Should carbon dioxide (CO2), a naturally occurring greenhouse gas that is essential to life, be placed in the same league and treated as other toxic pollutants? I believe the answer is no, but the U.S. Supreme Court has ruled otherwise.
In 2007, the court ruled that CO2 and other greenhouse gases must be regulated under the Environmental Protection Agency’s (EPA) Clean Air Act as pollutants; after studying the issue, the EPA recently issued a regulatory response in line with the Supreme Court decision. This means that CO2 should be included in the same category as the other six “criteria” pollutants that the United States currently regulates: lead, sulfur dioxide, nitrogen oxides, particulate matter, carbon monoxide and ozone. But can this categorization be right?
According to the Supreme Court, CO2 and other greenhouse gases such as methane and HFCs are harmful to the public not because they cause respiratory issues or are carcinogenic, but because they cause climate change. However, CO2 — although understood as dangerous in high concentrations — is a natural part of the Earth’s climate system and has varied in concentration naturally for millions of years. As a greenhouse gas, this compound serves an important role in regulating and maintaining the Earth’s temperature. Greenhouse gases on the whole help to keep the temperature at a level that can support human and other life.
Putting this particular molecule in the same group as the other pollutants is a slippery slope. For example, water vapor is also a greenhouse gas. It is emitted from the internal combustion engines found in automobiles and from power plants. Water vapor also drives the planet’s weather patterns and temperature in a ways similar to CO2; many climate scientists would argue that water vapor has an even greater effect on climate change than C02. Yet water vapor is not included with the other greenhouse gases mentioned in EPA regulations recently proposed in response to the 2007 Supreme Court decision. In fact, it is not discussed at all.
Scientists are not even certain when the effects of high concentrations of these gases will cause direct and widespread harm to human health. On the other hand, ozone, a criteria pollutant, can and does cause harm daily. Greenhouse gas “pollutants” are different in this aspect, as well.
The EPA’s recent regulatory response to the Supreme Court ruling is based on three findings: First, the Clean Air Act’s broad definition of a “pollutant” necessarily includes greenhouse gases such as CO2, hydrofluorocarbons (HFCs), and methane. Second, current and future concentrations of greenhouse gases, as they mix with the atmosphere, endanger public health and well-being. Third, motor vehicles emit greenhouse gases and also endanger public health. However, questions remain as to how the EPA will actually regulate these kinds of “pollutants” and how to gauge their “endangerment” to public health. Certainly, C02 cannot be regulated in the same way as other “criteria” pollutants because it’s naturally occurring and necessary for life on the planet.
Clearly, the EPA needs to find another approach to both group and regulate emissions of this kind.
Cassie Lopez is a Rice University senior majoring in environmental engineering sciences, and a student of Kirstin Matthews, Baker Institute fellow in science and technology policy. Next fall, Lopez plans to enroll in the professional science master’s environmental analysis and decision-making track at Rice University’s School of Natural Sciences.