Final answer:
The recent study linking air pollution to reduced brain function was conducted in China, where citizens face severe air quality issues.
Step-by-step explanation:
The recent study that suggested air pollution is linked to reduced brain function was based on tests conducted in China. China is known for its rapid industrialization and economic growth, which has unfortunately led to some of the poorest air quality levels in the world. The smog in China's major cities is so severe that sometimes it even impairs visibility to the point of grounding aircraft. Additionally, the citizens of Beijing have resorted to taking their own pollution measurements due to a lack of trust in the government-issued ratings. These conditions underscore the public's desire for accurate information and effective actions to address the pollution crisis.