What key factor should responders assess concerning the effects of a chemical agent?

The key factor that responders should assess concerning the effects of a chemical agent is its toxicity and the route of exposure. Understanding the toxicity of a chemical agent is crucial because it determines the potential harm it could cause to individuals and the environment. Different agents can possess varying levels of lethality or harm depending on their toxic properties. Additionally, knowing the exposure route—whether it's inhalation, ingestion, skin contact, or eye exposure—enables responders to develop appropriate safety measures and treatment protocols. This knowledge is essential for ensuring the safety of responders and the public while effectively mitigating the chemical threat.

The other factors listed, while they may hold some relevance in a broader context, do not provide the critical information necessary for immediate response and protection. The color and odor of an agent may offer some initial cues but do not give a complete understanding of potential health effects. Information about the origin and manufacturing date might be useful in certain investigations or historical contexts, but it does not address immediate health risks. Furthermore, cost and availability are not relevant to the assessment of effects, as they do not impact how a chemical agent interacts with human physiology.