The city of Meycauayan and the town of Marilao in Bulacan province share a slot in the list of the world’s 30 most polluted places dubbed as the “Dirty Thirty” based on a study of the Blacksmith Institute.

The problem according to the report:

Industrial waste is haphazardly dumped into the Marilao, Meycauayan and Obando
River system, a source of drinking and agricultural water supplies for the 250,000
people living in and around this suburb of Manila. The river system is extremely
polluted due to wastes received from tanneries, gold and precious metals refineries,
the largest lead smelter in the Philippines, and numerous municipal dumpsites.
Substantial contamination also results from small-scale lead recycling facilities along
the river and from the many tanneries that dump untreated hexavalent chromium-
laced wastewater into the river.