This week, the Environmental Protection Agency (EPA) will hold a public hearing about its remediation plan for cleaning up chemicals in and around East Palestine, Ohio. It follows the derailment of a Norfolk Southern train carrying hazardous chemicals like vinyl chloride and butyl acrylate near the town earlier this month. Residents were temporarily evacuated from the area two days later to allow for a controlled burn of the chemicals. EPA health officials have been monitoring the air and water in the area and testing for chemicals as part of their human health risk assessment. We wanted to know: What goes into an assessment like that? And how does the EPA know if people are safe — now and long-term? To walk us through that assessment, we talked to Karen Dannemiller, an associate professor of environmental health science at The Ohio State University.