The determinants of health include genetic, behavioural and social factors; adequate supplies of clean air, water, food and hygienic sanitation; and exposure to microorganisms, toxins and environmental hazards.
Population growth was slow and life expectancy was low until about two centuries ago.
Changes to these two areas were possible in part because of the use of energy from fossil fuels.
It is increasingly being recognised that the combustion of fossil fuels has led to global warming, which is posing unprecedented threats to human health with its impacts on water and food security, floods, droughts, violent storms, heat waves, rising sea levels and infectious diseases.
The climate change debate has been ongoing for about a quarter century now and its impact on health is increasingly being recognised.
The direct impact of air and environmental pollution is manifested obviously in increasing respiratory disorders and allergies.
However, there are other less obvious impacts of climate change on health.
The changes in the environment and various ecosystems have caused changes in the patterns of disease-carrying vectors (like mosquitoes and bats) and new infectious diseases.
It is possible that these changes have led to the emergence of new microorganisms that cause infectious diseases in humans, e.g. the 1998 Nipah outbreak and the current Covid-19 pandemic.
Extremes of temperature can cause heat exhaustion, hyperthermia and hypothermia at the local level.
The forest fires, floods, droughts, hurricanes and tornados occurring around the world have resulted in injuries to both humans and animals, air and water pollution, spread of disease, mental health disorders, forced migration and population displacement, and death.
Altered agricultural and animal production have also impacted on health indirectly.
The effects include new infectious diseases, malnutrition and undernutrition.
The poor and disadvantaged groups in almost all countries, especially poorer ones, are the most adversely affected by the effects of climate change on health.
In particular, poor children are the most affected by climate-related diseases like water-borne infections, malaria, etc.
Burning it up
Jet fuel use is a major contributor to global carbon dioxide emissions.
The International Air Transport Association (IATA) estimated that global commercial aviation emitted about 905 million tonnes of carbon dioxide in 2018.
If commercial aviation were a country, it would rank sixth, after Japan, in terms of carbon dioxide emissions.
This is due to the exponential growth in air travel over the past three decades.
Although there have been improvements in the fuel efficiency of aeroplanes, the increased number of flights have more than countered the impact of the former on greenhouse emissions.
A 2018 paper in the journal Environmental Impact Assessment Review estimated that between 1990 and 2014, the global burning of jet fuel from civil aviation increased by 86%, while a White Paper published last September (2020) by the International Council on Clean Transportation reported that carbon dioxide emissions had increased by 44% from 2008 to 2018.
About one-fifth of emissions from commercial aviation came from passengers in premium seating classes, i.e. first and business class.
Depending on the aircraft type, premium seating was found to emit between 2.6 and 4.3 times more carbon dioxide than economy seating.
The United States Energy Information Administration estimates that jet fuel produces 9.57kg of carbon dioxide per gallon burnt.
A Boeing 737, which is the workhorse of many local and regional flights, burns an average of 750 gallons an hour.
In an one-hour flight from Kuala Lumpur to any of the regional cities of the Peninsula, the carbon dioxide produced would be 7,177.5kg.
Assuming there are 120 passengers (75% seating capacity) on the flight, the carbon dioxide produced per passenger would be 59.81kg.
On the other hand, a similar trip on the Learjet 40XR, which seats seven to eight people and is available for charter in Malaysia, burns about 640lbs (76.69 gallons) of jet fuel in an hour, producing 947.43kg of carbon dioxide.
Assuming there are eight passengers, the carbon dioxide produced per passenger would be 118.43kg.
In short, there is more carbon dioxide emission per passenger in a private jet than a commercial one; and more from a passenger in premium class than in economy class.
Assessing travel need
Effective action is needed, without which carbon dioxide emissions will lead to substantial increases in illness and death from diseases related to poor air quality, heat, reduced food quality and security, and increases in some infectious diseases, especially those that are vector-borne.
Humans are social beings.
Physical meetings contribute to the establishment of new relationships and enhancement of existing ones, thereby facilitating business, scientific and other human transactions.
Almost every government and institution worldwide is talking about a new normal due to Covid-19. But what does it mean for air travel?
It would be reasonable for everyone involved to ask what is to be gained from air travel and whether the objectives of such travel could be met without such travel, i.e. electronically.
There needs to be a refocusing to less travel for short meetings and an emphasis on higher value travel, with priority on the building of long-term institutional partnerships and co-operation.
Although air travel is experiencing a temporary glitch due to the Covid-19 pandemic, it is likely to increase in the post-Covid period with further increases in carbon dioxide emissions.
While global health and sustainable development need more international collaboration, there is also a pressing need to reduce carbon dioxide emissions.
The onus is on leaders, particularly in government and institutions, to lead by example, and not rhetoric.
Former World Health Organization (WHO) director-general Margaret Chan stated in 2015: “The evidence is overwhelming; climate change endangers human health.
“Solutions exist and we need to act decisively to change this trajectory.”
The jury is out as to whether or not carbon dioxide emissions can be reduced rapidly enough to slow climate change to a rate that human health will not be affected.
Dr Milton Lum is a past president of the Federation of Private Medical Practitioners Associations and the Malaysian Medical Association. For more information, email firstname.lastname@example.org. The views expressed do not represent that of organisations the writer is associated with. The information provided is for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regarding the reader’s own medical care. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.