The effects of climate change on human health are increasingly well studied and quantified. [1] [2] Rising temperatures and changes in weather patterns are increasing the severity of heat waves, extreme weather and other causes of illness, injury or death. Heat waves and extreme weather events have a big impact on health both directly and indirectly. When people are exposed to higher temperatures for longer time periods they might experience heat illness and heat-related death. [3]
In addition to direct impacts, climate change and extreme weather events cause changes in the biosphere. Certain diseases that are carried by vectors or spread by climate-sensitive pathogens may become more common in some regions. Examples include mosquito-borne diseases such as dengue fever, and waterborne diseases such as diarrhoeal disease. [3] [4] Climate change will impact where infectious diseases are able to spread in the future. Many infectious diseases will spread to new geographic areas where people have not previously been exposed to them. [5] [6]
Changes in climate can cause decreasing yields for some crops and regions, resulting in higher food prices, food insecurity, and undernutrition. Climate change can also reduce water security. These factors together can lead to increasing poverty, human migration, violent conflict, and mental health issues. [7] [8] [3]
Climate change affects human health at all ages, from infancy through adolescence, adulthood and old age. [7] [3] Factors such as age, gender and socioeconomic status influence to what extent these effects become wide-spread risks to human health. [8] : 1867 Extreme weather creates climate hazards for whole families, particularly those headed by women. It can also reduce the earning capacity and economic stability of people. Populations over 65 years of age are particularly vulnerable to heat and other health effects of climate change. [7] Health risks are unevenly distributed across the world. [8] Disadvantaged people are particularly vulnerable to climate change. [3] : 15
The health effects of climate change are increasingly a matter of concern for the international public health policy community. In 2009, a publication in the general medical journal The Lancet stated that "Climate change is the biggest global health threat of the 21st century". [9] The World Health Organization reiterated this in 2015. [10]
Research shows that health professionals around the world agree that climate change is real, is caused by humans, and is causing increased health problems in their communities. Studies also show that taking action to address climate change improves public health. Health professionals can act by informing people about health harms and ways to address them, by lobbying leaders to take action, and by taking steps to decarbonize their own homes and workplaces. [11] Studies have found that communications on climate change that present it as a health concern rather than just an environmental matter are more likely to engage the public. [12] [13]
The effects of climate change on human health can be grouped into direct and indirect effects. [8] : 1867 Both types of effects interact with social dynamics. The combination of effects and social dynamics determines the eventual health outcomes. Mechanisms and social dynamics are explained further below:
These health risks vary across the world and between different groups of people. For example, differences in health service provision or economic development will result in different health risks for people in different regions, with less developed countries facing greater health risks. In many places, the combination of lower socioeconomic status and cultural gender roles result in increased health risks to women and girls as a result of climate change, compared to those faced by men and boys (although the converse may apply in other instances). [8]
The following health effects that are related to climate change have been identified: cardiovascular diseases, respiratory diseases, infectious diseases, undernutrition, mental illness, allergies, injuries and poisoning. [8] : Figure 2
Health and health care provision can also be impacted by the collapse of health systems and damage to infrastructure due to climate-induced events such as flooding. Therefore, building health systems that are climate resilient is a priority. [14] [3] : 15
Impact of higher global temperatures will have ramifications for the following aspects: vulnerability to extremes of heat, exposure of vulnerable populations to heatwaves, heat and physical activity, change in labor capacity, heat and sentiment (mental health), heat-related mortality. [3]
The global average and combined land and ocean surface temperature show a warming of 1.09 °C (range: 0.95 to 1.20 °C) from 1850–1900 to 2011–2020, based on multiple independently produced datasets. [15] The trend is faster since the 1970s than in any other 50-year period over at least the last 2000 years. [15]
A 2023 study estimated that climate change since 1960–1990 has put over 600 million people (9% of the global population) outside the "temperature niche" - the average temperature range at which humans flourish. [16]
A 2020 study projects that regions inhabited by a third of the human population could become as hot as the hottest parts of the Sahara within 50 years without a change in patterns of population growth and without migration, unless greenhouse gas emissions are reduced. The projected annual average temperature of above 29 °C for these regions would be outside the "human temperature niche" – a suggested range for climate biologically suitable for humans based on historical data of mean annual temperatures (MAT) – and the most affected regions have little adaptive capacity as of 2020. [17] [18] The UK Met Office came to similar conclusions, reporting that the "numbers of people in regions across the world affected by extreme heat stress – a potentially fatal combination of heat and humidity – could increase" "from 68 million today to around one billion" if the world's temperature rise reaches 2°C, [19] albeit it is unclear if that limit or the 1.5 °C goal of the Paris Agreement is achieved.
