Substances that cause DNA mutations are known as mutagens, and mutagens that cause cancers are known as carcinogens. Particular substances have been linked to specific types of cancer. Tobacco smoking is associated with many forms of cancer, and causes 90% of lung cancer.
Human diploid cells have 46 chromosomes and human haploid gametes (egg and sperm) have 23 chromosomes. Retroviruses that contain two copies of their RNA genome in each viral particle are also said to be diploid.
In humans, you would find 23 chromosomes in a sperm cell; 23 chromosomes in an egg cell; and 46 chromosomes in a white blood cell. All human body cells contain 46 chromosomes (two sets of 23 chromosomes). Only the gametes (i.e., the sperm & eggs) contain 23 chromosomes (one set of 23 chromosomes) because two gametes combine to form a new person with 46 chromosomes in his body cells. Body cells grow and reproduce by the process of mitosis.