as to a rise in sea levels. Accordingly, it is becoming clearer and clearer that climate change over relatively short time periods pose serious threats to human wellbeing and health.

Climate effects on health
Effects of global climate change on human health may be direct or indirect. Investigators have been mainly focused on the direct effects of extreme weather events, such as heat waves, droughts, cyclones and tropical storms, for which empirical data is readily available and correlations are easily demonstrable.

Unfortunately, there is more … the secondary effects related to climate change such as the worsening of ambient air quality and the impact on infectious disease diffusion are also extremely relevant for the quality of human health.

It can easily be understood that, in the earlier stages, the climate changes may bring some health benefits. For instance, if winter in mid-latitude temperate countries becomes milder, morbidity and mortality from respiratory and cardiovascular disease should decrease and common conditions such as arthritis and related chronic pain may also improve.

However, the negative effects of global climate change far outweigh the potentially positive ones, because warmer temperatures will lead to more frequent, intense and longer heat waves, which are well-documented to be associated with adverse effects on health.

Climate models project up to a 50% increase in the frequency and intensity of the hottest days in Europe and North America in the second half of the 21st century.

Extreme heat markedly increases the number of related illnesses and deaths, children and elderly patients with chronic respiratory or cardiovascular disease being more susceptible. For example, the 2003 European heat wave caused a higher mortality peak as more than 22,000 people died, involving particularly the older citizens of Northern European countries not adapted to heat. Each year in the USA, approximately 400 people die from heat-related illness, like heat exhaustion and heat stroke.

Heat and drought greatly contribute to the occurrence of wildfire, which has dramatically increased in frequency in Mediterranean areas. Smoke emissions can travel hundreds of kilometres downwind of fire areas, exposing many people to a noxious mixture of harmful compounds.

According to a recent estimate, as many as 339,000 deaths may be attributed annually worldwide to landscape fire smoke.

Food production
Desertification and droughts related to climate changes are major public health issues, especially regarding the ability of low-income countries to maintain sufficient food production as well as adequate supplies of safe water. The World Health Organisation ranked malnutrition as the largest global health problem associated with climate change. In a recent analysis, malnutrition was found to be responsible for a large proportion of global deaths due to pneumonia in children under the age of five. It has been estimated that sub-Saharan Africa and South Asia, whose food supplies are already limited, will have the largest reductions in food supply as a result of climate changes.

Ambient air pollution
Warmer temperatures increase the concentrations of air pollutants, mainly ozone and particulate matter that are of particular relevance for cardiopulmonary health. High ozone exposure owing to heat waves was associated with a reduction in lung function and exacerbation of respiratory symptoms contributing to more premature deaths in people with heart and lung disease. Short-term elevations in ozone have been associated with increases in all-cause mortality.

The negative impact on health of fine and ultrafine particles, which penetrate deeper into the lungs and may pass into the bloodstream, are the most dangerous, inducing a premature mortality about 15 times higher than that due to ozone. It is evident that high temperatures make it all much worse.

The warming climate is also likely to worsen the global burden of allergic diseases, mainly through the anticipation in time of the onset of warmer seasons and thus of the concentration of aeroallergens. Studies in the eastern Mediterranean region have emphasised that the earlier and more lasting presence of aeroallergens exacerbates the prevalence of allergic rhinitis, asthma and skin diseases.

Infectious diseases
Changes in temperature and rainfall patterns, particularly extreme events, might enhance the spread of infectious diseases. Many infectious agents and their vector are sensitive to climatic conditions, like salmonella and cholera bacteria that proliferate more rapidly at higher temperatures.

Climate warming altered the length of seasons leading to an increased incidence of malaria, the occurrence of more spread outbreaks of dengue fever and the recent diffusion of the West Nile virus.

Humans, think properly!
All that was stated above is based on a large amount of data that indicates unequivocally that the global environment is undergoing profound changes, mostly induced by the excess of greenhouse emissions from human activities, primarily due to the increasing and widespread use of fossil fuels.

Climate changes can influence the emergence of infectious diseases, affect food yields and nutrition, the supply of safe water and thereby increase the risks of climate-related disasters. It is also actually evident that climate changes are not only an environmental and economic problem but also play a significant role in population health.

A recent projection done by the World Health Organisation to evaluate the number of additional deaths foreseen in the near future, provided there is no intervention on climate changes, gave a gloomy picture for the year 2030: 38,000 additional deaths in the elderly due to heat exposure, 48,000 in children due to diarrheal disease, 60,000 due to malaria and 95,000 due to undernutrition in children.

The degree of inevitable future changes in climate, with dramatic consequences for humanity, will be mainly determined by worldwide approaches meant to decrease the use of fossil fuels. The alternative technology already exists making it possible to implement, at a global level, effective strategies to reduce the impact that global warming has on human life.

Climate change is the most important threat to humanity this century.

We can only hope humanity will open its eyes and see the real threat caused by humans’ self-destroying, irrational, voluntary, arrogant blindness.

Best health wishes,
Maria Alice

Dr Maria Alice
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Dr Maria Alice is a consultant in General and Family Medicine. General Manager/Medical Director – Luzdoc International Medical Service. Medical Director – Grupo Hospital Particular do Algarve/ Hospital S. Gonçalo de Lagos