A persistent haze has hung over Metro Cebu (the densely urbanised metropolitan core of Cebu province in the central Philippines) since April 17, caused by a combination of high temperatures and near-still winds that are preventing air pollutants from dispersing. Philippine environment officials say dry-season heat makes fine particles lighter and more likely to remain suspended, while the absence of wind allows vehicle emissions and construction dust — which together account for an estimated 60–70% of local pollution — to accumulate over the cities of Cebu, Mandaue and Lapu-Lapu. Although the Air Quality Index improved slightly by April 21 to "Unhealthy for Sensitive Groups" from a prior "Very Unhealthy" rating, authorities are advising residents — especially children, the elderly, pregnant women and those with chronic illness — to wear N95 or KN95 masks outdoors and to avoid strenuous activity, particularly during peak traffic hours.