Final answer:
Alpha particles can be stopped by thin shielding but are dangerous when ingested or inhaled, as they can damage DNA and cause cancer.
Step-by-step explanation:
Alpha particles can be stopped by very thin shielding but have much stronger ionizing potential than other types of radiation. When alpha particles are ingested or inhaled, there is no protective skin covering the cells, making it possible to damage the DNA and cause cancer. In a situation where radioactive emitters are spread in the environment, inhalation or ingestion of alpha emitters can pose a serious threat as they have the ability to penetrate living tissue.