Hazardous substances can be broadly categorized into several types: carcinogens, mutagens, teratogens, irritants, corrosives, and sensitizers. Carcinogens are known to cause cancer, while mutagens can cause genetic mutations. Teratogens can lead to developmental abnormalities in fetuses. Irritants and corrosives can cause damage to skin and mucous membranes, and sensitizers can cause allergic reactions.