Vulnerable people with regard to heat illnesses include people with low incomes, minority groups, women (in particular pregnant women), children, older adults (over 65 years old), people with chronic diseases, disabilities and co-morbidities. [3] : 13 Other people at risk include those in urban environments (due to the urban heat island effect), outdoor workers and people who take certain prescription drugs. [3] Exposure to extreme heat poses an acute health hazard for many of the people deemed as vulnerable. [3] [21]
Climate change increases the frequency and severity of heatwaves and thus heat stress for people. Human responses to heat stress can include heat stroke and hyperthermia. Extreme heat is also linked to low quality sleep, acute kidney injury and complications with pregnancy. Furthermore, it may cause the deterioration of pre-existing cardiovascular and respiratory disease. [2] : 1624 Adverse pregnancy outcomes due to high ambient temperatures include for example low birth weight and pre-term birth. [2] : 1051 Heat waves have also resulted in epidemics of chronic kidney disease (CKD). [22] [23] Prolonged heat exposure, physical exertion, and dehydration are sufficient factors for the development of CKD. [22] [23]
The human body requires evaporative cooling to prevent overheating, even with a low activity level. With excessive ambient heat and humidity during heatwaves, adequate evaporative cooling might be compromised.
A wet-bulb temperature that is too high means that human bodies would no longer be able to adequately cool the skin. [24] [25] A wet bulb temperature of 35 °C is regarded as the limit for humans (called the "physiological threshold for human adaptability" to heat and humidity). [26] : 1498 As of 2020, only two weather stations had recorded 35 °C wet-bulb temperatures, and only very briefly, but the frequency and duration of these events is expected to rise with ongoing climate change. [27] [28] [29] Global warming above 1.5 degrees risks making parts of the tropics uninhabitable because the threshold for the wet bulb temperature may be passed. [24]
Further study found that even a wet bulb temperature of 31 degrees is dangerous, even for young and healthy people. This threshold is not uniform for all and depend on many factors including environmental factors, activity and age. If the global temperature will rise by 3 degrees (the most likely scenario if things will not change), temperatures will exceed this limit at large areas in Pakistan, India, China, Sub Saharan Africa, United States, Australia, South America. [30]
People with cognitive health issues (e.g. depression, dementia, Parkinson's disease) are more at risk when faced with high temperatures and ought to be extra careful [31] as cognitive performance has been shown to be differentially affected by heat. [32] People with diabetes and those who are overweight, have sleep deprivation, or have cardiovascular/cerebrovascular conditions should avoid too much heat exposure. [31] [33]
The risk of dying from chronic lung disease during a heat wave has been estimated at 1.8-8.2% higher compared to average summer temperatures. [34] An 8% increase in hospitalization rate for people with Chronic Obstructive Pulmunary Disease has been estimated for every 1 °C increase in temperatures above 29 °C. [21]
The effects of heatwaves tend to be more pronounced in urban areas because they are typically warmer than surrounding rural areas due to the urban heat island effect. [35] [36] : 2926 This is caused from the way many cities are built. For example, they often have extensive areas of asphalt, reduced greenery along with many large heat-retaining buildings that physically block cooling breezes and ventilation. [21] Lack of water features are another cause. [36] : 2926
Extreme heat exposure in cities with a wet bulb globe temperature above 30 °C tripled between 1983 and 2016. [35] It increased by about 50% when the population growth in these cities is not taken into account. [35]
Cities are often on the front-line of climate change due to their densely concentrated populations, the urban heat island effect, their frequent proximity to coasts and waterways, and reliance on ageing physical infrastructure networks. [37]
Health experts warn that "exposure to extreme heat increases the risk of death from cardiovascular, cerebrovascular, and respiratory conditions and all-cause mortality. Heat-related deaths in people older than 65 years reached a record high of an estimated 345 000 deaths in 2019". [3] : 9 More than 70,000 Europeans died as a result of the 2003 European heat wave. [38] Also more than 2,000 people died in Karachi, Pakistan in June 2015 due to a severe heat wave with temperatures as high as 49 °C (120 °F). [39] [40]
Increasing access to indoor cooling (air conditioning) will help prevent heat-related mortality but current air conditioning technology is generally unsustainable as it contributes to greenhouse gas emissions, air pollution, peak electricity demand, and urban heat islands. [3] : 17
Mortality due to heat waves could be reduced if buildings were better designed to modify the internal climate, or if the occupants were better educated about the issues, so they can take action on time. [41] [42] Heatwave early warning and response systems are important elements of heat action plans.
