“Climate change is one of the most urgent health threats to address globally .” This phrase pronounced by the director general of the World Health Organization (WHO), Tedros Adhanom Ghebreyesus, a few days before the 2019 United Nations Climate Action Summit started, may seem alarmist. However, each word makes sense if we analyze the figures that experts shuffle: between 2030 and 2050, it is estimated that 250,000 more people will die each year due to climate change , according to UN data. Of these, 38,000 will be elderly people who will not survive the heat, another 48,000 individuals will die from diarrhea and 60,000 from malaria. And about 95,000 children will die as a result of malnutrition coupled with the climate crisis.
“There are epidemiological studies that estimate that, at a European level, for each degree that the ambient temperature increases, the mortality of the population can increase between 1% and 4%,” warns Ricardo Gómez Huelgas, president of the Spanish Society of Internal Medicine (SEMI). And you don’t have to go far to see if the forecasts are fulfilled: it is already happening.
This was the case with the heat wave that hit Europe in the summer of 2003 , with temperatures exceeding 45 ° C in some parts of Andalusia or even 37 ° C in the United Kingdom, and which killed about 70,000 people in the Old Continent. Spain, during that summer, had 8% more deaths , which occurred in individuals 65 years of age and older, as concluded by an investigation published in the journal Gaceta Sanitaria .
Today, around 30% of the world’s population is exposed to climatic conditions that exceed the threshold for heat mortality for at least twenty days a year. And, for the future, the forecasts are not encouraging at all: it is expected that in 2100, if we do not reduce greenhouse gas (GHG) emissions, the percentage will close to 50%. Ignoring the threat of very high temperatures could cause them to end up affecting three-quarters of the world’s population, according to a recent study published in Nature Climate Change .
If we review the Fifth Assessment Report of the IPCC (the UN Intergovernmental Panel on Climate Change), the most recent to date, since the middle of the 20th century, warm days and nights have increased and, with them, both waves like heat stroke. These consist of “an uncontrolled increase in body temperature that produces multi-organ failure,” explains Gómez Huelgas, who is already seeing more and more cases of this type, especially in the population at risk , such as the elderly and patients with chronic diseases. Less frequently, blows also affect younger people who perform work or physical activities under high-temperature conditions, such as construction, agricultural work, and sports training.
Rising temperatures and changes in ecosystems associated with the climatic emergency due to droughts, deforestation or rising sea levels will also lead to an increase in the number of diseases transmitted by insects, such as malaria and dengue. . “All diseases involving reservoirs and vectors have an enormous dispersal capacity and are, therefore, the most affected by climate change and global change, as we have seen recently in the case of urogenital schistosomiasis ( a parasitic infection) in Europe or those transmitted by mosquitoes ”, highlights María Dolores Bargues, president of the Spanish Society of Tropical Medicine and International Health (SEMTSI).
Vectors are living organisms that can transmit infectious diseases between people and also from animals to humans. As Bargues lists, mosquitoes are the best known vectors of diseases, although there would also be ticks, flies, sand flies –they transmit leishmaniasis–, fleas, triatomines –Chagas disease– and some freshwater snails . In this way, among the ailments spread by these insects and mollusks that will be affected by climate change are some well-known ones, such as malaria, dengue, the aforementioned leishmaniasis and yellow fever; and others not so much, such as the aforementioned schistosomiasis, human African trypanosomiasis or sleeping sickness, Chagas disease, Japanese encephalitis and onchocerciasis or river blindness.
Research published in The Lancet compared the world dengue scenario in 1990 with an estimate for 2085. If in 1990 almost 30% of the total population – 1.5 billion individuals – resided in regions where the estimated risk of dengue transmission was higher at 50%, in 2085, with the projections made on climate change, the population at risk would practically double: it would be between 50% and 60% and would affect around 5000 or 6000 million people. If we were not facing a climate change scenario, the proportion would drop to 35%.
“Many vector-borne diseases are sensitive to climate, but dengue is the most important viral infection . Malaria will also increase in areas that are currently too cold for spread, ”says Simon Hales, professor in the Department of Public Health at the University of Otago, New Zealand and lead author of the study.
Malaria is of particular concern in our country. As the president of SEMTSI recalls, Spain obtained the disease eradication certificate in 1964. However, to date, vector mosquitoes persist in the territory and have caused some cases of autochthonous transmission in recent years. This situation, added to the effect of climate change, means that there are active mosquitoes not only in summer, but even until the months of October or November, which increases the risk of transmission.
“The main consequence is that the propagation periods, not only of malaria, but of many other diseases transmitted by mosquitoes, are extended, and it can be the case of contagion throughout the year or that some diseases appear in countries that previously did not they suffered them ”, the expert warns.
We could say that environmental pollution and climate change are two sides of the same coin. On the one hand, the increase in carbon dioxide emissions – CO 2 is a type of GHG – causes global warming and this, in turn, leads to climate change – which consists of global variations in the Earth’s climate -. On the other hand, GHGs and particulate matter (PM) are responsible for air pollution.
Worldwide, the UN estimates that pollution is responsible for the premature death of seven million people each year , including 600,000 children. If we look at Europe, annual deaths due to this pollution are close to 800,000 and reduce life expectancy by more than two years, according to a study published in the European Heart Journal . Most of these deaths were caused by cardiovascular diseases.
