Which Energy Source Is The Most Harmful, & Which Is Safest?

Below, we outline which energy sources might be the most harmful to humans, and which might be the safest.

We’ve compared the different energy sources across several measures of harm/safety to get a better idea of this.


Summary – Which Energy Sources Are The Most Harmful, & The Safest?

Ways To Measure Harm & Safety For Energy Sources

In the context of this guide, we are mainly referring to human health and safety

There’s more direct forms of harm, like direct injuries and deaths from accidents at workplaces.

And, there’s more indirect forms of harm to health or everyday living, from air pollution, and emissions which can contribute to a changing climate

We provide a broader assessment of the different energy sources on other aspects of society in another guide


Which Energy Sources Are The Most Harmful?

– Workplace Accidents & Air Pollution

Brown coal, and also black coal appear to be the most dangerous/harmful forms of energy when measuring by workplace accidents and air pollution

Oil might be in second

Interestingly, bioenergy is third according to some data

Of the three main fossil fuels, natural gas may be less harmful than coal and oil


– Greenhouse Gas Emissions

Fossil fuels tend to be the highest emitters – coal, oil, and natural gas – in that general order

Although, some types of biomass may be one of the higher emitters of all energy sources too


Which Energy Sources Are The Safest?

– Workplace Accidents & Air Pollution

Nuclear energy appears to be safest form of energy according to several metrics, followed by renewables like solar and wind

Neither nuclear nor renewables like solar or wind release air pollutants during energy generation


– Greenhouse Gas Emissions

Along with renewables like solar, wind, and also hydro, nuclear energy might emit the least emissions over the lifecycle of an energy source


Rate Of Harm vs Total Harm

It’s important to look at the per unit output of each energy source.

An energy source like coal might be overrepresented in some results because coal is used in much greater energy shares across the world right now than other energy sources i.e. more total coal is used than other energy sources.

So, expressing different results in terms of the per unit of power they output might provide more of a ‘like for like’ comparison between energy sources.


Safety & Harm Might Differ From Place To Place, & Change Over Time

Metrics like air pollution might differ between individual power plants using different levels of air pollutant and carbon capture technology.

Therefore, the potential impact on humans from different energy sources might vary from place to place.

Additionally, the use of new safety practices and processes, or new technology might reduce the harm from different energy sources in the future. So, the potential for harm might reduce over time too.


An Asterisk On Harm For Some Energy Sources

Fossil fuels like coal may have the potential to cause harm in some ways, but, fossil fuels still play a very important part in society, and fossil fuels also have a range of benefits that may contribute to them being one of the best energy sources for some applications


An Asterisk On Harm Attributable Specifically To Air Pollution

Some reports may also question how much harm exactly is attributable to air pollution from fossil fuels like coal.

Some argue that it’s too difficult to a) link air pollution and health conditions or mortality, and b) separate pre existing conditions and the impact of air pollution caused by coal power plants, or even smog from vehicles.

In addition, some reports even claim that pollution from fossil fuels is overstated or over exaggerated in some cities and regions.

We outline air pollution and the potential effects in greater detail in another guide


An Asterisk On A Changing Climate, & What Can Reliably Be Attributed To Different Energy Sources

A similar point might be made about emissions, a changing climate, and exactly how attributable certain effects of a changing climate are to different energy sources


From ourworldindata.org:

[Examples of effects of climate change that might impact humans might include] … extreme weather, sea level rise, reduced freshwater resources, crop yields, [and] heatstroke …

[But, there might be uncertainty in determining the impact of climate related events on humans]

It’s particularly challenging to predict how many climate change related deaths we might experience decades from now, and how much we could attribute to a specific energy source.

This makes it difficult to compare specific figures related to long-term deaths.


