Countries that banned lead in gasoline in the 1970s saw declining violent crime rates approximately 20 years later. Multiple studies across different nations found the same correlation, controlling for economic factors, policing changes, and demographic shifts. Lead exposure in childhood is known to impair impulse control and increase aggression, with effects persisting into adulthood.
The passage suggests that
all violent crime is caused by lead exposure
economic factors have no effect on crime rates
the lead-crime connection has only been observed in one country
environmental policies may have social effects far removed from their original intent
Correct Answer: D
Choice D is the best answer. Banning lead for environmental/health reasons may have reduced crime.
- Context clues: Lead was banned (environmental policy); crime fell 20 years later (unexpected social effect).
- Meaning: The policy had unintended benefits in a different domain.
- Verify: The 20-year lag matches childhood exposure affecting adult behavior.
💡 Strategy: When a policy in one area produces effects in another, infer unexpected cross-domain impacts.
Choice A is incorrect because the correlation doesn't claim lead causes all crime. Choice B is incorrect because studies "controlled for economic factors," meaning they acknowledged their potential influence. Choice C is incorrect because "multiple studies across different nations" found the correlation.