Traditionally Climate Change has arisen concerns mostly related to its impact on natural resources and subsequent economic burden. The direct impact on human health has been substantially neglected in public debate. However, the release of the second part of IPCC Fifth Assessment Report last March kicked off a public debate on the multifaceted effects of climate change that takes health into account.
The IPCC report describes in detail, based on the most recent evidence, three pathways by which climate change affects health: direct impacts, ecosystem mediated impacts and impacts mediated through human systems.
The direct impacts of climate change are caused mainly by weather extreme events. Floods cause drowning, hypothermia, injuries and mental health problems in the short and long term. The rise of urbanization in low latitude hot countries leads people to live in overcrowded urban settlements, with poor ventilation, isolation and drainage, increasing their vulnerability to extreme temperatures and floods. People already living in hot areas and urban heat islands, can face temperatures that compromise human thermoregulation, putting them at risk of organ damage, circulatory collapse, loss of consciousness and death.
The ecosystem-mediated health impacts are related to infectious diseases and air quality. Changes in temperature and rainfall modify the distribution and life cycle of vectors, such as mosquitoes or ticks, which transmit diseases such as Malaria or Chagas. Heavy rainfall creates puddles of stagnant water that can become mosquito breeding sites. Incubation periods and vector´s life cycle shorten with increasing temperature and can lead to an increase in transmission. Water-borne diseases are also sensitive to temperature and rainfall. Run-off can cause contamination of water from fecal waste and higher temperature increases pathogen proliferation. More areas are expected to become suitable for infectious diseases transmission, which will put more people at risk.
Climate-altering pollutants (CAPs) not only affect health through climate change but also directly. 7.6% of total disability-adjusted life years (DALYs) are attributable to particle air pollution, putting air pollution at the top of the list of environmental health risk factors. Reducing air pollution is one of the greatest challenges that human beings face. WHO estimates that the international community ought to be willing to pay 2.7% of the world’s total economy to reduce it.
Impacts mediated through human systems refer to impacts on nutrition and occupational health. Under the best scenario child underweight could be 20% higher by 2050 due to lower crop yields, hampering efforts towards the achievement of the first MDG. Climate change will increase hazards at the workplace. Heat will make people shift their working time from day time to dawn and dusk, when some vectors are more active, putting them at risk of infectious diseases. Higher temperature will cause the evaporation of toxic chemicals that can cause poisoning and respiratory diseases. Under a scenario of a 3.4 ºC increase in temperature by 2100, productivity is estimated to be reduced by 60%.
Climate change affects health in evident and no evident ways, whose scope we need to understand. It is necessary to reflect on these pathways and start including health in climate change adaptation strategies and health policies. Once, we refused the existence of climate change, now, we don´t want to incur in the error of neglecting its effects on health.
Lucía Fernández holds a degree in Physical Sciences and is now completing the ISGlobal-UB Master of Clinical Research - International Health Track.
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