Carcinogens are substances that can lead to cancer by causing changes in the DNA of cells. These changes can disrupt normal cell growth and division, leading to uncontrolled cell growth, which is a hallmark of cancer. Common carcinogens include certain chemicals, such as those found in tobacco smoke, as well as radiation and some viruses like human papillomavirus (HPV). Not all carcinogens are equally dangerous; some may only pose a risk with prolonged exposure or at high doses. It's important to be aware of these substances in our environment, such as in certain foods or industrial settings, to reduce the risk of developing cancer over time.