Heat exposure can affect people's ability to work. [3] : 8 The annual Countdown Report by The Lancet investigated change in labour capacity as an indicator. It found that during 2021, high temperature reduced global potential labour hours by 470 billion - a 37% increase compared to the average annual loss that occurred during the 1990s. Occupational heat exposure especially affects laborers in the agricultural sector of developing countries. In those countries, the vast majority of these labour hour losses (87%) were in the agricultural sector. [2] : 1625
Working in extreme heat can lead to labor force productivity decreases as well as participation because employees' health may be weaker due to heat related health problems, such as dehydration, fatigue, dizziness, and confusion. [43] [1] : 1073–1074
With regards to sporting activities, it has been observed that "hot weather reduces the likelihood of engaging in exercise". [2] : 1625 Furthermore, participating in sports during excessive heat can lead to injury or even death. [1] : 1073–1074 It is also well established that regular physical activity is beneficial for human health, including mental health. [2] : 1625 Therefore, an increase in hot days due to climate change could indirectly affect health due to people exercising less.
Climate change is increasing the periodicity and intensity of some extreme weather events. [44] Confidence in the attribution of extreme weather to anthropogenic climate change is highest in changes in frequency or magnitude of extreme heat and cold events with some confidence in increases in heavy precipitation and increases in the intensity of droughts. [45]
Extreme weather events, such as floods, hurricanes, droughts and wildfires can result in injuries, death and the spread of infectious diseases. For example, local epidemics can occur due to loss of infrastructure, such as hospitals and sanitation services, but also because of changes in local ecology and environment.
Examples include:
Global climate change has increased the occurrence of some infectious diseases. [58] Infectious diseases whose transmission is impacted by climate change include, for example, vector-borne diseases like dengue fever, malaria, tick-borne diseases, leishmaniasis, zika fever, chikungunya and Ebola. One mechanism contributing to increased disease transmission is that climate change is altering the geographic range and seasonality of the insects (or disease vectors) that can carry the diseases. Scientists stated a clear observation in 2022: "the occurrence of climate-related food-borne and waterborne diseases has increased (very high confidence)." [59] : 11
Infectious diseases that are sensitive to climate can be grouped into: vector-borne diseases (transmitted via mosquitos, ticks etc.), waterborne diseases (transmitted via viruses or bacteria through water), and food-borne diseases. [60] : 1107 Climate change is affecting the distribution of these diseases due to the expanding geographic range and seasonality of these diseases and their vectors. [61] : 9 Like other ways in which climate change affects on human health, climate change exacerbates existing inequalities and challenges in managing infectious disease.
