Excerpt. © Reprinted by permission. All rights reserved. Excerpt from Donora Death Fog , Chapter 18 The fog that formed on Tuesday settled into the valley like a lazy cousin on a three-week visit. The mill's many chimneys continued to pour forth toxins in its smoke all night, just as they had been doing every day and night for decades, fog or no. Rather than being caught on the wind and transported throughout the region, smoke from the metal factories-and the toxins contained in it-now were trapped. The valley's walls hemmed in the fog and smoke from either side of the river. The temperature inversion blocked the release of fog and smoke upward, and the horseshoe bend in the Monongahela stymied their release to the north or south.

The valley had become by Thursday a lidded mixing bowl, continually blending discharge from cars, trucks, trains, and mill chimneys into what was rapidly becoming a sickening brew of dark gray muck. Even the dark gray color of the air was different. Normally the color of the smoke varied throughout town. Near the blast furnaces at the south end, smoke tended to look black, largely due to coal being used as fuel. In the middle of town, where the open hearth furnaces were, smoke tended to be reddish in color, from the iron ore being broken down. Finally, at the north end of town near the Zinc Works, smoke tended to have a yellowish tinge, the result of sulfur-containing fumes being given off during smelting. With a lid now over the valley the smoke began to blend into a deep, gray mélange of poisonous smoke. Had factory smokestacks been taller than 250 feet, the approximate height of the lowest level of the inversion layer, the effluents coming from them might have spewed into the atmosphere, where they would have become diluted and dissipated over the region.

The tallest smokestacks in Donora, though, were just 150 feet high. Without wind, even a slight breeze, there could be no upward movement of smoke from the plants. So smoke, soot, dust, and toxic gases from the plants, trains, and vehicular traffic in the valley continued to mix into the fog. It seems utterly unlikely that mill owners didn't know how important stack height was to the surrounding communities and, more important, their bottom line. A smelter operator in Montana, the Anaconda Company, constructed a three-hundred-foot stack at its Washoe copper smelter in 1902. Farmers and ranchers near the smelter found that they were losing crops and livestock due, they claimed, to "smelter fumes and poisonous ingredients" contained therein. Fred J. Bliss, on behalf of area residents, sued Anaconda for damages.

Although Bliss, not surprisingly, lost his claim, Anaconda leaders took the lesson to heart, and in 1917 the company removed the smaller stack and built in its place a stack that reached 585 feet into the air, a chimney famously known as the Anaconda Stack. Numerous other smelters at the time also constructed smokestacks more than three hundred feet high, but owners of the zinc smelter in Donora chose otherwise. Andrew Mellon's key lieutenants must have known about the trend toward higher stacks; almost certainly Donora's mill officials did. Why they chose to ignore that trend is unknown, but the decision cost Donora dearly.