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Carbon Dioxide

What is carbon dioxide?

Carbon dioxide (CO2) is a colourless, odourless gas formed from carbon and oxygen atoms. It is a natural part of the Earth’s carbon cycle: the circulation of carbon between the atmosphere, plants, animals, soils and oceans. Humans exhale CO2 and plants absorb it. However, human activity since the industrial era has significantly increased levels of CO2 and altered this cycle, decreasing the ability of natural carbon sinks such as forests to remove it from the atmosphere. Carbon dioxide is now best known as the primary greenhouse gas emitted through human activity.

Where does it come from?

Carbon dioxide is primarily produced through burning fossil fuels such as oil, coal and natural gas. Some main sources of emissions globally include transport, industry, and fuel burning for electricity and heating. It is also produced through natural sources such as animals, volcano, oceans, soils, and plants.

How does it affect our health?

Carbon dioxide can build up indoors if rooms are not well ventilated. High CO2 concentrations indoors can make people feel lethargic, cause headaches and difficulty concentrating, dizziness and even nausea. Higher concentrations (e.g. >5000ppm over a few hours) can provoke increased heart rate, elevated blood pressure, or even in extreme cases coma, asphyxia, and convulsions.

Indirect health effects can also be drawn from CO2’s contribution to climate change, which is predicted to negatively impact air quality and may thus aggravate the adverse health effects associated with increased pollutants (such as ozone and particle pollution).

Environmental effects?

As the primary greenhouse gas contributing to global warming and climate change, CO2 bears significant environmental impacts. CO2 is a ‘heat-trapping’ gas, in that it limits the heat radiation that reaches the Earth from being reflected back away again. CO2 and other greenhouse gases thus contribute to the “greenhouse effect”, trapping more and more heat in the Earth’s atmosphere instead of the heat being reflected away.

Increasing global temperatures can have dire consequences for our planet and environment. Rising sea levels, increased likelihood of droughts and wildfires, species loss and ecosystem damage are just a few consequences.

Awareness of these dramatic, negative environmental effects of increased carbon emissions have led to a global effort to try to reduce these. In many cases, reducing the sources of carbon emissions (e.g. fossil fuel combustion) will also help reduce levels of ambient air pollution, as they are often produced from the same sources. However this is not always the case.

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