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Oregon State University Agricultural Research updates

The News About Nitrosamines

There's good news and bad about compounds called nitrosamines that have caused cancer in more than 40 species of laboratory animals and may cause cancer in humans, an Oregon State University scientist says.

"The takeaway messages are that there's been very good attention paid in the United States to nitrosamines in foods such as bacon and beer and there have been reductions, but less attention has been paid to nitrosamines in other sources such as certain industrial settings and cosmetics," says OSU's Richard Scanlan.

Two scientists in a lab.

Food scientist Richard Scanlan, right, and colleague Jim Barbour study nitrosamines, circa 1980. Photo: Dave King

The professor of food science has studied nitrosamines for more than 30 years, including how they form and how to measure and reduce their levels. Last spring he was invited to deliver the opening overview session of a day-long American Chemical Society symposium on the compounds.

Nitrosamines were discovered more than 100 years ago but did not draw heavy scrutiny until 1956 when they were found to cause cancer in laboratory test animals.

Scanlan says Americans are exposed to the compounds via diet, smoking, cosmetics and, with some workers, occupational exposure such as breathing aerosols formed during the manufacture of rubber and during metal cutting.

"It's been known since the 1970s that they were in cured meats such as fried bacon, and they were found in beer in 1979," he says. "There's been a lot of research and a dramatic reduction of their levels in these kind of foods since then. For instance, today there are only 1 to 2 percent of the nitrosamines in beer that there were 20 years ago."

Today in the United States using tobacco and working in certain occupational settings probably present a higher risk of exposure to the cancer-causing forms of nitrosamines than most diets, Scanlan says.

"You could eat a quarter pound of bacon a day and drink a six-pack of beer and the exposure would be less than smoking a couple of packs of even low-tar, filtered cigarettes," he says, though he adds that "these kinds of cross-comparisons are very difficult to make."

The average daily exposure of Americans to carcinogenic types of nitrosamines from foods is thought to have dropped from about 1 microgram a day to perhaps a tenth of that, says Scanlan.

"Most people who work in the field of nitrosamine research seem to feel that this (the current estimated average daily exposure from foods) is not a hazardous level for humans," he says. "But no one can say for sure. No threshold level for nitrosamines has been established for human cancer. No one knows at what dose they pose a problem.

"What researchers do know is that about 90 percent of all nitrosamine compounds tested in experimental animals have been shown to cause cancer," he adds. "That includes research with more than 40 species from mice and rats to hamsters, monkeys and even snakes. That's about the strongest indirect evidence one could amass that they cause cancer in humans if the dose is high enough."

The Oregon State scientist has urged researchers to pay less attention to average exposure rates and more attention to maximum daily exposure rates for carcinogenic nitrosamines. "If anybody is affected," he argues, "it is probably people getting the high daily exposure, such as people who smoke a couple of packs of cigarettes per day."

Scientists making another product from a new oil crop

Oregon State University researchers are developing an additional product from a plant called meadowfoam, grown increasingly by Oregon farmers as an oil seed crop.

Meadowfoam field.

A field of meadowfoam near Silverton, east of Salem. Researchers used genetic material from wildflowers to develop the oil-seed crop. Photo: Bob Rost

Meadowfoam's flowers resemble foam-colored buttercups, so it is sometimes sold as an ornamental. However, the plant's chief commercial asset is the high-grade oil yielded from crushing its seeds. Meadowfoam oil can substitute for whale oil or jojoba oil in making lubricants, cosmetics and plastics.

Researchers Wes Deuel and Sven Svenson of OSU's North Willamette Research and Extension Center at Aurora, just south of Portland, are developing a product called Limnax©, made of crushed meadowfoam seeds, also known as seedmeal. Limnax will be marketed as a high-grade mulch and amendment for both farm and nursery soils.

Limnax may have another commercial use as well, said Deuel, a graduate research assistant. He and Svenson, a horticulture professor, are testing Limnax as a biological, environmentally friendly control of some weeds and pests.

Deuel said Limnax appears to be effective in controlling clubroot and weeds in crops such as cabbage, cauliflower, mustard and turnips.

