Final answer:
Regular exposure to loud noises is the primary environmental cause of hearing impairment in later life.
Step-by-step explanation:
The primary environmental cause of hearing impairment in later life is regular exposure to loud noises.
Repeated exposure to loud sounds can damage the delicate hair cells lining the cochlea, which are responsible for transmitting sound signals to the brain. Once these hair cells are damaged or destroyed, they do not regenerate, resulting in permanent hearing loss.