【Talking about famous medical experts】
Since this summer, the temperature in many parts of the country has broken through historical extremes. According to the monitoring and assessment of the National Climate Center, the comprehensive intensity of this year's regional high temperature events has reached the strongest level since complete meteorological observation records began in 1961, with the characteristics of long duration, wide range, high intensity and strong extreme. Health events such as heat stroke and heat stroke caused by hot weather are frequently searched. In the context of frequent extreme weather, we can't help but ask, who is the "behind the scenes" of all this?
The sixth assessment report of the United Nations Intergovernmental Panel on Climate Change (IPCC) pointed out that the earth's climate system is undergoing significant changes with warming as the main feature, and the rate of global warming in the past 50 years is unprecedented. At the same time, the frequency and intensity of extreme weather events have increased significantly, leading to serious consequences such as melting glaciers and rising sea levels. It has been recognized that the increasing emissions of greenhouse gases such as CO2 caused by human activities are an important cause of global warming. In the context of climate change, there are complex links between extreme weather, environmental pollution, and biodiversity loss. Coupled with the spread of COVID-19 around the world, human health is facing enormous challenges.
Humans themselves are very sensitive to climate change. Heat waves can induce respiratory, circulatory and other systemic diseases, and even lead to premature death; while floods can cause water pollution and food shortages, which in turn lead to increased health risks such as infectious diseases and nutritional deficiencies. At the same time, extreme weather events will also bring huge psychological and psychological damage to the survivors. In the future, climate change is likely to surpass environmental pollution as the greatest threat to human health. Under the background that extreme weather events caused by global warming are becoming more frequent, more intense and wider in scope, how to fully understand the relationship between climate change and health and effectively deal with the health risks brought about by climate change is an important issue for human society in 21 The severe challenges facing the century.
1. Temperature health effects in the context of climate change
The most important and direct impact of climate change on human health is the health effects caused by exposure to extreme temperatures.
China is a sensitive area for global climate change, and the warming rate is higher than the global average level over the same period. During the period from 1951 to 2021, the annual average temperature in my country will increase by about 0.26 °C every 10 years; and there are obvious seasonal and regional differences in the warming rate. The temperature rises faster than in summer, and the Qinghai-Tibet region has the largest warming rate, followed by North China, Northeast China and Northwest China.
In addition to long-term small warming, climate change has also triggered more extreme and more intense human health effects of sustained high temperature weather events - heat waves.
Entering the new century, the frequency and intensity of heat waves in my country have increased significantly, and high-incidence areas have continued to spread in East and Central China.
Heat waves not only lead to heat-related diseases such as heat stroke and heat stroke, but also increase the risk of morbidity and mortality of cardiovascular, respiratory, urinary, nervous system and other diseases.
When exposed to high temperature, the thermoregulatory center can increase sweat secretion and promote body heat dissipation through the co-regulation of nerves and body fluids, but at the same time, it also causes the loss of a large amount of water and salt in the body, which increases blood viscosity and reduces visceral blood perfusion. , thereby increasing the cardiovascular burden.
The elderly, children, pregnant women, outdoor workers, people with underlying diseases and other groups are the most affected groups.
For example, a study in Guangzhou found that for every 1°C rise in temperature, the incidence of work-related accidents increased by 1.4%.
In terms of regional differences, the health risks in temperate continental climate regions and temperate monsoon climate regions are much greater than those in subtropical monsoon climate regions, and the number of heatwave-related deaths in East and Central China is also higher than in other regions.
In the context of global warming, although winter temperatures will increase, extreme cold waves will also occur.
The main reason is that climate change has caused rapid warming in the polar regions, weakening of the polar vortex, and the splitting of cold air in the polar vortex to the south, resulting in widespread cold weather in Eurasia and North America.
In a low temperature environment, the metabolism of human tissues is enhanced, and the demand for oxygen increases, which in turn causes vasoconstriction and significantly increases the risk of death from cardiovascular and respiratory diseases.
A study based on surveillance data from 272 cities across the country found that low temperatures lead to a higher risk of death among populations than high temperatures.
Climate change will also lead to increased fluctuations in temperature variability, such as intraday, daytime, seasonal and interannual temperature anomalies.
Temperature changes can affect the pathophysiological response of airway epithelial cells at the tissue level, which in turn affects the health of the body.
Studies have found that every time the temperature variability in my country exceeds 1°C in winter, the risk of emergency hospitalization for total respiratory disease, pneumonia and chronic obstructive pulmonary disease increases by 20%, 15%, and 41%, respectively.
In addition, climate change will also lead to compound extreme temperature events, mainly including continuous high temperature day and night and compound temperature and humidity events.
Studies have shown that high temperature events in my country have gradually changed from daytime extreme high temperature to nighttime and day and night continuous extreme high temperature events. Compared with pure daytime high temperature, day and night continuous high temperature events have a greater impact on human health.
