The branch of science that deals with the study of chemicals and their adverse effects on living organisms and the environment is called:

The branch of science focused on the study of chemicals and their adverse effects on living organisms and the environment is known as toxicology. This field investigates how various substances can cause harm, the mechanisms of toxicity, and the dose-response relationship, essentially examining the impact of chemicals on health and ecosystem safety.

Toxicology encompasses both the biological effects of toxic substances and their environmental implications, making it crucial for understanding the risks associated with chemical exposure. This discipline helps in assessing hazards, establishing safety standards, and developing preventative measures to protect public health and the environment.

While chemistry studies the properties and reactions of substances, it does not specifically focus on the harmful effects. Similarly, biology examines living organisms and their interactions but does not focus exclusively on chemicals or toxic effects. Environmental science integrates information from various fields to address environmental issues but is broader and does not exclusively concentrate on toxins and their effects. Thus, toxicology is the most precise field related to the question posed.