Several infants and toddlers were rushed to a nearby hospital, where their mothers told doctors the children had difficulty breathing, while some were vomiting.
Another 3,000 people fled their homes in Mary Grace Subdivision in Barangay Sta. Rosa I in Marilao after the toxic chemicals flowed to the Marilao River and affected their environment.
Other affected barangays were Lambakin, Patubig, Tabing Ilog, Ibayo and Nagbalon, all in Marilao town.
Residents, their noses covered with handkerchiefs and some carrying infants bundled in blankets, left their homes before dawn.
"The smell was so unbearable, we couldn’t sleep," said Benjamin Jacinto, head of a local rescue team. "Our neighbors rushed out and had to flee the area."
Health department officials who are investigating the foul-smelling substance said it appears to be used oil mixed with unknown chemicals.
Residents said a tanker truck was seen dumping its contents in the canal in a rice field before dawn, but no one got the vehicle’s license plate.
The oily substance contaminated a farm and the Marilao River, reports said.
Police later found the truck parked in Barangay San Vicente, Sta. Maria town and arrested three men who confessed to dumping the hazardous substance in the canal.
Their truck was rented to transport the substance from a plastic company in Canumay, Valenzuela City, the men added.
Marilao police chief Superintendent Edwin Quilates said the arrested men were Lope Reyes y Dohinog, driver and resident of Camarin, Caloocan City; and truck helpers Alvin Torres and Jose Arnaldo of San Vicente Sta. Maria, Bulacan.
They will be charged with violation of Republic Act 6969 or the Toxic Substances and Hazardous and Nuclear Wastes Control Act of 1990, he added.
Police investigation showed Reyes drove the 10-wheeler tanker truck with license plates XEE-923 and owned by a certain Evelyn Tomas of Pleasant Hill Subdivision in Barangay Muzon, San Jose del Monte, Bulacan.
The truck was reportedly contracted by the CFS Corporation in Camunay, Valenzuela City to dispose of waste products from a plastic manufacturing firm.
It was gathered that that the CFS Corporation is involved in the treatment of chemical waste from factories.
Environment Secretary Angelo Reyes immediately ordered the monitoring and assessment of the illegally dumped substance yesterday.
Experts from the Department of Environment and Natural Resources are awaiting results of laboratory tests made on water samples gathered from the site.
The DENR will also conduct ambient air sampling to determine the exact composition of the hazardous substance.
Exuperio Lipayon, Environment Management Bureau Region III pollution control division chief, said the toxic substance appeared to be petroleum-based or mixed used oil with solvent.
The substance might have volatile organic compound like benzene, and hydrogen sulfide gases that caused the strong odor, which made residents fall sick, he added.
Initial findings of the DENR showed that the irrigation canal where the toxic substance was dumped is located upstream and merely 100 meters away from the Marilao River.
Reports reaching the DENR central office in Quezon City showed that 29 people, 16 of them children, were brought to the hospital due to vomiting and severe headache after inhaling the pungent aroma of the toxic substance.
One hectare of rice field is likewise reportedly affected by the dumping of the hazardous substance.
"The odor strengthened because of the cool weather early yesterday pero kung mainit na, it dissipates into the air... nawawala yung amoy," Lipayon said.
"It is important to determine the exact composition of the sludge in order to come up with appropriate action."
In a statement, Sen. Pia Cayetano said authorities should immediately file criminal charges against those responsible for the dumping of the chemical wastes.
"These shameless polluters deserve to be jailed and must be held accountable with the full force of the law," she said.
Cayetano, Senate committee on environment and natural resources chairwoman, said police should not be satisfied with the arrest of Reyes and his two helpers.
"The police should also go after Reyes’ companions, if he had any, at the time when the chemicals were discharged, as well as the owners and his superiors at the LPG tank cleaning facility where he worked, for it may have been his bosses who actually gave instructions to illegally get rid of the foul-smelling chemicals," she said.
Cayetano said those responsible could face up to P3 million in penalties and imprisonment of up to 10 years if proven guilty of violating Republic Act 9275, the Philippine Clean Water Act of 2004.
The environment secretary may also recommend the closure or suspension of the LPG cleaning facility involved, she added.
Arnold Vytingco, Marilao municipal disaster coordinating office head, said as early as 2 a.m. yesterday, residents of Mary Grace Subdivision at Brgy. Sta Rosa I and nearby barangays like Prenza II, Patubig and Lambakin complained of foul smell emanating from the Marilao River.
Later in the morning, residents of Barangays Tabing-Ilog, Nagablo and Poblacion 2 also complained about the odor from the dumped chemical, he added.
The river flows downstream to Meycauayan and Obando towns, also in Bulacan.
Officials said they cannot assess the damage of the hazardous substance but that aquaculture farms and fisher folk in Meycauayan and the coastal town of Obando would suffer the long term effects.
Environment officials who rushed to the area said they still have to determine the kind of substance dumped in the Marilao River.
Doren Torres, a quick response officer of the Environmental Management Bureau in Central Luzon, said if the substance is used oil, it is hazardous and a regulated substance.
They will check the plate number of the impounded truck if it is one of their accredited transporters of hazardous substances, she added.
Rodolfo Santos, Provincial Disaster Coordinating Office executive officer, said environment officials took water samples for testing to determine what kind of substance was dumped in the river.
Marilao Mayor Epifanio Guillermo said he will ask the police to conduct an immediate investigation. — Wth Katherine Adraneda, Christina Mendez, Cecille Suerte Felipe, Ric Sapnu, AP, AFP