Final answer:
Tar is the most damaging carcinogenic substance in tobacco smoke to the lungs, as it binds to DNA and can cause mutations that may lead to lung cancer. It also contributes to the development of COPD due to a reduction in alveolar elasticity.
Step-by-step explanation:
Of the carcinogenic substances in tobacco smoke, the most damaging to the lungs is tar. Tar contains several cancer-causing chemicals that can bind to DNA and promote cell mutations, which may lead to lung cancer. In tobacco smoke, other potent carcinogens include benzopyrene, acrolein, and nitrosamines; however, tar is particularly harmful because it accumulates in the lungs and can deeply penetrate lung tissue. Moreover, exposure to compounds like carbon monoxide and cyanide in cigarette smoke reduces alveolar elasticity, contributing to chronic obstructive pulmonary disease (COPD), a serious lung condition.