What is the primary focus of toxicology?

The primary focus of toxicology is the study of the adverse effects of chemicals on living organisms. This field emphasizes understanding how various substances can cause harm, their mechanisms of action, dosage-response relationships, and the biological effects they produce. Toxicologists evaluate the toxicity of chemicals, including pharmaceuticals, pollutants, and industrial chemicals, to ensure safety and mitigate risks to human health and the environment.

In the context of the other options, the study of chemical reactions generally pertains to broader chemistry fields rather than specifically focusing on toxic effects. Similarly, while the positive effects of herbs might be a part of ethnobotany or pharmacognosy, toxicology is concerned with harmful effects rather than beneficial ones alone. Finally, environmental impact assessments are related to evaluating the potential effects of projects or actions on the environment but do not specifically focus on toxicological outcomes. Thus, the correct answer aligns with the core objectives of toxicology as a field dedicated to understanding harmful interactions between chemicals and biological systems.