Combined exposure to extreme temperatures and ambient humidity also poses greater risks to human health.
In a high-temperature and high-humidity environment, due to the high water vapor content in the air or even saturation, the human body's ability to perspire is reduced, and it is difficult for the sweat to evaporate after sweating, which makes the human body unable to dissipate heat normally, and the body is more prone to discomfort and heat stroke.
On the contrary, in a low-humidity environment, dry air is more likely to irritate the eyes, nose and throat of the human body, which can cause acute attacks of respiratory diseases.
2. The increasing health impacts of extreme weather events
Climate change has led to a significant increase in the frequency and intensity of extreme weather events such as floods, droughts, and typhoons.
In recent years, extreme weather events have occurred frequently and strongly in my country. Floods and typhoons in the eastern and southern regions are intense and extreme in intensity, and the frequency of meteorological droughts in the western and northern regions has increased, resulting in large-scale severe sand and dust weather.
Extreme weather events can seriously threaten the living environment and health of human beings, not only causing direct casualties, but also increasing the risk of infectious diseases, non-communicable diseases and mental and psychological diseases.
In addition, my country has a large population base, high population density, complex climate types, unbalanced socio-economic development, and diverse health problems for vulnerable groups.
Extremely heavy precipitation and the flood disasters caused by it can affect or even destroy infrastructure, change the geographical distribution of vector organisms, cause casualties and outbreaks of infectious diseases.
A study based on 254 cities across the country showed that precipitation in temperate, warm temperate and subtropical zones in my country significantly increased the risk of hemorrhagic fever with renal syndrome, a rat-borne disease.
A number of studies in southern China have also shown that the risk of acute hemorrhagic conjunctivitis, influenza, tuberculosis, meningitis, dengue fever and other infectious diseases increases significantly after floods.
Drought can lead to water shortage and pollution, resulting in long-term accumulation of allergens, dust, and pollutants in the environment that cannot be washed away by rainwater, thereby increasing the risk of morbidity and mortality from insect-borne, fecal-oral and other infectious diseases, as well as respiratory diseases.
The prevalence and severity of wildfires are also increasing due to climate change, frequent droughts and altered precipitation patterns.
Wildfires can affect respiratory disease, particularly exacerbation of asthma and chronic obstructive pulmonary disease, through pathways such as thermal injury and smoke exposure.
In addition, drought and high temperature are also special weather backgrounds formed by sandstorms, which are one of the most frequent extreme weather events in Northwest China.
Dust from sandstorms can damage the human skin and respiratory system, leading to diseases such as bronchitis, and also increases the risk of accidental injury due to poor visibility during sandstorms.
In recent years, the frequency of strong typhoons and super typhoons in my country has increased significantly.
Typhoons and the secondary disasters such as torrential rain and storm surge caused by typhoons are intense and destructive, which can lead to direct casualties and increase the risk of infectious diseases.
Research from Guangdong shows that typhoons lead to increased mortality among residents, and women, infants and the elderly are more vulnerable.
Studies in the southeastern coastal areas of my country show that typhoons significantly increase the risk of bacillary dysentery, paratyphoid fever, dengue fever, and acute hemorrhagic conjunctivitis.
Research in the Pearl River Delta region shows that the risk of dengue fever in the affected areas increases significantly after the typhoon.
In addition, typhoons and their secondary disasters will also directly or indirectly affect the mental and psychological health of the affected people. For example, super typhoon Sangmei caused negative emotions and post-traumatic stress disorder in Cangnan, Zhejiang.
3. The combined effect of climate change, air pollution and allergens
Changes in meteorological conditions and the occurrence of extreme weather events will affect the concentration and distribution of air pollutants and airborne allergens in the atmosphere.
Air pollution and greenhouse gases have the same root. The burning of fossil fuels will not only produce a large amount of air pollutants, but the greenhouse gases will also aggravate global warming. Climate change can not only affect the concentration of air pollutants in the atmosphere, but also promote photochemical The reaction produces secondary pollutants.
On the other hand, global warming will prolong the pollen season of plants, increase the pollen concentration in the air, and enhance the allergenicity of pollen, thereby increasing the burden of allergic diseases.
Climate change will have a combined effect with air pollution and airborne allergens, affecting the occurrence and prevalence of climate-sensitive diseases, and causing complex risks to human health.
Extreme events such as forest fires and sandstorms will produce more particulate matter, nitrogen compounds, and sulfides. Meteorological factors increase the air pollution in the breathing environment of people by affecting the production, transportation and deposition processes of air pollutants, as well as the generation of secondary pollutants. substance concentration.
High temperatures may accelerate ozone production by increasing the concentration of major ozone precursors and promoting photochemical reactions, and lightning in warm and humid climates also increases nitrogen oxide production.