Workplace Accidents & Air Pollution From Different Energy Sources

Total Deaths – Per 1000 TWh Generated

On a per 1000 TWh basis, it appears that coal is responsible for the most total deaths

Oil is in second

Fossil fuels make up the top three energy sources


visualcapitalist.com indicates that the total deaths of each energy sources per 1000 TWh (tera watt hours) generated are:

[Coal leads by a significant margin, at 100,000 deaths per 1000 TWh produced]

[Oil is second at 36,000]

[Gas is third at 4000, followed by Hydro at 1400 (skewed by Banqiao dam collapse), Solar (rooftop solar only) at 440, Wind at 150, and Nuclear – 90 (includes nuclear power plant incidents like Chernobyl and Fukushima)]


Short Term Deaths From Accidents & Air Pollution – Per TWh Generated

On a per TWh basis, brown coal is responsible for the most deaths from accidents and air pollution in the short term

Black coal is in second, with oil third

So, fossil fuels make up the leading energy sources again here


ourworldindata.org indicates that the rate of short-term deaths from accidents and air pollution related to energy production, standardised to the deaths resultant from the production of one terawatt-hour (TWh) of energy (one terawatt-hour is roughly equivalent to the annual energy consumption of 12,400 US citizens according to ourworldindata.org) are:

[Brown Coal leads at 32.72 deaths per terawatt hour produced]

[Coal is in second at 24.62]

[Oil is third at 18.43]

[Following that is Biomass at 4.63, Gas at 2.82, and Nuclear at 0.07]


Our paraphrased notes from that same ourworldindata.org report are that:

Air-pollution related deaths account for greater than 99% of brown coal, coal, oil and gas related deaths, 70% of nuclear-related deaths, and all biomass-related deaths

Cancer from radioactive exposure is taken into account in the above data


Total Number Of Deaths If All Global Energy Production Was Met Through One Energy Source

Again, brown coal comes in at the top

This is followed by black coal, and then oil


ourworldindata.org indicates that, hypothetically, if all energy production in the world was met through one energy source in 2014, the number of deaths from each energy source might have been:

[The most deaths come from Brown Coal at 5.3 million deaths]

[Coal is second at 3.91 million]

[Oil is third at 2.93 million]

[This is followed by Biomass at 736,170, Gas at 448,539, and Nuclear at 11,776]


Deaths In General

Several reports indicate that coal is the ‘most dangerous’ or the ‘most harmful’ energy sources, particularly when it comes to which energy sources produce the most air pollution


From theguardian.com:

In terms of raw numbers of deaths, coal is the most dangerous source of energy for workers

In terms of deaths by energy output, coal is probably the most dangerous

[Coal may be responsible for thousands of workers’ deaths each year between a combination of poorly regulated mining practices, inherent danger and bronchus invading dust]


In a separate guide about air pollution, we list the combustion of fossil fuels like coal as a main source of air pollutants, and, air pollution in linked to a range of health conditions and also mortality rates


Greenhouse Gas Emissions From Different Energy Sources

Total Annual Emissions

Coal leads global annual emissions

Liquid oil is second, with natural gas in third


From ourworldindata.org, global annual per year CO2 emissions by fuel source, measured in billions of tonnes per year, in 2013, were:

[Solid Fuel (Coal) in first at 15.15 (Bt)]

[Liquid (Oil) in second at 11.79]

[Gas (Natural Gas) in third at 6.62]

[Cement Production was fourth at 2.03, followed by Gas Flaring at 249.36 (Millions of tonnes)]


Each country differs with the energy sources that emit the most greenhouse gases though.

