In a study assessing neurodevelopment in children with parental lead exposure, which group would serve as the proper control?

• A. First graders whose parents never worked at the foundry
• B. First graders whose parents worked at the foundry for 5 years or longer
• C. First graders with other exposure
• D. First graders from a different city

Answer: (A)

In studies of how parental lead exposure might affect neurodevelopment, the comparison group should be as similar as possible to the exposed group except for the exposure itself. Therefore, the proper control is first graders whose parents never worked at the foundry, so they don’t have parental lead exposure but share similar socioeconomic and environmental backgrounds. This setup helps ensure that any observed differences in neurodevelopment are due to the parental exposure rather than other factors. The other groups either involve exposure (parents who worked at the foundry) or introduce different exposures or environments (other exposures or a different city), which would confound the comparison.