Principles and Practice of Engineering (PE) Environmental Practice Exam

Chlorofluorocarbons (CFCs) primarily cause ozone layer depletion due to their chemical characteristics. When CFCs are released into the atmosphere, they eventually rise up to the stratosphere, where ultraviolet (UV) radiation causes them to break down and release chlorine atoms. These chlorine atoms are highly reactive and can destroy ozone molecules (O3) in a catalytic cycle. A single chlorine atom can destroy thousands of ozone molecules before it is removed from the stratosphere. The depletion of the ozone layer is particularly concerning because it protects life on Earth from harmful UV radiation, which can lead to increased skin cancer rates, eye cataracts, and other environmental effects.

The other choices do not accurately reflect the primary environmental effect of CFCs. While CFCs have some potential to act as greenhouse gases and contribute to global warming, their most significant and well-documented impact is on the ozone layer. Acid rain generation is typically associated with sulfur dioxide and nitrogen oxides, not CFCs. Thus, the correct answer aligns precisely with the most critical environmental impact attributable to CFCs.