Mosquito-borne diseases that are sensitive to climate include malaria, lymphatic filariasis, Rift Valley fever, yellow fever, dengue fever, Zika virus, and chikungunya. [62] [63] [64] Scientists found in 2022 that rising temperatures are increasing the areas where dengue fever, malaria and other mosquito-carried diseases are able to spread. [60] : 1062 Warmer temperatures are also advancing to higher elevations, allowing mosquitoes to survive in places that were previously inhospitable to them. [60] : 1045 This risks malaria making a return to areas where it was previously eradicated. [65]Air pollution generated by fossil fuel combustion is both a major driver of global warming and the cause of a large number of annual deaths with some estimates as high as 8.7 million excess deaths during 2018. [66] [67]
Indoor air pollution is known to affect the health, comfort, and well-being of building occupants. It has also been linked to sick building syndrome, respiratory issues, reduced productivity, and impaired learning in schools. Indoor air quality is linked inextricably to outdoor air quality. [68] Climate change can affect indoor air quality by increasing the level of outdoor air pollutants such as ozone and particulate matter. [69] Numerous predictions for how indoor air pollutants will change have been made, [70] [71] [72] [73] and models have attempted to predict how the forecasted scenarios will vary indoor air quality and indoor comfort parameters such as humidity and temperature. [74]
The net-zero challenge requires significant changes in the performance of both new and retrofitted buildings. However our increased energy efficient housing will trap pollutants inside them, whether produced indoors or outdoors, and lead to an increase in human exposure. [75] [76]
The relationship between surface ozone (also called ground-level ozone) and ambient temperature is complex. Changes in air temperature and water content affect the air's chemistry and the rates of chemical reactions that create and remove ozone. Many chemical reaction rates increase with temperature and lead to increased ozone production. Climate change projections show that rising temperatures and water vapour in the atmosphere will likely increase surface ozone in polluted areas like the eastern United States. [77]
On the other hand, ozone concentrations could decrease in a warming climate if anthropogenic ozone-precursor emissions (e.g., nitrogen oxides) continue to decrease through implementation of policies and practices. [78] Therefore, future surface ozone concentrations depend on the climate change mitigation steps taken (more or less methane emissions) as well as air pollution control steps taken. [79] : 884
High surface ozone concentrations often occur during heat waves in the United States. [78] Throughout much of the eastern United States, ozone concentrations during heat waves are at least 20% higher than the summer average. [78] Broadly speaking, surface ozone levels are higher in cities with high levels of air pollution. [79] : 876 Ozone pollution in urban areas affects denser populations, and is worsened by high populations of vehicles, which emit pollutants NO2 and VOCs, the main contributors to problematic ozone levels. [80]
There is a great deal of evidence to show that surface ozone can harm lung function and irritate the respiratory system. [81] [82] Exposure to ozone (and the pollutants that produce it) is linked to premature death, asthma, bronchitis, heart attack, and other cardiopulmonary problems. [83] [84] High ozone concentrations irritate the lungs and thus affect respiratory function, especially among people with asthma. [78] People who are most at risk from breathing in ozone air pollution are those with respiratory issues, children, older adults and those who typically spend long periods of time outside such as construction workers. [85]
Climate change affects many aspects of food security through "multiple and interconnected pathways". [2] : 1619 Many of these are related to the effects of climate change on agriculture, for example failed crops due to more extreme weather events. This comes on top of other coexisting crises that reduce food security in many regions. Less food security means more undernutrition with all its associated health problems. Food insecurity is increasing at the global level (some of the underlying causes are related to climate change, others are not) and about 720–811 million people suffered from hunger in 2020. [2] : 1629
The number of deaths resulting from climate change-induced changes to food availability are difficult to estimate. The 2022 IPCC Sixth Assessment Report does not quantify this number in its chapter on food security. [86] A modelling study from 2016 found "a climate change–associated net increase of 529,000 adult deaths worldwide [...] from expected reductions in food availability (particularly fruit and vegetables) by 2050, as compared with a reference scenario without climate change." [87] [88]
A headline finding in 2021 regarding marine food security stated that: "In 2018–20, nearly 70% of countries showed increases in average sea surface temperature in their territorial waters compared within 2003–05, reflecting an increasing threat to their marine food productivity and marine food security". [3] : 14 (see also climate change and fisheries).
