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Heat, Disease, Air Pollution: How Climate Change Impacts Health

Air pollution, such as the extremes seen in India's capital New Delhi, are just one way that fossil fuels affect human health. Arun SANKAR / AFP/File
Air pollution, such as the extremes seen in India's capital New Delhi, are just one way that fossil fuels affect human health. Arun SANKAR / AFP/File
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Heat, Disease, Air Pollution: How Climate Change Impacts Health

Air pollution, such as the extremes seen in India's capital New Delhi, are just one way that fossil fuels affect human health. Arun SANKAR / AFP/File
Air pollution, such as the extremes seen in India's capital New Delhi, are just one way that fossil fuels affect human health. Arun SANKAR / AFP/File

Growing calls for the world to come to grips with the many ways that global warming affects human health have prompted the first day dedicated to the issue at crunch UN climate talks starting next week.
Extreme heat, air pollution and the increasing spread of deadly infectious diseases are just some of the reasons why the World Health Organization has called climate change the single biggest health threat facing humanity.
Global warming must be limited to the Paris Agreement target of 1.5 degrees Celsius "to avert catastrophic health impacts and prevent millions of climate change-related deaths", according to the WHO.
However, under current national carbon-cutting plans, the world is on track to warm up to 2.9C this century, the UN said this week.
While no one will be completely safe from the effects of climate change, experts expect that most at risk will be children, women, the elderly, migrants and people in less developed countries which have emitted the least planet-warming greenhouse gases.
On December 3, the COP28 negotiations in Dubai will host the first "health day" ever held at the climate negotiations.
- Extreme heat -
This year is widely expected to be the hottest on record. And as the world continues to warm, even more frequent and intense heatwaves are expected to follow.
Heat is believed to have caused more than 70,000 deaths in Europe during summer last year, researchers said this week, revising the previous number up from 62,000.
Worldwide, people were exposed to an average of 86 days of life-threatening temperatures last year, according to the Lancet Countdown report earlier this week.
The number of people over 65 who died from heat rose by 85 percent from 1991-2000 to 2013-2022, it added.
And by 2050, more than five times more people will die from the heat each year under a 2C warming scenario, the Lancet Countdown projected.
More droughts will also drive rising hunger. Under the scenario of 2C warming by the end of the century, 520 million more people will experience moderate or severe food insecurity by 2050.
Meanwhile, other extreme weather events such as storms, floods and fires will continue to threaten the health of people across the world.
Air pollution
Almost 99 percent of the world's population breathes air that exceeds the WHO's guidelines for air pollution.
Outdoor air pollution driven by fossil fuel emissions kills more than four million people every year, according to the WHO.
It increases the risk of respiratory diseases, strokes, heart disease, lung cancer, diabetes and other health problems, posing a threat that has been compared to tobacco.
The damage is caused partly by PM2.5 microparticles, which are mostly from fossil fuels. People breathe these tiny particles into their lungs, where they can then enter the bloodstream.
While spikes in air pollution, such as extremes seen in India's capital New Delhi earlier this month, trigger respiratory problems and allergies, long-term exposure is believed to be even more harmful.
However it is not all bad news.
The Lancet Countdown report found that deaths from air pollution due to fossil fuels have fallen 16 percent since 2005, mostly due to efforts to reduce the impact of coal burning.
Infectious diseases
The changing climate means that mosquitoes, birds and mammals will roam beyond their previous habitats, raising the threat that they could spread infectious diseases with them.
Mosquito-borne diseases that pose a greater risk of spreading due to climate change include dengue, chikungunya, Zika, West Nile virus and malaria.
The transmission potential for dengue alone will increase by 36 percent with 2C warming, the Lancet Countdown report warned.
Storms and floods create stagnant water that are breeding grounds for mosquitoes, and also increase the risk of water-borne diseases such as cholera, typhoid and diarrhea.
Scientists also fear that mammals straying into new areas could share diseases with each other, potentially creating new viruses that could then jump over to humans.
Mental health
Worrying about the present and future of our warming planet has also provoked rising anxiety, depression and even post-traumatic stress -- particularly for people already struggling with these disorders, psychologists have warned.
In the first 10 months of the year, people searched online for the term "climate anxiety" 27 times more than during the same period in 2017, according to data from Google Trends cited by the BBC this week.