"Limnax may actually enhance the effectiveness of other biological control tools," Deuel said. "The data we obtain from these studies should provide protocol for use of Limnax applications in other crops such as sweet corn, squash, peppers, onions, green beans, cranberry and strawberry, to name just a few."

Svenson said Oregon's nursery industry has contributed greatly to the research into Limnax.

Earlier research showed that some ingredients similar to those in Limnax acted as an effective pesticide against certain harmful larvae, inhibited growth of some weeds and controlled some kinds of plant diseases, he said.

"For nursery crops grown in containers, Limnax has provided good control of a pesky weed called liverwort," Svenson said. "Limnax could reduce a nursery's need to use herbicides."

Deuel said that is of particular interest to the nursery industry now.

"In light of current restrictions imposed by the EPA on a number of synthetic pesticides, we hope to fast-track this product into registration, thereby providing growers with an effective biological alternative to synthetic compounds," Deuel said.

The initial funding for the project came from the Oregon Meadowfoam Growers. Other contributions have come from the U.S. Department of Agriculture, the Oregon Department of Agriculture, the Oregon Association of Nurserymen, the Horticulture Research Institute, the Oregon Processed Vegetable Commission, the Oregon Caneberry Commissions and donations from various Oregon nurseries.

Why is the mountain quail disappearing?

Researchers at Oregon State University are investigating why the largest quail in North America is disappearing from its eastern Oregon habitat.

Mountain quail still are abundant on the west side of Oregon's Cascades Range, but Michael Pope, an OSU doctoral student, and John Crawford, a professor of wildlife ecology, say in eastern Oregon the bird has been in decline for 50 years.

A hand holding a mountain quail.

A mountain quail. Photo: Mike Pope

The population of mountain quail has dipped so low in eastern Oregon that it is listed as a sensitive species and perhaps is in danger of slipping further, said Pope. A lack of information about the mountain quail's life habits complicates recovery efforts to reverse and remedy its decline.

In 1995, Crawford started a 5-year research project involving the Oregon Department of Fish and Wildlife, the Bureau of Land Management and the U.S. Forest Service. Researchers are collecting information about the quail in Wallowa County, where the birds are in decline, and Douglas County, where quail are abundant.

In addition, a small reintroduction program is studying the results of moving birds from Douglas County into Wallowa County. The goal is to develop guidelines for reintroducing other mountain quail to habitat from which they've disappeared.

That habitat once was extensive.

Lewis and Clark noticed the abundance of mountain quail during their first glimpse of Oregon in 1805. They called them partridge. In 1940, ornithologists commented that mountain quail were found in every county in Oregon.

The last 50 years have brought changes to eastern Oregon that have not favored the mountain quail, Pope said.

Among the likely contributors to the decline of the mountain quail in eastern and southern Oregon are conversion of its wildlands habitat to agriculture, and dam construction, according to Pope.

Changes in the way fires occur also is a factor, he speculated.

Historically, small fires in eastern Oregon, often caused by lightning, cleared out underbrush and stimulated the growth of seed-bearing plants that provide the quail's food. But the policy of fire suppression set the stage for huge, hot fires that destroyed habitat and sterilized seed supplies.

Overgrazing by cattle in the first half of the century also contributed to the quail's demise, as their streamside foraging grounds were trampled, Pope said.

Pope and Crawford's research has yielded clues about the life habits, diet requirements, mating behavior and nesting strategies of the mountain quail.

The researchers have observed unusual reproductive strategies used by mountain quail. Breeding pairs create two nests at the same time. The male incubates one while the female incubates the other.

"These birds exhibit an extraordinary ability to produce a tremendous number of young during one time period, with the female laying up to 26 eggs during one nesting period," said Pope.

Known as"rapid, multi-clutch monogamy," this nesting strategy has never been reported in other exclusively monogamous species.

When the covey of quail hatches, the male and female watch over them separately until the young are old enough to flee from predators. Then the two broods and parents combine into one large covey and stay together indefinitely.

Next summer researchers will attempt to determine the survival rate of mountain quail chicks. According to Pope, the program may be expanded in coming years by the Oregon Department of Fish and Wildlife to bolster other low populations on the east side of the Cascades.

"The hope," he said, "is that information from this project will assist in restoring mountain quail in former ranges."