A warming climate can lead to increases of pollen season lengths and concentrations in some regions of the world. For example, in northern mid-latitudes regions, the spring pollen season is now starting earlier. [1] : 1049 This can affect people with pollen allergies (hay fever). [92] The rise in pollen also comes from rising CO2 concentrations in the atmosphere and resulting CO2 fertilisation effects. [1] : 1096
The warming oceans and lakes are leading to more frequent harmful algal blooms. [100] [101] [102] Also, during droughts, surface waters are even more susceptible to harmful algal blooms and microorganisms. [103] Algal blooms increase water turbidity, suffocating aquatic plants, and can deplete oxygen, killing fish. Some kinds of blue-green algae (cyanobacteria) create neurotoxins, hepatoxins, cytotoxins or endotoxins that can cause serious and sometimes fatal neurological, liver and digestive diseases in humans. Cyanobacteria grow best in warmer temperatures (especially above 25 degrees Celsius), and so areas of the world that are experiencing general warming as a result of climate change are also experiencing harmful algal blooms more frequently and for longer periods of time. [104]
One of these toxin producing algae is Pseudo-nitzschia fraudulenta. This species produces a substance called domoic acid which is responsible for amnesic shellfish poisoning. [105] [106] The toxicity of this species has been shown to increase with greater CO2 concentrations associated with ocean acidification. [105] Some of the more common illnesses reported from harmful algal blooms include; Ciguatera fish poisoning, paralytic shellfish poisoning, azaspiracid shellfish poisoning, diarrhetic shellfish poisoning, neurotoxic shellfish poisoning and the above-mentioned amnesic shellfish poisoning. [105]
It is possible that a potential health benefit from global warming could result from fewer cold days in winter: [1] : 1099 This could lead to some mental health benefits. However, the evidence on this correlation is regarded as inconsistent in 2022. [1] : 1099
The potential health benefits (also called "co-benefits") from climate change mitigation and adaptation measures are significant, having been described as "the greatest global health opportunity" of the 21st century. [8] : 1861 Measures can not only mitigate future health effects from climate change but also improve health directly. [107] Climate change mitigation is interconnected with various co-benefits (such as reduced air pollution and associated health benefits) [108] and how it is carried out (in terms of e.g. policymaking) could also determine its effect on living standards (whether and how inequality and poverty are reduced). [109]
There are many health co-benefits associated with climate action. These include those of cleaner air, healthier diets (e.g. less red meat), more active lifestyles, and increased exposure to green urban spaces. [3] : 26 Access to urban green spaces provides benefits to mental health as well. [3] : 18
Biking reduces greenhouse gas emissions [110] while reducing the effects of a sedentary lifestyle at the same time [111] According to PLoS Medicine: "obesity, diabetes, heart disease, and cancer, which are in part related to physical inactivity, may be reduced by a switch to low-carbon transport—including walking and cycling." [112]
Compared with the current pathways scenario (with regards to greenhouse gas emissions and mitigation efforts), the sustainable pathways scenario will likely result in an annual reduction of 1.18 million air pollution-related deaths, 5.86 million diet-related deaths, and 1.15 million deaths due to physical inactivity, across the nine countries, by 2040. These benefits were attributable to the mitigation of direct greenhouse gas emissions and the commensurate actions that reduce exposure to harmful pollutants, as well as improved diets and safe physical activity. [113]
Climate change mitigation policies can lead to lower emissions of co-emitted air pollutants, for instance by shifting away from fossil fuel combustion. Gases such as black carbon and methane contribute both to global warming and to air pollution. Their mitigation can bring benefits in terms of limiting global temperature increases as well as improving air quality. [114] Implementation of the climate pledges made in the run-up to the Paris Agreement could therefore have significant benefits for human health by improving air quality. [115]
The replacement of coal-based energy with renewables can lower the number of premature deaths caused by air pollution and decrease health costs associated with coal-related respiratory diseases. This switch to renewable energy is crucial, as air pollution is responsible for over 13 million deaths annually. [116] [117]
Estimating deaths (mortality) or DALYs (morbidity) from the effects of climate change at the global level is very difficult. A 2014 study by the World Health Organization estimated the effect of climate change on human health, but not all of the effects of climate change were included. [119] For example, the effects of more frequent and extreme storms were excluded. The study assessed deaths from heat exposure in elderly people, increases in diarrhea, malaria, dengue, coastal flooding, and childhood undernutrition. The authors estimated that climate change was projected to cause an additional 250,000 deaths per year between 2030 and 2050 but also stated that "these numbers do not represent a prediction of the overall impacts of climate change on health, since we could not quantify several important causal pathways". [119]
Climate change was responsible for 3% of diarrhoea, 3% of malaria, and 3.8% of dengue fever deaths worldwide in 2004. [120] Total attributable mortality was about 0.2% of deaths in 2004; of these, 85% were child deaths. The effects of more frequent and extreme storms were excluded from this study.
