The U.S. Environmental Protection Agency had an emergency-response team at the site of the fire, the Sims Metal Management scrap yard at 699 Seaport Boulevard near the Port of Redwood City.
The air in Menlo Park and Atherton was filled with foul-smelling, acrid smoke for several hours on Sunday. "We're definitely smelling the toxic smoke from this fire, and are hunkered down in the house with the windows closed," a Menlo Park resident posted online Sunday. "Is anyone else getting a headache from it?"
Particulate matter — fine particles of materials including smoke — measured 2.5 micrograms Sunday and was at extremely high levels, said Lisa Fasano, spokesperson for the Bay Area Air Quality Management District.
Such small particles are of concern because they can't be seen and are breathed into the lungs and enter the bloodstream, she said. The actual components of the particulate materials have not been identified, she said.
"Oftentimes — and I don't know if it is the case in this matter — the fires burn so hot that the materials get burned in the combustion of the fire. The bigger issue is that the particulate matter causes an immediate health risk," she said. Symptoms include difficulty breathing and respiratory distress.
She said the smoke was trapped close to the ground because of an inversion layer, a weather occurrence in which temperature increases with elevation rather than the other way around.
Sims Metal, which leases land from the Port of Redwood City, recycles scrap metal, cars, appliances and electronics, and calls itself the largest metals recycling company in the world.
In a statement, Sims Metal officials stated the facility was operational and open for business as of Monday morning.
The cause of the fire is under investigation.
The company stated that it has installed multiple fire hydrants and added and expanded fire lanes and fire access gates to the property in recent years. It also limited the height and quantity of stockpiled material.
Company officials stated that the facility is designed to contain storm water, so none of the water used to fight the fire left the property.
"We always consider adopting additional corrective measures when recommended," company officials said. "We also engage in regular fire prevention training, and inspect our facilities on an ongoing basis, implementing corrective measures resulting from those inspections."
Sims has had several fires at its facilities in recent years. The company has been cited for pollution problems at its Redwood City facility.
In April 2007, a large fire of burning crushed cars at the Sims site sent clouds of smoke over neighborhoods east of U.S. 101. The Bay Area Air Quality Management District cited Sims after residue (including toxic polychlorinated byphenyls, known as PCBs, and heavy metals) from the plant drifted into adjacent wetlands, according to an agency incident report.
In August of this year, Sims had a huge fire at its Jersey City, New Jersey, facility. The same location had a second fire early in October, according to East Coast news reports.
The U.S. Environmental Protection Agency also halted loading of shredded materials onto container ships by the Redwood City facility in 2011, after inspectors found that PCBs, mercury, lead and other pollutants were spilling into San Francisco Bay, according to an EPA findings report and order.
Soils around the facility had high levels of heavy metals and other hazardous substances, EPA officials said at the time.
The "shelter in place" health advisory was lifted around 6:20 a.m. Monday, about 17 hours after the fire was reported burning in an outdoor pile of scrap recylables.
Menlo Park district and Redwood City firefighters responded to the fire, which was deemed under control around 8:30 p.m. Sunday, but firefighters were still working at the site Monday.
No injuries were reported and no evacuations were necessary.
Almanac staff and Bay City News Service contributed to this report.