These additional increases in air pollution are a serious threat to population health.
There is a synergistic effect of high temperature and air pollution on the health of the population. When the two work together on the human body, they will have a greater health impact and increase the risk of premature death, cardiovascular and respiratory diseases, and adverse maternal outcomes.
In addition, the loss of body fluids when exposed to high temperature will aggravate the inflammation of the bronchial mucosa caused by air pollutants, reduce the threshold of bronchoconstriction and make it more likely to induce asthma attacks.
Climate change will also directly or indirectly affect the occurrence of allergic diseases through allergens such as pollen, mold, and spores.
Climate warming will lead to an increase in the number of frost-free days, which will lead to an earlier pollen season and a longer pollination time of allergenic plants. The increase in greenhouse gases will also stimulate plant growth and reproduction, making it produce more pollen, increase the expression of allergenic proteins, and enhance the Allergenicity of pollen.
In addition, extreme weather, such as high winds and thunderstorms, can lead to higher concentrations of allergens in the air and their wider spread.
For example, the hydration and electrolysis reactions caused by thunderstorm events can cause pollen and spores in the air to release more allergens, while drought and windy weather can cause aerosols carrying allergens to spread farther, these smaller diameters and The fine particles carrying allergenic substances can penetrate deep into the lower respiratory tract of the human body and induce allergic bronchial inflammation.
Studies have shown that on the day of severe thunderstorms, the concentration of vegetation pollen in the air is as high as 400 grains per cubic meter, and the number of asthma-related hospitalizations increased by nearly 10 times.
4. Strategies and actions to address the health risks of climate change
The Chinese government has always attached great importance to the response to climate change, and has taken active actions, including formulating contingency plans to deal with different disasters such as floods and typhoons, carrying out assessments of the health impacts of extreme weather and surveys on climate change adaptability, etc. Some cities have established early warnings for climate-sensitive diseases, such as the dengue fever surveillance and early warning system in Guangdong Province.
In the future, my country urgently needs to establish a climate-resilient public health system, which can effectively respond to the shocks and pressures related to climate change and continuously improve the health of the population.
For example, the recently released "National Climate Change Adaptation Strategy 2035" proposed to encourage the assessment of climate change health risks and adaptation capacity in the fields of health and public health, strengthen the monitoring, early warning and prevention and control of climate-sensitive diseases, and enhance the climate resilience of the medical and health system. And comprehensively promote the healthy adaptation of climate change.
Scientific research is a prerequisite for fully understanding the health risks of climate change. my country is still in its infancy, and more in-depth research is urgently needed.
Relevant scientific research units should carry out scientific research on climate change health risks in a planned way, assess current and future health risks of climate change, and identify climate-sensitive diseases and vulnerable groups.
The health department needs to strengthen close cooperation with the meteorological department to achieve real-time sharing of relevant data resources, and establish an online database system of healthy weather to carry out monitoring and forecasting of infectious diseases, chronic diseases, and mental and psychological diseases.
In addition, government departments and scientific research institutions should also carry out popular science education in various forms to improve the public's awareness of the health impact of climate change, provide health guidelines for high temperature weather, and scientific knowledge on how to properly respond to and self-rescue in extreme weather.
Establishing an early warning system for climate change and health risks is an important measure to deal with the health impacts of climate change.
my country needs to continuously improve its meteorological scientific and technological capabilities, strengthen linkages and data sharing among various departments, further develop and improve climate change health risk monitoring and prediction models and technologies on various time scales, and establish an early warning system for climate-sensitive diseases, including forecasting local weather and identifying Extreme weather, determination of specific risk trigger thresholds, early warning signal release and dissemination, risk communication and action recommendations, etc., form public health emergency response and risk management decision-making methods for climate change and extreme events.
For example, take the early warning system of high temperature, heat wave and health risk as a pilot action, release information based on meteorological or climate forecast to the public, remind decision makers and relevant health departments to formulate emergency plans and treatment methods, and call on the public to take countermeasures, thereby reducing Mortality and morbidity of heat-related diseases.
Given the high importance the public and society place on health, it is imperative for governments to integrate health into the climate decision-making process, fully consider the potential impacts and co-benefits of climate policies and action strategies on population health, and formulate more cost-effective and socially acceptable technical routes .
From a personal point of view, citizens should strengthen environmental awareness and form a moderate saving, green and low-carbon, civilized and healthy lifestyle and consumption pattern.
In short, in the face of the severe situation of intensified global warming, we should deepen our correct understanding of the concepts of a community with a shared future for mankind, the construction of ecological civilization and sustainable development, and promote the development of society in the direction of sustainable utilization of the earth's resources and harmonious coexistence between man and nature .
(Author: Huang Cunrui, Professor of the Vanke School of Public Health and Health, Tsinghua University, Chief Scientist of the National Key R&D Program)