The health effects of climate change are expected to rise in line with projected ongoing global warming for different climate change scenarios. [121] [122] A review [123] found if warming reaches or exceeds 2 °C this century, roughly 1 billion premature deaths would be caused by anthropogenic global warming. [124]
A 2021 report published in The Lancet found that climate change does not affect people's health in an equal way. The greatest impact tends to fall on the most vulnerable such as the poor, women, children, the elderly, people with pre-existing health concerns, other minorities and outdoor workers. [3] : 13
The social vulnerability of people is related to certain health patterns. For example there are "demographic, socioeconomic, housing, health (such as pre-existing health conditions), neighbourhood, and geographical factors". [125]
Much of the health burden associated with climate change falls on vulnerable people (e.g. indigenous peoples and economically disadvantaged communities). As a result, people of disadvantaged sociodemographic groups experience unequal risks. [126] Often these people will have made a disproportionately low contribution toward man-made global warming, thus leading to concerns over climate justice. [127] [128] [122]
Climate change has diverse effects on migration activities, and can lead to decreases or increases in the number of people who migrate. [1] : 1079 Migration activities can have an effect on health and well-being, in particular for mental health. Migration in the context of climate change can be grouped into four types: adaptive migration (see also climate change adaptation), involuntary migration, organised relocation of populations, and immobility (which is when people are unable or unwilling to move even though it is recommended). [1] : 1079
The observed contribution of climate change to conflict risk is small in comparison with cultural, socioeconomic, and political causes. There is some evidence that rural-to-urban migration within countries worsens the conflict risk in violence prone regions. But there is no evidence that migration between countries would increase the risk of violence. [1] : 1008, 1128
Studies have found that when communicating climate change with the public, it can help encourage engagement if it is framed as a health concern, rather than as an environmental issue. This is especially the case when comparing a health related framing to one that emphasised environmental doom, as was common in the media at least up until 2017. [129] [130] Communicating the co-benefits to health helps underpin greenhouse gas reduction strategies. [37] Safeguarding health—particularly of the most vulnerable—is a frontline local climate change adaptation goal. [37]
In 2019, the Australian Medical Association formally declared climate change as a health emergency. [131]
Due to its significant impact on human health, [133] [134] climate change has become a major concern for public health policy. The United States Environmental Protection Agency had issued a 100-page report on global warming and human health back in 1989. [122] [135] By the early years of the 21st century, climate change was increasingly addressed as a public health concern at a global level, for example in 2006 at Nairobi by UN secretary general Kofi Annan. Since 2018, factors such as the 2018 heat wave, the Greta effect and the IPCC's 2018 Special Report on Global Warming of 1.5 °C further increased the urgency for responding to climate change as a global health issue. [122] [37] [128]
The World Bank has suggested a framework that can strengthen health systems to make them more resilient and climate-sensitive. [136]
Placing health as a key focus of the Nationally Determined Contributions could present an opportunity to increase ambition and realize health co-benefits. [113]
Ozone is an inorganic molecule with the chemical formula O
3. It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope O
2, breaking down in the lower atmosphere to O
2 (dioxygen). Ozone is formed from dioxygen by the action of ultraviolet (UV) light and electrical discharges within the Earth's atmosphere. It is present in very low concentrations throughout the atmosphere, with its highest concentration high in the ozone layer of the stratosphere, which absorbs most of the Sun's ultraviolet (UV) radiation.
