After a carcinogen was found to be seeping up from contaminated soil into buildings, Google is working to protect employees from a mess left behind by the Valley's earliest tech companies.

Over 1,000 Googlers moved into "the Quad" near Whisman Road and Middlefield Road in June of 2012, an area once home to Fairchild and Intel, among others. Those companies used TCE (trichloroethylene) as a solvent in the manufacturing of the first silicon computer chips, leaving behind a massive plume of contaminated groundwater discovered in 1981 -- one that may take many more decades to clean up.

Though regularly tested since 2003, in December Google's new buildings at 369 and 379 Whisman Road were found for the first time to have TCE vapors above the Environmental Protection Agency's indoor screening level, said Alana Lee, project manager for the EPA. The results were blamed on building modifications made for Google that created a pathways through the floor for the vapors to seep into parts of the buildings.

In a recent round of indoor air tests of office buildings above the MEW plume (so named because it is roughly bordered by Middlefield, Ellis and Whisman roads), two office buildings were found to have TCE vapor levels over the limit despite ventilation systems operating: a vacant building at 630 National Drive and 480 Ellis Street -- occupied by surgical equipment maker Aesculap and consultant firm Bristlecone. The latter is undergoing changes to its ventilation system to address the problem.

A Google spokesperson called the levels "anomalous" in its buildings and the causes were "promptly identified and fixed. The health of our Googlers was not put at risk in any way at any time."

TCE's health risks

In 2011 the EPA issued its Final Health Assessment for TCE, calling it "carcinogenic to humans by all routes of exposure" and reporting that inhalation can cause "hepatic, renal, neurological, immunological, reproductive, and developmental effects."

"The potential health concern is long-term exposure to TCE," said the EPA's Lee. "Any exposure would have been for a limited time, a short term. There hasn't been any exposure for a long period of time."

The polluters are financially responsible for indoor air testing and any mitigation measures that are needed, but Google is known for its obsession with reducing common toxic chemicals in its buildings from furniture, paint and building materials, going above and beyond industry standards.

"Google continues to monitor the air quality at the Quad and make the information readily available to Googlers," the spokesperson said.

The buildings now have ventilation systems that run all hours of the day and "activated carbon filters" are used to remove volatile organic compounds like TCE from the air, the spokesperson said.

In the long term, the EPA reports that efforts are underway to install "subslab depressurization systems" under the buildings at 480 Ellis and 369-379 Whisman to draw the vapors away before they can rise into the buildings.

When asked if Google was pushing to have the groundwater cleaned up, the Google spokesperson said, "We'd welcome and expect all the original parties involved to continue to innovate in finding new and improved science for removing this and all chemicals from our groundwater throughout the country."