In 2018, a research group is interested in studying the relationship between exposure to a particular chemical and reproductive disorders. They identify a group of people who were exposed to contaminated drinking water during an incident in 1985 and another group who were never exposed. Then they examine medical records to see if those in the exposed group were more likely to develop reproductive disorders over the 30 years following their exposure. This is what type of study?

Epidemiological Study

Explanation:

An epidemiological study is a study that examines the degree to which an exposed population or sample prone to illness or death compared to the degree to which a similar unexposed population or sample are prone to illness or death. This is done by considering sex, social status, age and race of the population.

Since the research group in 2018 identify a group of people who were exposed to contaminated drinking water during an incident in 1985 and another group who were never exposed in their study, it their type of study is an epidemiological study.

Epidemiological Study

Explanation:

This type of study is called and epidemiological study. The design of this study uses a group or individual that have been exposed or not been exposed to a certain condition. The parameters will account for similar age, sex working habits etc. This will correctly identify if the contributing factor is the exposure of the agent or otherwise.