Urban areas usually experience the urban heat island (UHI) effect, that is, they are significantly warmer than surrounding rural areas. The temperature difference is usually larger at night than during the day, and is most apparent when winds are weak, under block conditions, noticeably during the summer and winter. The main cause of the UHI effect is from the modification of land surfaces while waste heat generated by energy usage is a secondary contributor. A study has shown that heat islands can be affected by proximity to different types of land cover, so that proximity to barren land causes urban land to become hotter and proximity to vegetation makes it cooler. As a population center grows, it tends to expand its area and increase its average temperature. The term heat island is also used; the term can be used to refer to any area that is relatively hotter than the surrounding, but generally refers to human-disturbed areas. Urban areas occupy about 0.5% of the Earth's land surface but host more than half of the world's population.
Extreme weather includes unexpected, unusual, severe, or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Extreme events are based on a location's recorded weather history. They are defined as lying in the most unusual ten percent. The main types of extreme weather include heat waves, cold waves and heavy precipitation or storm events, such as tropical cyclones. The effects of extreme weather events are economic costs, loss of human lives, droughts, floods, landslides. Severe weather is a particular type of extreme weather which poses risks to life and property.
Ground-level ozone (O3), also known as surface-level ozone and tropospheric ozone, is a trace gas in the troposphere (the lowest level of the Earth's atmosphere), with an average concentration of 20–30 parts per billion by volume (ppbv), with close to 100 ppbv in polluted areas. Ozone is also an important constituent of the stratosphere, where the ozone layer (2 to 8 parts per million ozone) exists which is located between 10 and 50 kilometers above the Earth's surface. The troposphere extends from the ground up to a variable height of approximately 14 kilometers above sea level. Ozone is least concentrated in the ground layer (or planetary boundary layer) of the troposphere. Ground-level or tropospheric ozone is created by chemical reactions between NOx gases (oxides of nitrogen produced by combustion) and volatile organic compounds (VOCs). The combination of these chemicals in the presence of sunlight form ozone. Its concentration increases as height above sea level increases, with a maximum concentration at the tropopause. About 90% of total ozone in the atmosphere is in the stratosphere, and 10% is in the troposphere. Although tropospheric ozone is less concentrated than stratospheric ozone, it is of concern because of its health effects. Ozone in the troposphere is considered a greenhouse gas, and may contribute to global warming.
Indoor air quality (IAQ) is the air quality within buildings and structures. Poor indoor air quality due to indoor air pollution is known to affect the health, comfort, and well-being of building occupants. It has also been linked to sick building syndrome, respiratory issues, reduced productivity, and impaired learning in schools. Common pollutants of indoor air include: secondhand tobacco smoke, air pollutants from indoor combustion, radon, molds and other allergens, carbon monoxide, volatile organic compounds, legionella and other bacteria, asbestos fibers, carbon dioxide, ozone and particulates. Source control, filtration, and the use of ventilation to dilute contaminants are the primary methods for improving indoor air quality.
A heat wave, sometimes described as extreme heat, is a period of abnormally hot weather. Definitions vary but are similar. A heat wave is usually measured relative to the usual climate in the area and to normal temperatures for the season. Temperatures that humans from a hotter climate consider normal, can be regarded as a heat wave in a cooler area. This would be the case if the warm temperatures are outside the normal climate pattern for that area. High humidity often occurs during heat waves as well. This is especially the case in oceanic climate countries. Heat waves have become more frequent, and more intense over land, across almost every area on Earth since the 1950s. Heat waves occur from climate change.
Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack, or propelling nozzle. It often disperses downwind in a pattern called an exhaust plume.
Human impact on the environment refers to changes to biophysical environments and to ecosystems, biodiversity, and natural resources caused directly or indirectly by humans. Modifying the environment to fit the needs of society is causing severe effects including global warming, environmental degradation, mass extinction and biodiversity loss, ecological crisis, and ecological collapse. Some human activities that cause damage to the environment on a global scale include population growth, neoliberal economic policies and rapid economic growth, overconsumption, overexploitation, pollution, and deforestation. Some of the problems, including global warming and biodiversity loss, have been proposed as representing catastrophic risks to the survival of the human species.
Effects of climate change are well documented and growing for Earth's natural environment and human societies. Changes to the climate system include an overall warming trend, changes to precipitation patterns, and more extreme weather. As the climate changes it impacts the natural environment with effects such as more intense forest fires, thawing permafrost, and desertification. These changes impact ecosystems and societies, and can become irreversible once tipping points are crossed.