“We expect a significant increase in cardiorespiratory diseases; basically, myocardial infarctions, heart failure and angina pectoris ” , summarizes José Luis Palma, vice president of the Spanish Heart Foundation. Although, in principle, anyone is susceptible to suffering them with an increase in environmental pollution, there are more vulnerable groups, such as the youngest, the elderly, immunosuppressed patients, hypertensive patients, diabetics and people with advanced tumor processes.
Luis Palma warns that they are already seeing more hospitalizations for heart failure or angina those days when pollution levels in large cities exceed the established limits . “The impact on cardiovascular health is tremendous. It has already been established that climate change and environmental pollution have a very negative impact ”, he assures.
Both phenomena form the perfect couple so that other types of disorders also increase: specifically, allergies . This is how several studies describe it, such as one published in the journal Environmental Science & Technology , which concluded that the Anthropocene – the current era in which we find ourselves, which is characterized by the obvious influence of the human being – causes chemical modifications of allergens – substances that cause allergic reactions–, increases oxidative stress –a type of cellular deterioration– and unbalances the immune system towards allergic reactions.
Those responsible for these effects would be carbon dioxide, ozone, nitrogen oxides and atmospheric particles related to combustion or traffic. “Increased temperatures and CO 2 concentration in the air can cause longer pollen seasons and alter pollen production and the bioavailability of allergens,” says Kathrin Reinmuth-Selzle, researcher in the Institute’s Multiphase Chemistry department. Max Planck from Chemistry (Germany) and lead author of the study.
Also, according to Reinmuth-Selzle, extreme events can lead to asthma flare -ups that arise in the wake of storms. Also climate change and air pollution would cause people to be more sensitive to allergic responses and even modify the allergens themselves, which increases their potential to generate a reaction in the body, as occurs with birch pollen.
As for the diseases of this type that will be more common, the researcher lists allergic rhinitis, allergy to grass and birch pollen, atopic asthma, eczema (atopic dermatitis) and immune reactions caused by food .
Another consequence of the climate crisis is extreme weather events of greater intensity, such as droughts, tropical cyclones and hurricanes . In these cases, the disasters they generate are accompanied by serious health problems for the thousands of victims.
“Apart from the physical damage and depression or anxiety suffered by victims after a disaster, the lack of access to drinking water increases the risk of diarrhea and the shortage of food favors malnutrition “, stresses Anna Fernández Ortiz, coordinator of the group of I work in Planetary Health and head of the Young Family Physicians Section of the Spanish Society of Family and Community Medicine (semFYC).
As we have seen, between 2030 and 2050, about 50,000 people will die each year from diarrhea. And what favors this intestinal alteration? The lack of drinking water, something that is common in situations of drought or extreme phenomena in which clean stream sources are contaminated. Something similar happens with farmland: too little or too much water will reduce crops and the diversity of food grown in certain regions, leading to hunger and malnutrition.
Climate change will worsen the living conditions of farmers, fishermen and those who live off forests , populations that are already vulnerable and with food instability, according to the Food and Agriculture Organization of the United Nations (FAO). “As in other situations, climate change increases health inequities between rich and poor, and diseases affect the latter more,” laments Fernández Ortiz.
In addition to causing a lack of water, global warming will also have a negative impact on its quality. “Higher temperatures could trigger the proliferation of microorganisms such as legionella”, indicates Cristina Rius, member of the Spanish Society of Epidemiology and head of the Epidemiology Service of the Barcelona Public Health Agency. Aside from physical illness, mental health will also suffer from the climate crisis . On the one hand, devastating tragedies, such as hurricanes and tornadoes, will leave thousands of people homeless, causing, for example, anxiety attacks and depression; in fact, half of the survivors of Hurricane Katrina in 2005 developed post-traumatic stress disorder even without having suffered direct physical losses, a study revealed.
But, in addition, there will be other more silent victims, much less obvious, who will suffer the consequences of the changes on the planet. For example, extreme heat exposure leads to exhaustion in vulnerable people and other mental health risks, including suicide .
According to research published in Nature Climate Change , suicide rates in the United States and Mexico rose 0.7% and 2.1%, respectively, when average monthly temperatures increased by one degree Celsius. If their estimates are met and they continue to rise at that rate, between now and 2050 between 9,000 and 40,000 more people could kill themselves in these two countries, which is the equivalent of the number of suicides that usually accompany an economic recession.
Public health experts, epidemiologists, cardiologists, psychiatrists and primary care physicians urge authorities to comply with international commitments, such as the Paris Agreement, to try to curb climate change. But are these professionals prepared for the disease spike to come?
Experts from the European Center for Disease Prevention and Control (ECDC) admit that, for infectious diseases transmitted by food, water and vectors in Europe, current surveillance practices would need “some adjustments”. However, they highlight the good functioning of the database and the network of specialists that they share with the European Food Safety Authority (EFSA) on the distribution of vectors and infectious microorganisms in Europe and the Mediterranean basin.
In Spain, in 2004 the Center for the Coordination of Health Alerts and Emergencies was created , which directs the management of information and supports the response to alert situations or health emergencies that pose a threat to the well-being of the population.
“Numerous organizations are collaborating to guarantee the training of physicians in health and environmental issues,” highlights Fernández Ortiz, who cites the WHO, the UN, the Planetary Health Alliance and other entities that offer postgraduate courses for health professionals on health global and talks to involve the population. They seem to be prepared for the worst. And we?
