Thick fog and ash covered Bulusan Volcano after it erupted in the Philippines. Video shows the ominous blanket of churning ash and steam obscuring the volcano in Sorsogon, early morning on April 28.

Scientists have long struggled to define brain fog—let alone pinpoint a cause for it. But research is starting to reveal multiple potential causes from inflammation to a leaky blood-brain barrier.

The city government, through the Smoke-Free Baguio Task Force, has deputized more community volunteers as well as security and traffic personnel to enforce Ordinance 34, series of 2017 or the ...