African environmental issues are caused by human impacts on the natural environment and affect humans and nearly all forms of life. Issues include deforestation, soil degradation, air pollution, water pollution, garbage pollution, climate change and water scarcity. These issues result in environmental conflict and are connected to broader social struggles for democracy and sovereignty.
Air pollution is the contamination of air due to the presence of substances called pollutants in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. It is also the contamination of the indoor or outdoor environment either by chemical, physical, or biological agents that alters the natural features of the atmosphere. There are many different types of air pollutants, such as gases, particulates, and biological molecules. Air pollution can cause diseases, allergies, and even death to humans; it can also cause harm to other living organisms such as animals and crops, and may damage the natural environment or built environment. Air pollution can be caused by both human activities and natural phenomena.
Climate change in California has resulted in higher than average temperatures, leading to increased occurrences of drought and wildfires. During the next few decades in California, climate change is likely to further reduce water availability, increase wildfire risk, decrease agricultural productivity, and threaten coastal ecosystems. The state will also be impacted economically due to the rising cost of providing water to its residents along with revenue and job loss in the agricultural sector. California has taken a number of steps to mitigate impacts of climate change in the state.
Particulates or atmospheric particulate matter are microscopic particles of solid or liquid matter suspended in the air. The term aerosol commonly refers to the particulate/air mixture, as opposed to the particulate matter alone. Sources of particulate matter can be natural or anthropogenic. They have impacts on climate and precipitation that adversely affect human health, in ways additional to direct inhalation.
There are numerous effects of climate change on agriculture, many of which are making it harder for agricultural activities to provide global food security. Rising temperatures and changing weather patterns often result in lower crop yields due to water scarcity caused by drought, heat waves and flooding. These effects of climate change can also increase the risk of several regions suffering simultaneous crop failures. Currently this risk is regarded as rare but if these simultaneous crop failures did happen they would have significant consequences for the global food supply. Many pests and plant diseases are also expected to either become more prevalent or to spread to new regions. The world's livestock are also expected to be affected by many of the same issues, from greater heat stress to animal feed shortfalls and the spread of parasites and vector-borne diseases.
The effects of climate change on mental health and wellbeing are documented. This is especially the case for vulnerable populations and those with pre-existing serious mental illness. There are three broad pathways by which these effects can take place: directly, indirectly or via awareness. The direct pathway includes stress-related conditions caused by exposure to extreme weather events. These include post-traumatic stress disorder (PTSD). Scientific studies have linked mental health to several climate-related exposures. These include heat, humidity, rainfall, drought, wildfires and floods. The indirect pathway can be disruption to economic and social activities. An example is when an area of farmland is less able to produce food. The third pathway can be of mere awareness of the climate change threat, even by individuals who are not otherwise affected by it.
Environmental health policy is governmental action intended to prevent exposure to environmental hazards or "eliminate the effects of exposure to environmental hazards".
Global climate change has increased the occurrence of some infectious diseases. Infectious diseases whose transmission is impacted by climate change include, for example, vector-borne diseases like dengue fever, malaria, tick-borne diseases, leishmaniasis, zika fever, chikungunya and Ebola. One mechanism contributing to increased disease transmission is that climate change is altering the geographic range and seasonality of the insects that can carry the diseases. Scientists stated a clear observation in 2022: "the occurrence of climate-related food-borne and waterborne diseases has increased ."
Children are more vulnerable to the effects of climate change than adults. The World Health Organization estimated that 88% of the existing global burden of disease caused by climate change affects children under five years of age. A Lancet review on health and climate change lists children as the worst-affected category by climate change. Children under 14 are 44 percent more likely to die from environmental factors, and those in urban areas are disproportionately impacted by lower air quality and overcrowding.
Triple Planetary Crisis is a term and framework adopted by the United Nations system to describe the three intersecting global environmental crises of pollution, climate crisis, biodiversity loss and/or ecological crises. This term underscores the interdependence of these issues and their collective impact on the planet's ecosystems, societies, and economies.