The human exposome and health in the Anthropocene

‘Man is a part of nature, and his war against nature is inevitably a war against himself’ ― Rachel Carson. The term Anthropocene describes the current period, when the biophysical systems of Earth are being significantly altered by human activities. Although the great acceleration of anthropogenic influences began in the 20th century, the Industrial Revolution has often been proposed as the start of this period. Burning fossil fuels on a large scale, which was the motor of the Industrial Revolution, has disrupted the global climate, with far-reaching consequences for life on Earth. In the Intergovernmental Panel on Climate Change (IPCC) Special Report, it is stated with high confidence that human activities have significantly contributed to an increase in the global mean temperature of approximately 1°C above pre-industrial levels, and with medium confidence that trends in intensity and frequency of some climate and weather extremes have been detected, during which approximately 0.5°C of global warming occurred.1 The average global temperature will continue to rise if current greenhouse gas emissions continue. The Copernicus Climate Change Service (C3S) recently reported that the 5 warmest years on record have all occurred in the past 5 years, and that 2010–19 was the warmest decade recorded. C3S also reported that 2019 was globally the second warmest year and that atmospheric carbon dioxide (CO2) concentrations continued to rise.2 During 2019 there was extraordinary ice-melt in Greenland and wildfires consumed millions of acres in Siberia, Alaska and Australia.3,4 Brazil’s national institute for space research (INPE) also reported fires burning at a record rate in the Amazon rainforest. The INPE reported an 80% increase in deforestation compared with that in the same period in 2018. This not only threatens local ecosystems but may affect the entire planet, because intact forest absorbs and holds large amounts of CO2.5 The recent Living Planet Report by the World Wildlife Fund and Zoological Society of London provides further evidence that unsustainable human activity is threatening the planet’s natural systems.6 The report shows an overall decline of 60% in species’ population sizes between 1970 and 2014 because of factors such as overexploitation, habitat destruction (e.g. agricultural land expansion and logging), environmental pollution and climate change. The current species extinction rates are between 100 and 1000 times higher than previous background rate.6 The International Union for Conservation of Nature Red List 2019 reported that more than 27 000 species are threatened with extinction (27% of all animal, fungi and plant species assessed).7 A recent study of plants that have become extinct since Carl Linnaeus’ Species Plantarum has concluded that the number of known seed plant extinctions is more than four times that of the Red List.8 Biodiversity is a vital part of Earth’s past, present and future, and a key indicator of planetary health. The ongoing dramatic decline in biodiversity is therefore a problem, and underlying causes must be better understood for effective species conservation and human well-being. The concept of planetary health focuses on the intricate link between human health and the health of natural systems within the biosphere.9–11 Loss of biological diversity alters ecosystems functions and thereby reduces the ability to provide society with the goods and services, including food, necessary to flourish.9–11 The emergence of viruses such as the novel coronavirus (SARS-CoV-2), and global environmental change, wildlife, animal markets and food systems (which contribute largely to carbon emissions) are also interrelated.12,13 To increase awareness of current environmental problems and how complex interactions among climate change, infectious agents, environmental pollutants and other stressors, i.e. the exposome, may affect human health, this multidisciplinary review summarizes important scientific literature and discusses actions for a successful transformation to a safe, sustainable society. Climate is defined as the long-term average of the state of the atmosphere or the oceans; thus extended data records are necessary to establish climate change and to distinguish the differences within the natural variability of the climate system. One of the world’s longest temperature records was started in 1722 in Uppsala, Sweden, by Professor Erik Burman with support from the young Anders Celsius. Figures 1 and 2 show the annual mean temperature and seasonal mean temperatures in Uppsala from 1722 to 2019, based on this unique temperature record. The warming of the past decades is evident especially during spring; the large natural temperature variability is also observed. Annual mean temperature in Uppsala, Sweden, from 1722 to 2019. Annual data (black dots), 5 years running mean (black line) and 30 years running mean (grey line), dotted parts of the lines indicate fewer representative means (because of shorter time periods for the running means). Data processing according to Bergström and Moberg (2002)15 Seasonal mean temperature in Uppsala, Sweden, from 1722 to 2019. Annual data (black dots), 5 years running mean (black line) and 30 years running mean (grey line), dotted parts of the lines indicate fewer representative means (because of shorter time periods for the running means). Data processing according to Bergström and Moberg (2002)15 The rapid growth of the human population and human activities are causing a problem: the increased pressure is