Should Carbon Dioxide be Considered as a Form of Air Pollution?

Carbon dioxide was first declared as an air pollutant by the Environmental Protection Agency in 2009. It sparked lots of debate on whether a natural occurring gas should be even considered as an air pollutant. We commonly associate carbon dioxide with global warming and for causing climate change.  

Ocean Acidification
Source: Oceana
http://usa.oceana.org/what-ocean-acidification

However, there are many people who are largely unaware of ocean acidification, which is often labelled as the other carbon dioxide problem. Oceans serve as major carbon sinks as they can absorb the carbon dioxide from the atmosphere and it is estimated that about one third of the anthropogenic carbon emissions is absorbed by the oceans, representing 22 million tons a day. When carbon dioxide dissolve in the water, carbonic acid will be produced which increases the acidity of the ocean, giving rise to the "ocean acidification" terminology. The ocean pH has been dropped by 0.1 over the past two centuries, which may seem minimal. However, this constitutes up to a 30 percent increase in acidity as the pH level is on a logarithm scale. For example, pH 7 will be ten times more acidic than pH 8.

This increase in acidity can destroy the delicate marine biodiversity in the oceans by lowering the amount of free carbonate ions that shell-producing marine organisms require for growth. Below is a good illustration by Oceana USA which explains the ocean acidification process.

Therefore, ocean acidification has the potential to inflict great harm to our vulnerable marine ecosystems, which we depend for marine food. Perhaps it is thus justifiable to label carbon dioxide as a major air pollutant. On the other hand, skeptics will point out that fluctuations in carbon dioxide concentration have occur in the past as well due to natural causes such as volcanic eruptions that can emit huge amount of carbon dioxide gas. Based on reconstruction of past records of atmospheric composition from the extraction of ice cores, it has been found out that concentration of carbon dioxide was even 20 times higher 500 million years ago compared to the present values.

However, it is irrefutable that human emissions have significant rose since the Industrial Revolution and we are responsible in speeding up the natural increase in carbon dioxide concentrations through human activities. Although carbon dioxide is a natural occurring gas in our atmosphere, it is the dose that makes the poison. The current marine ecosystem will be severely impaired at the current rate of carbon emissions.

Feel free to share your opinions on whether carbon dioxide should be considered as an air pollutant! :)