Human Health: Treating Causes, not Symptoms

19 minute read

Updated on Mon Mar 29 2021

Solving the climate crisis may be one of the most important health opportunities of the 21st century! In this chapter we look at how health and climate change are linked and why this is important.

Indoor air pollution and health

What percentage of the world’s population do you think cooks by directly burning wood, charcoal, animal dung or coal?

The smoke and soot produced when cooking with these fuels indoors can cause heart and lung diseases, as well as cancers and strokes. Because of these diseases, indoor air pollution is responsible for 4.3 million early deaths every year, mostly in developing countries, as shown below.

Share of deaths from indoor air pollution, 2017

These traditional cooking methods also contribute 2-5% of global yearly greenhouse gas emissions, both through burning the fuels themselves and from the activities required to gather them.

Impacts of traditional cooking methods

But it’s not only the amount of emissions produced from traditional cooking practices that cause problems. The types of pollution produced are problematic for both the climate and our health too. Open fires and inefficient stoves often have poor air-circulation around them, leading to the production of “black carbon” (a major component of soot).

So, how much of a problem is black carbon for the environment?

Black carbon

Even though there is less black carbon in the atmosphere than CO₂, it is currently the second biggest contributor to global warming because it absorbs so much heat. However, unlike CO₂, black carbon is quickly removed from the atmosphere by rain. While CO₂ continues to cause warming for hundreds of years after it has been emitted, the contribution of black carbon to global warming would end quickly if we stopped producing it.

This makes solutions that reduce black carbon emissions particularly promising: if all black carbon emissions stopped, the effects would be seen within only a matter of decades!

What would happen if we stopped emitting black carbon tomorrow?

Improved cookstoves (either solar-powered or fuel-burning) can cut emissions by as much as 95% as well as saving lives. By reducing black carbon and other pollutants, it is estimated that 150 million clean cookstoves could help avoid 2.2 million early deaths in India.

There are even more benefits! Improved cookstoves use less fuel, which reduces the time people spend gathering firewood. This is a physically demanding and often dangerous task, especially for unaccompanied women.

Outdoor air pollution due to transport

Stopping indoor air pollution is only half of the story. Transport is a major source of outdoor air pollution and contributed 16% of the global greenhouse gas emissions in 2014. It is also estimated that emissions from transport contributed to 385,000 early deaths in 2015.

Outdoor air pollution

Swapping to electric cars is one possible solution, as they produce less pollution on the road. However, they don’t solve other problems caused by cars, such as traffic accidents. They also only reduce emissions if renewable energy is used to produce the electricity.

By contrast, taking public transport (such as buses, trams and trains) reduces pollution per passenger as well as traffic. This is especially the case if the vehicles are full of passengers and are run on clean fuels or electricity.

Even better are active forms of transport, such as walking and cycling. These have the biggest positive impact on both health and solving climate change.

Transport solutions to climate change and health problems

Walking and cycling reduce emissions, improve local air quality, and help prevent diseases related to inactive lifestyles.

Governments can encourage people to walk and cycle more through cost-effective strategies, such as improving pavements and cycleways.

Why should we link health and climate change?

The World Health Organisation estimates that air pollution causes as many as one in eight deaths, as well as contributing to climate change.

Deaths due to air pollution

Politicians tend to avoid strong climate change policies due to their perceived costs, and because the climate benefits to their country are only felt if many other countries do the same.

On the other hand, the health benefits of reducing air pollution from cars and cookstoves are felt quickly and by the people in that country.

Therefore, thinking about the immediate health benefits of reducing air pollution may help persuade politicians to take action on emissions. These policies aim to improve public health, but they also tackle climate change. Win-win!

Win-win: Climate change & Health

Meeting the targets of the 2016 Paris Agreement on climate change would save over one million lives a year from air pollution by 2050. Also, these policies would more than pay for themselves in gains from improved health, such as increased productivity of healthy workers and reduced spending on healthcare.

For every $1 spent on policies to achieve the targets of the Paris Agreement, how many dollars would be gained in health benefits?

Conserving nature for our health

Thinking about both the climate and human health could also persuade politicians to reduce deforestation.

Cutting down trees not only results in carbon emissions, but can also lead to more disease outbreaks. How? 75% of new infectious diseases in humans come from animals. These are called “zoonoses”.

Zoonoses are diseases that pass from animals to humans

When forests are cut down, and roads built within them, humans come into much closer contact with the animals that live there. This means that diseases are more likely to spread between people and animals.

Deforestation brings people into close contact with animals, increasing the chance of diseases spreading

In the recent past, human impacts on the natural world have been linked to a number of viral epidemics and pandemics. These include COVID-19 (2019-ongoing), Zika (2015-19) and SARS (2002-04). Outbreaks of Ebola and Malaria have also been linked to deforestation.

Preventing the loss of forests could reduce the chance of future disease outbreaks at the same time as limiting carbon emissions.

And that’s not the only health reason for conserving nature. A growing body of evidence suggests that experiencing nature can have great benefits for our physical and mental wellbeing. Put simply, being around plants and animals makes us happy!

In one study, it was found that patients who could see green areas from their hospital windows recovered from their surgery faster and used fewer painkillers than similar patients that had no such views!

Diet and Health

What we eat impacts not only our health, but the health of the planet.

We currently produce enough food to feed our global population, but this is not shared equally. 11% of the global population is undernourished, which means they don’t have enough food to support a normal, healthy life. At the same time, 8% of global deaths were due to obesity in 2017.

What causes obesity?

Eating too much meat (particularly red and processed meats), processed food, and sugary drinks increases the likelihood of obesity, as well as type 2 diabetes and some cancers.

This diet is also extremely bad for the environment! Far more emissions are released when meat is produced than plant-based foods because energy is lost higher up the food chain. What’s more, animals like cows and sheep are the greatest contributors to global emissions of methane, a greenhouse gas that is even more powerful than CO₂. The environmental impacts of eating meat are covered in more detail in the Food and Farming course.

There are internationally agreed guidelines on healthy eating. These recommendations only consider the health outcomes of diets, and advise eating more plant-based food and less meat and sugar. This diet is much better for the environment!

If people followed these existing guidelines, greenhouse gas emissions from our diet would decrease by 29%.

The latest research suggests that these guidelines should now be updated to recommend even less processed food and meat. To find out more about food and the environment, check out our 'Food and Farming' course!

If everyone ate the healthiest diet…


Healthier diets, clean cookstoves and transport choices are just three of the ways we can improve global health and slow climate change at the same time. Understanding and making the most of these links may motivate politicians to take rapid and effective action on the climate crisis.

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