A local manufacturing plant reports a spill that released pollutant A into the local watershed. Pollutant A is a toxic substance. Local officials must determine if the residents should be evacuated from the area. Initial groundwater samples show pollutant levels at 5 mg/kg of water. Which decision is supported by the empirical evidence provided by the dose-response curve? Evacuation is not needed; continue groundwater monitoring. Residents should be evacuated until levels decrease. The spill no longer needs to be monitored. Residents should only evacuate above LD50.