Ken Griswold’s job literally took his breath away last year, leading to two hospital stays and a seven-month recuperation.

Griswold, then a Penn State Extension educator in Lancaster County, was packing small bags of silage into upright silos used as controls in an experiment to estimate dry-matter losses in bunker silos. Although knowledgeable about the dangers of filling a silo, he fell victim to silo filler’s disease within the seven minutes he spent inside one.

“When I go into a silo I’m always in a full body harness and roped up off the outside, so if there is a problem, they can pull me out and no one is coming down to get me,” he explains. The blower and ventilation fans had also been running for some time to disperse silo gas, another safety precaution Griswold takes.

He didn’t see any tell-tale silo-gas signs – a yellow to grey or black haze – as he hauled three silage bags into the silo, buried them, took measurements and climbed out.

“When I got to the bottom of the silo, I realized that something was wrong, because I couldn’t catch my breath; it took me five minutes or more. So I called my local GP and went to see him.”

The Extension worker mentioned that he’d been exposed to nitrogen dioxide ( NO2 ) gas, which forms from nitrates in corn as a part of silage’s fermentation process. Yet the doctor’s diagnosis was asthma, something Griswold has had all his life.

Griswold went home and uneasily fell asleep in a chair downstairs. Near midnight, he started coughing up pink phlegm.

“When you start coughing that up, it means the insides of the lungs are starting to break down and they can’t exchange oxygen.

“I wasn’t thinking clearly, because the phone was not more than 5’ or 10’ away from me. My thought was to go wake my wife so she could call 911. It took me an hour and a half to get out of the chair and upstairs to wake her.”

Griswold told emergency room doctors that he’d been exposed to silo gas, but they’d never heard of it. A pulmonologist was called in and ordered steroids, antibiotics, anti-inflammatories and pure oxygen.

The NO2, heavier than carbon dioxide, accumulates in the lungs, converts to nitric acid and begins breaking down lung tissue. Fortunately, Griswold lost only 2% of lung function.

He spent five days at the hospital and, two weeks later, suffered a relapse.

“I started coughing up blood. So I went back into the hospital, my lungs inflamed, for eight days. The relapse was much more traumatic to my body than the initial exposure.”

Relapses can occur three weeks and two to three months after an acute exposure. Heavy doses of steriods, for four to six months, can prevent them, he says. He finished his last dose in March.

“I’m extremely lucky to be here and share my experience,” he says.

Griswold believes he took the correct safety precautions. Yet droughty conditions in last year’s corn crop probably increased the level of nitrate in the corn and the level of NO2 produced during the fermentation.

“The highest level of NO2 production occurs three to five days after the filling of the silo. I was in it on the fifth day.”

More farms now have equipment that can fill an upright silo within a day, says Griswold. “That may reduce some of the risk of exposure to silo gas because the maximum production of NO2 isn’t going to happen for another two days. But you still have to take precautions to make sure that you’ve got the space well-ventilated if you’re going to go into that silo.”

Now a technical services manager at Kemin Industries, Griswold remains concerned for the many farmers he’s talked with since the accident. “I can’t count the number of farmers who’ve said, ‘Oh, yeah, I got hit with silo gas and felt bad for a couple of days. Then I got better.’

“They probably got hit with a very small amount of silo gas. It’s chronic exposure – much more detrimental because it causes long-term damage to your lungs. If you are chronically exposed to this over a number of times, you can develop severe lung limitations.”

This may be a year to watch nitrate levels in corn silage, he warns, for many states have been hit with drought.