destabilizing critical biophysical Earth systems and triggering environmental changes that are deleterious and catastrophic for human well-being.16 This is a dilemma, as the main paradigm of socioeconomic development remains largely oblivious to the risk of human-induced environmental disasters on continental to planetary scales.16,17 Between 1750 and 2011, cumulative anthropogenic CO2 emissions into the atmosphere were 2040 ± 310 GtCO2. The increase in CO2 is mainly due to burning of fossil fuels and deforestation. Approximately 40% of these emissions remain in the atmosphere; the remainder have been removed and stored on land or in the ocean, where the oceans have absorbed approximately 30% of the emitted anthropogenic CO2, causing ocean acidification.4,18 Nobel Prize Laureate Svante Arrhenius was the first to estimate the influence of atmospheric CO2 levels—the greenhouse effect—on Earth’s temperature, and is arguably the father of climate change science.19,20 Increased concentrations of CO2 and other greenhouse gases in the atmosphere affect the global climate, and regional climate in different parts of the world.18 The consequences are clearly shown for temperature, where each of the past four decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. The global average combined land and ocean surface temperature data show warming of 0.85°C from 1880 to 2012. There are, however, large regional variations, with an amplification towards the Arctic areas; for example, for the Baltic Sea region, where the corresponding increase was well over 1°C.21 Warming induces changes in other crucial parameters such as precipitation, sea level, icemelt and snowmelt. A shift in the extent and the frequency of some types of extreme weather events has also been observed.18 Some areas have experienced increased frequencies of droughts and heatwaves, and other areas an increased risk of flooding. These events have consequences for forest fires, infrastructure and water availability, for example. The potential increase in extreme conditions and the possibility of ‘tipping points’, that is threshold barriers implying that it would be impossible for the considered system to restore to a healthy point, is a serious risk for society. Human activities risk triggering biosphere tipping points across a range of systems, which could induce cascade effects that further amplify ongoing environmental changes. For example, with the rapid Arctic warming, permafrost is starting to irreversibly thaw and release CO2 and the more potent greenhouse gas, methane (CH4).22 The subarctic boreal forest is also increasingly vulnerable; warming has triggered large-scale insect disturbances and an increase in wildfires that have led to forest dieback, potentially changing some areas from a carbon sink to a carbon source.23 Furthermore, Arctic warming and Greenland ice melting are drivers of an influx of freshwater into the North Atlantic, which may have contributed to the observed weakening of the Atlantic Meridional Overturning Circulation (AMOC), a system of currents central to global heat and salt transport.4,24 Continued melting of the Greenland ice sheet and further AMOC weakening may destabilize, for example, the West African monsoon, causing drought in Africa’s Sahel region. A slowdown in the AMOC also might dry the Amazon, disrupt the East Asian monsoon and warm the Southern Ocean, which may then increase Antarctic ice loss.22 Climate change affects human health too. Notably, projections have indicated that one to three billion individuals will reside outside the climate conditions that have served humanity well for the past 6000 years.25 As a ripple-down effect, health consequences of climate change can be direct, for example the high deaths tolls among elderly, isolated and disadvantaged populations that occur because of heatwaves. The health consequences can also be more complex, such as effects of floods beyond accidents and drownings, including water and vector-borne infectious outbreaks, displacement and socioeconomic impacts, allergic reactions to mould and increase in damp conditions, and macronutrient or micronutrient undernutrition. The 2018 report of the Lancet countdown on health and climate change presents how planetary health is developing in the natural, social and human health domains.26 It finds that the increase in the actual average temperature that people are experiencing is greater than the global increase because temperatures are rising more rapidly in densely populated locations (e.g. large cities). In some respects, vulnerability to heat is also increasing, for instance due to the ageing of populations.26 Recent climate change projections indicate that worldwide, the residents of the North China Plain, one of the world’s most densely populated areas, are at greatest risk of deaths from heatwaves.27 The study suggests that the risk of deadly heatwaves is significantly increased because of intensive irrigation, which increases humidity and amplifies heat stress in this naturally dry The potential of vector-borne such as and also increases as a of climate change, mainly due to increased higher and of the has recently experienced an increase in the number of such by changing climate conditions and human and to these A increase has been observed for by species that in warmer on and the of potential effects is to biodiversity and human health. which environmental are and interactions with biological systems is therefore In Rachel an and from the which is with to the environmental and 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