Which term describes exposure that is constant and always present in the environment?

• A. Single Exposure
• B. Vertical Transfer
• C. Case
• D. Continuous Exposure

Answer: (D)

Exposure that is constant and always present in the environment is described as continuous exposure. This means a person is continually subjected to the agent over time, leading to a steady or cumulative dose. For example, living in a home with a persistent source of radon or with ongoing high levels of environmental pollution results in continuous exposure.

This differs from a single exposure, which is a one-time contact with the agent, and from vertical transfer, which refers to transmission from mother to child as a pathway rather than a duration of exposure. A case is simply an individual who has the disease, not the pattern of exposure.