What are xenobiotic chemicals and what is their environmental significance?

Xenobiotic chemicals are man-made. However, all chemicals that enter the environment pose a risk to the exposed ecosystem. Are xenobiotic chemicals more dangerous than other chemicals?

Chemicals can be broken down in one of three ways: Either it can be mineralized or completely metabolized to water and carbon dioxide; a chemical can be partially broken down via biodegradation, or it can be cometabolized. What are the differences between these breakdown paths?

What are some factors that affect toxicity levels? Explain why these factors would influence toxicity levels in living organisms