12. explain why most studies conducted in the field of environmental epidemiology are nonexperimental.

Most studies conducted in the field of environmental epidemiology are nonexperimental because it is unethical.

Explanation:

Environmental epidemiology focuses on small groups of people considered to be at risk because they already have the diseased being investigated. It is unethical to expose people to potentially dangerous environmental agents only for an epidemiological study. This is why most of these studies are nonexperimental.

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answer; the nazca plate is converging with the south american plate