Tobacco may benefit ozone, study says

Prevailing winds blow pollutants from large population centers to the area around South Deerfield, Massachusetts, where research was conducted into the effects of ozone on plants

By Environmental News Network staff

May 8, 2000
Web posted at: 2:08 p.m. EDT (1808 GMT)

A University of Massachusetts research team is looking to an unlikely source — tobacco plants — to understand and explain how ozone, the main component in smog, affects plants and humans.

"All around us, we see plants that have endured chronic ozone exposure with no apparent adverse symptoms except premature aging and reduced reproduction," cautions William Manning, a plant pathologist at the university. "Could this relate to the human experience? That's what we need to find out. But, in the meantime, it's important for us to determine how ozone exposure affects our forests, our wetlands, our crops, and even our backyards."

Manning and doctoral student Christopher Bergweiler are studying how tobacco and other plants grown under controlled conditions in glass greenhouses react to different levels of ozone. They're also monitoring ambient, or naturally occurring, ozone and how air temperature, relative humidity, wind speed, wind direction, light, and rainfall affect a plant's reaction to ozone exposure.

Tobacco plants were observed as highly sensitive ozone bioindicators

"The ultimate goal is to use plants to detect periods of ozone exposure that may also affect human health," said Manning.

Manning has spent much of the past 25 years trying to answer one question: Can a tobacco plant in the field serve the same purpose as a canary in a coal mine? The answer, he says, lies in the way a tobacco plant suffers when it is exposed to pollutants, especially ozone.

Manning maintains that most people don't worry much about the health of plants. He views their fragile condition as a symptom of a much larger problem.

"Most people think our breathable air is getting cleaner, and it is in some areas," said Manning. "We have fewer days of extremely bad air, thanks to clean air acts. But steady, day-to-day exposure to pollutants, especially ozone, is becoming more prevalent. On bad days, some plants are getting ozone at concentrations of 60 to 80 parts per billion."

The normal level of ozone in the troposphere — the part of the atmosphere that we breathe — is 25 to 35 parts per billion, said Manning. At higher levels, plants and animals suffer.

As the main component of smog, ozone is blamed for a multitude of human health problems. According to Manning, children, asthma sufferers and elderly persons are especially sensitive to high ozone levels in the air.

Indoor and outdoor labs were used during the ozone research.

"We asked ourselves, 'If we have a lot of ozone in the air on a beautiful summer afternoon, what does that do biologically to humans and plants?' " explained Manning. "One approach is to study the effects of ozone on a cultivar of tobacco that is extremely ozone-sensitive. We grow non-sensitive varieties of tobacco side-by-side with a sensitive one to get a good idea of immediate effects. We can learn about long-term effects by growing varieties of clover, tomato, and selections of milkweed, which respond more slowly.

"The hardest part (of the research) is that it's done outside under natural conditions that are changing all the time," he added. "But those are the conditions that plants are normally exposed to." Normal conditions produce the most reliable results. But even then, it will be 10 years before any clear findings are generated from the experiments, Manning said.

Funding is also a problem. "People don't think ozone needs to be studied anymore," he said.

Copyright 1999, Environmental News Network, All Rights Reserved

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Effects of Ozone on Plants

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