What kind of incidents does the National Response Center primarily handle?

The National Response Center (NRC) is specifically designed to coordinate responses to incidents involving the release of oil or hazardous substances into the environment. This includes a variety of situations such as chemical spills, oil leaks, and other environmental emergencies that may pose a threat to public health or the ecosystem. The NRC serves as a central point for reporting incidents that require federal response capabilities, ensuring that the appropriate resources and agencies are mobilized quickly to manage these hazardous situations.

In contrast, the other options do not fall under the NRC's mandate. Employment disputes concern labor relations and are managed through different legal and organizational frameworks. Environmental assessments are typically conducted by agencies for regulatory compliance and do not involve immediate response measures. Transportation safety checks pertain to the regulation and oversight of transportation systems, ensuring safe practices but do not specifically address the management of environmental incidents related to hazardous substances. Thus, the focus of the NRC is distinct and specifically geared towards handling incidents related to oil and hazardous substance spills.