In response to global warming, humans have been forced to adapt in response to the long-term warming trend. Long-term warming is concomitant with severe weather events such as heat waves, cold spells, extreme precipitation or storms. One adaptation to extreme heat events is the installation of air conditioning (along with heating and ventilation) in homes and public buildings around the world.
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What do we know about the effects of air conditioning on health?
Current knowledge about the health effects of air conditioning is based on studies of office workers or on exercise-related heat-related illness. In addition, artificial experimental designs on climatic influences on physiology have also been carried out.
Despite this, studies on the effects of air conditioning on health are scarce and there is a lack of knowledge on how the mechanisms affect the health of patients.
To review the available literature, an article published in BMC public health analyzed the available evidence published in Medline, Embase and the Cochrane Library. This review focused specifically on inpatients and results were recorded based on intervention, population, control, and outcome.
This literature also reviewed all of the studies that examined the effect of heating and ventilation alongside air conditioning. Collectively, the publication refers to these modes of air and temperature adaptation as heating, ventilating and air conditioning (HVAC).
Overall, CVC improves recovery, including improving vital signs, reducing incidents of cardiac stress, speeding recovery, and promoting greater physical activity. Additionally, the use of CVC has reduced mortality in patients with heat-related illnesses and resulted in shorter hospital stays for patients with respiratory illnesses.
Therefore, in the inpatient setting, the installation of CVCs has the potential to improve patient outcomes and increase the effectiveness of inpatient treatment. This is particularly noticeable in mitigating the effects of climate change on health and health systems.
Air conditioning in the context of epidemics and pandemics
Since the COVID-19 pandemic, the mode of spread of the SARS-CoV-2 virus has been widely studied. The virus is known to be spread primarily through close contact, especially when an infected person coughs, talks, sneezes or uses their voice at short distances
In addition, airborne transmission of the virus can occur during medical procedures that produce aerosols. As such, preventive measures have been put in place. The transmission capacity of aerosol-generating procedures is also dependent on particles, as they can release toxic molecules and microorganisms, including viruses. As such, ventilation systems, including heating and air conditioning, which involve the recirculation of exhaust air were reviewed.
Along with respiratory viruses (influenza and coronavirus), other microorganisms such as vegetative bacteria (staphylococci and legionella), fungi, (Aspergillus and Penicillium), mycobacteria (tuberculous and non-tuberculous), enteric viruses (noro- and rotavirus) and bacterial sporulants (Clostridium difficile and Bacillus anthracis), can also be spread by air. The virality of these pathogens depends on air temperature, relative humidity, and turbulence, among other factors.
As such, air conditioning can spread these pathogenic bacteria, especially when the air conditioners do not have an effective filtration system. In addition, the risk of infections caused by air conditioning increases as the size of the ventilated room increases (making it high in public places like department stores, airplanes, ships and hospitals).
This is exacerbated because air conditioners do not cool the hot air coming from the outside, but rather recirculate the indoor air to keep it cool. This results in a significant reduction in air exchange while increasing the concentration of pollutants and infectious agents that can exacerbate their pathogenic activity due to the favorable effects of artificially cold and dry air.
Impact of air conditioning on respiratory health
Air conditioning can lead to increased clinical discomfort in those who last have respiratory illnesses. In case of chronic respiratory disease, there is a risk of worsening symptoms. Additionally, respiratory infections can be caused by cold air due to increased bronchial inflammation which works alongside other triggers such as infection, inhalation of pollutants, cigarette smoke, and irritants. present in the air.
In healthy people, exposure to very cold air conditioners can cause damage to the airways which, in pre-existing conditions such as asthma, can increase the risk of developing respiratory disease.
Under conditions where the air temperature drops rapidly, even for small changes between but more markedly for changes of more than 5 ° C, there is a possible negative consequence exerted on the respiratory system. This effect is more pronounced in people with obstructive respiratory diseases such as asthma and COPD. Cold air is also known to trigger bronchoconstriction in asthmatics
The effect of air conditioners on cognitive performance
Research from the Harvard Chan School of Public Health has shown that rising indoor temperatures during a heat wave produced adverse cognitive effects in a group of healthy young people without air conditioning. The study followed 44 students at a Massachusetts university living in air-conditioned and non-air conditioned buildings before, during and after a heat wave.
The participants were subjected to two cognitive tests and the effect of the heat wave on cognitive function was assessed. The group found that cognitive function deficits resulted from indoor thermal conditions caused by heat waves in non-air conditioned buildings. The researchers suggested that this decline in cognitive function could be attributed to increased heat load and the exacerbated effects of other environmental and behavioral factors.
This corroborates existing experimental, epidemiological and econometric studies which have shown that heat exposure can negatively affect productivity, learning ability, mortality and mobility in humans.
Other positive health impacts of air conditioners
Air conditioning critically maintains body temperature. This is essential in humid and warm parts of the world where heat stroke is a significant problem during the peak of summer. Although humans can acclimatize to hot environments, this usually happens over a long period of time (7-14 days with at least two hours of daily exposure to heat) and it is possible for people to lose their acclimatization to heat when they spend most of their time in air. conditioned environments. They then have a harder time re-acclimatizing in the future.
Air conditioners are also useful in facilitating sleep by triggering homeostatic mechanisms to cool the body. Air conditioners can also decrease the incidence of allergic reactions because, if air conditioners are confined to small spaces in which air is exchanged with the outdoors, all allergens can be removed.
The references:
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- Chirico F, Sacco A, Bragazzi NL, et al. (2020) Can air conditioning systems contribute to the spread of SARS / MERS / COVID-19 infection? Insights from a quick review of the literature. Int J Environ Public Health Res. doi: 10.3390 / ijerph17176052.
- Cedeño Laurent JG, Williams A, et al. (2018) Reduced cognitive function during a heat wave among residents of non-air conditioned buildings: an observational study of young adults in the summer of 2016. PLoS Med. doi: 10.1371 / journal.pmed.1002605.
- D’Amato M, Molino A, Calabrese G, et al. (2018) The impact of cold on the respiratory tract and its consequences on respiratory health. Clin Transl Allergy. doi: 10.1186 / s13601-018-0208-9.
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