Which environmental issue is regulated by the EPA?

The regulation of environmental issues by the Environmental Protection Agency (EPA) involves various concerns aimed at protecting air, water, and land from pollutants. Among the options provided, carbon emissions are a significant area addressed by the EPA, particularly because of their impact on climate change.

Mold, while it can have serious health implications, is not directly regulated by the EPA in the same manner as other pollutants. Instead, the EPA provides guidelines and recommendations for mold remediation and prevention, but it does not set enforceable standards specific to mold levels in homes or buildings. Thus, it isn't a focus of EPA regulation like carbon emissions, which are controlled under laws such as the Clean Air Act, where the agency has specific authority to regulate emissions from various sources.

Plastic disposal and waste recycling are also significant environmental issues; however, these areas are primarily managed at the state and local levels, with various regulations that may intersect with EPA guidelines, but again, they do not fall under direct EPA regulation like carbon emissions do.

Therefore, carbon emissions is the appropriate answer relating to direct regulation by the EPA, highlighting the agency's role in addressing significant pollutants to protect public health and the environment.