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Researchers Document Huge Drop in African Elephants in a Half Century

Elephants walk at the Amboseli National Park in Kajiado County, Kenya, April 4, 2024. REUTERS/Monicah Mwangi/File Photo
Elephants walk at the Amboseli National Park in Kajiado County, Kenya, April 4, 2024. REUTERS/Monicah Mwangi/File Photo
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Researchers Document Huge Drop in African Elephants in a Half Century

Elephants walk at the Amboseli National Park in Kajiado County, Kenya, April 4, 2024. REUTERS/Monicah Mwangi/File Photo
Elephants walk at the Amboseli National Park in Kajiado County, Kenya, April 4, 2024. REUTERS/Monicah Mwangi/File Photo

African elephants are Earth's largest land animals, remarkable mammals that are very intelligent and highly social. They also are in peril. Fresh evidence of this comes in a study that documents alarming population declines at numerous sites across the continent over about a half century.

Researchers unveiled on Monday what they called the most comprehensive assessment of the status of the two African elephant species - the savanna elephant and forest elephant - using data on population surveys conducted at 475 sites in 37 countries from 1964 through 2016.

The savanna elephant populations fell by about 70% on average at the surveyed sites and the forest elephant populations dropped by about 90% on average at the surveyed sites, with poaching and habitat loss the main drivers. All told, there was a 77% population decrease on average at the various surveyed sites, spanning both species, Reuters reported.

Elephants vanished at some sites while their populations increased in other places thanks to conservation efforts.

"A lot of the lost populations won't come back, and many low-density populations face continued pressures. We likely will lose more populations going forward," said George Wittemyer, a Colorado State University professor of wildlife conservation and chair of the scientific board of the conservation group Save the Elephants, who helped lead the study published in the journal Proceedings of the National Academy of Sciences.

Poaching typically involves people killing elephants for their tusks, which are sold illegally on an international black market driven mostly by ivory demand in China and other parts of Asia. Agricultural expansion is the top factor in habitat loss.

The forest elephant population is estimated to be about a third that of savanna elephants. Poaching has affected forest elephants disproportionately and has ravaged populations of both species in northern and eastern Africa.

"We have lost a number of elephant populations across many countries, but the northern Sahel region of Africa - for example in Mali, Chad and Nigeria - has been particularly hard hit. High pressure and limited protection have culminated in populations being extirpated," Wittemyer said.

But in southern Africa, elephant populations rose at 42% of the surveyed sites.

"We have seen real success in a number of places across Africa, but particularly in southern Africa, with strong growth in populations in Botswana, Zimbabwe and Namibia. For populations showing positive trends, we have had active stewardship and management by the governments or outside groups that have taken on a management role," Wittemyer said.

The study did not track a continent-wide population tally because the various surveys employed different methodologies over different time frames to estimate local elephant population density, making a unified head count impossible. Instead, it assessed population trends at each of the surveyed sites.

A population estimate by conservationists conducted separately from this study put the two species combined at between 415,000 and 540,000 elephants as of 2016, the last year of the study period. It remains the most recent comprehensive continent-wide estimate.

"The loss of large mammals is a significant ecological issue for Africa and the planet," said conservation ecologist and study co-author Dave Balfour, a research associate in the Centre for African Conservation Ecology at Nelson Mandela University in South Africa.

The world's third extant elephant species, the slightly smaller Asian elephant, faces its own population crisis, with similar factors at play as in Africa.

Of African elephants, Wittemyer said, "While the trends are not good, it is important to recognize the successes we have had and continue to have. Learning how and where we can be successful in conserving elephants is as important as recognizing the severity of the decline they have experienced."

Wittemyer added of these elephants: "Not only one of the most sentient and intelligent species we share the planet with, but also an incredibly important part of ecosystems in Africa that structures the balance between forest and grasslands, serves as a critical disperser of seeds, and is a species on which a multitude of other species depend on for survival."