Which of the following is a potential issue of VOCs?

Volatile Organic Compounds (VOCs) are chemical compounds that easily vaporize at room temperature and can significantly impact both indoor and outdoor air quality. The correct answer reflects the role of VOCs in environmental issues such as urban smog and global warming. When released into the atmosphere, VOCs can react with nitrogen oxides, especially in the presence of sunlight, leading to the formation of ground-level ozone, a key component of smog. This not only affects air quality but can also contribute to broader global warming concerns, as some VOCs are potent greenhouse gases.

Other options do not accurately represent the nature of VOCs. For instance, VOCs do not improve indoor air quality; instead, they can lead to health issues such as headaches, dizziness, or respiratory problems when present in high concentrations indoors. Furthermore, they are not entirely safe for human health, as many VOCs are associated with negative health effects. Lastly, while energy efficiency is an important consideration in building and design, VOCs do not inherently enhance this aspect; rather, products low in VOCs are often preferred to create better indoor environments.