Poison Valley, Part 2

What new cocktails of toxic chemicals are brewing in the high-tech industry's "clean rooms" -- and will we ever know what harm they're causing?

By Jim Fisher

Jul 31, 2001 | In the middle of the 19th century, the baleful effects of mercury poisoning were hard to escape for anyone familiar with California's quicksilver mines and refineries. As Gray Brechin writes in "Imperial San Francisco: Urban Power, Earthly Ruin," "a visitor to New Almaden [Mine] in 1857 noted that the smoke from the refinery killed trees and cattle and that, despite short shifts, men exposed to the fumes had 'pale, cadaverous faces,' that 'leaden eyes' are the consequence of even these short spells, and any length of time continued at this labor effectively shortens life."

One of Brechin's recurring themes is that metropolises are sustained by the continuous pursuit of metals, and the energy necessary to produce more of the same. Quicksilver, or mercury, was essential for the reduction of gold ore. For centuries, the chemical phenomenon known as mercury amalgamation was the only financially viable method for extracting gold from stamped quartz or alluvial slurry. The early alchemists, it turns out, were not entirely mistaken in believing mercury a core element in the philosopher's stone, capable of changing waste materials into gold.

A century and a half later, aspiring cities are founded on the reduction of a new precious metal -- the computer chip -- which in the end is just a metalized piece of sand, or silicon.

If there is a philosopher's stone of the computer industry, it is the "photoresist," a mixture of organic solvents and photoactive compounds whose properties are altered upon exposure to light. Essential to the process of optical lithography -- the means by which chip makers "print" ever smaller circuit patterns on silicon wafers -- the photoresist is the chemical underpinning of Moore's Law, which famously predicted that the number of transistors that can be built on a piece of silicon will double every 18 months. It is, in many ways, the representative chemical formulation of the industry.

The photoresist is also, like mercury, potentially quite deadly. In the chip-making process, the photoresist is a solvent typically applied by dropping a small amount in the center of a spinning wafer, spreading a uniform coating across the substrate. According to former IBM physician Dr. Myron Harrison, there is an unusually high potential for worker exposure to photoresists through both inhalation and skin absorption.

As early as 1983, according to Harrison, lab tests had determined that a compound sometimes found in photoresist solvents called trihydroxybenzophenone was genotoxic. Along with the rest of the photoresist ingredients -- xylene and DQ sulfonic acid esters, the former a known neurotoxin, the latter genotoxic and mutagenic; n-butyl acetate, a suspected neurotoxicant and respiratory toxicant; and glycol ethers or EGE, the substances at the center of the industry studies discussed above that are known to cause extensive reproductive and developmental disorders -- the photoresist is one nasty concoction.

But it is only one of many nasty concoctions necessary for keeping the modern-day furnaces of Silicon Valley humming. And it is only through the unflagging efforts of activists, health experts like Joe LaDou and, not least, the pressure brought to bear by lawsuits such as the various complaints levied against IBM that public awareness of the dangers of semiconductor manufacturing -- or the assembly of other high-tech devices, such as the hard drives coated by IBM's Alida Hernandez -- is finally beginning to approach the level of what has long since been known about 19th century industrial processes.

But do we know whether the situation is getting better or worse? The effects of mercury poisoning were fairly easy to spot. The effects of exposure to photoresist ingredients may take many years to manifest. Even more troubling, by the time health experts and corporate executives have caught up to what may have been happening 20 years ago, the pace of technological advancement will no doubt have launched a whole new parade of threats.

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