The question is about who should be contacted immediately if someone accidentally consumes or comes in contact with a potentially toxic substance.
Step 2: Evaluate the Options
National Chemical Toxicity Center
National Poison Control Center
American Poison Chemical Society
American Toxic Chemical Center
Step 3: Determine the Most Appropriate Option
The most appropriate organization to contact in the event of exposure to a toxic substance is the National Poison Control Center, as they specialize in providing immediate assistance and information regarding poisonings.