Answer the following question given this paragraph: 

Does everyone who smokes develop lung cancer? No, of course not. Is it possible to get lung cancer without smoking? Sadly, yes it is. That's not to say there is no relationship between the two: smoking is still the leading cause of lung cancer. But it does suggest that a person's genetic background has a role in this process. Apart form true single gene disorders, environmental factors, or environmental triggers , may determine the development of disease in individuals genetically predisposed to a particular condition. Environmental triggers may include stress, physical and mental abuse, diet, exposure to toxins, pathogens, and radiation. Many cancers are thought to have an environmental component. It has been suggested that environmental factors play a role in autism as well. Asthma is obviously triggered under certain environmental conditions.


Q: Many cancers, as well as autism, are thought to have what component, which is certainly a factor in asthma?


A:
environmental