Additionally, different sectors also have different dominant gases that are emitted.


kg of CO2 Emissions per Mega Watt Hour Of Electricity Produced

Coal leads kg of CO2 emissions per megawatt hour of electricity produced

Oil is in second, with natural gas in third


From ourworldindata.org, carbon dioxide emissions in kg of CO2 produced per mega watt hour, are:

[Charcoal is first at 403.2 kg CO2]

[Coke is equal second at 385.2 kg CO2, along with Oil Shale and Tar Sands at 385.2 kg CO2]

[Peat is third at 381.6 kg CO2[

[Followed by Lignite at 363.6 kg CO2, Anthracite at 353.88 kg CO2, Sub Bituminous Coal at 345.96 kg CO2, Bitumen at 290.52 kg CO2, Diesel Oil at 266.76 kg CO2, Crude Oil at 263.88 kg CO2, Shale Oil at 263.88 kg CO2, Aviation Gasoline at 252 kg CO2, Jet Gasoline at 252 kg CO2, Motor Gasoline at 249.48 kg CO2, and Natural Gas at 201.96 kg CO2]


Emissions Equivalent Over Lifecycle Of Energy Source

The lifecycle of the energy source includes the different stages, from manufacture, to construction, to operation, to decommissioning and waste, and so on

Coal leads CO2 equivalent emissions per kWh supplied

Some types of biomass are second, with gas in third


From wikipedia.org, the Lifecycle CO2 equivalent (including albedo effect) from selected electricity supply technologies .. arranged by gCO2eq per kWh (CO2 equivalent per kilowatt hour of electricity supplied) in median values … are:

[Coal is first at 820 median gCO2eq per kWh]

[Biomass (co-firing with coal) is second at 740]

[Gas (combined cycle) is third at 490]

[Followed by Biomass (dedicated) at 230, Solar PV (utility scale) at 48, Solar PV (rooftop) at 41, Geothermal at 38, Concentrated Solar Power at 27, Hydropower at 24, Wind Offshore at 12, Nuclear at 12, Wind Onshore at 11]


It’s unclear whether the above data takes into account leakage of method during raw natural gas extraction.

Also, it appears as though oil has been omitted from the above data.


You can also check out this guide to view more information on the lifecycle carbon footprint of different energy production sources


Direct Harm vs Indirect Harm

– Direct Harm

May include things such as injuries and deaths in the workplace

This could happen at mine sites, during manufacturing, at power plants, and so on

Examples might include mining accidents, nuclear explosions, dam collapses for hydroelectricity, exposure to toxic or radioactive material and substances (such as nuclear waste, or waste from coal power plants, 


– Indirect Harm

May include exposure to air pollutants in the air (impacting air quality), other types of pollution and waste pollution, and, experiencing the impact that emissions may have on the climate, and so on


Factors To Consider When Assessing Safety Of Each Energy Source

Potential factors might include:


– How safe is the energy source overall?

What totals for, and also the rate of workplace accidents that lead to injury or death (mortality rates)?


– How does the energy source contribute to a negative impact on human health or human well being?

Air pollution, and emissions contributing to a changing climate are two ways human health and well being might be impacted


Is there any risk of exposure to hazardous waste, or radiation?

Nuclear waste for example may be of different radioactivity levels (and therefore be a potential risk for different lengths of time

If nuclear/radioactive waste is managed correctly, it might pose minimal risk to humans


Are there any toxicity risks?


Is there any risk of explosion or flammability at any stage?


– What are both the short term and long term risks and impacts of the energy source?

Short term risks and impact happen directly

Longer term risks and impact may happen indirectly over years or decades (spanning multiple generations)




1. https://www.visualcapitalist.com/worlds-safest-source-energy/

2. https://ourworldindata.org/what-is-the-safest-form-of-energy

3. https://www.theguardian.com/environment/2014/may/15/most-dangerous-form-of-energy-coal

4. Various ‘Better Meets Reality’ guides

5. https://ourworldindata.org/fossil-fuels

6. https://en.wikipedia.org/wiki/Life-cycle_greenhouse-gas_emissions_of_energy_sources

7. Hannah Ritchie & Max Roser (2019) – “Energy Production & Changing Energy Sources”. Published online in OurWorldInData.org. Retrieved from https://ourworldindata.org/energy-production-and-changing-energy-sources#introduction 

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