Science and Technology for Canadians

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Summary

They used to say that smoking stunted your growth. There's a kernel of truth to that -- smoking cars and factories stunt the growth of food crops. Scientists have suspected as much for years, but no one has ever figured out just how much damage was being done. Not until, Pat Bowen took up the challenge. With colleagues at the University of British Columbia, she's looking to see what impact ground-level pollution, the stuff we call smog, has on crop production in B.C.'s Fraser Valley.

The first step was to flood test crops with ozone, the evil ingredient of smog, to simulate the ebbing and flowing of the urban miasma. The results offered a clear 'before and after' picture of the damage caused by ozone. Next was to determine how much ozone is hanging around the crops in real life. With all this data, Pat is working out the losses to crops caused by smog. The answers can help society decide on emission standards and breeders come up with smog-resistant plants.

Transcript of Video

Jay Ingram
Now, did you drive to the grocery store this weekend to pickup your groceries?

If you DID, it could be damaging the very vegetables you went there to buy.

Your car might be making those vegetables SMALLER.

Some scientists in British Columbia are trying to find the link between the smog your car produces, and the foods you eat.

Jill Deacon
The Fraser Valley in Southwestern British Columbia is a farmer's dream, with soft plots of rich soil and a long growing season. Producers here grow feed grasses and high value crops like vegetables, berries and medicinal plants.

But every year, they're losing money!

Not to competitors, or to natural disasters, but to a new type of thief, smog!

Pat Bowen
We have Vancouver, at the west end, that has a lot of cars, They produce a lot of the primary pollutants that go into making ozone, and we have a climate that... or winds that push this... these primary pollutants up the valley, where we have our farmland, and in sunny warm conditions, that results in the production of ozone.

Jill Deacon
Ground level ozone, or smog, is a pollutant that damages living tissues, like human lungs and plants. It's produced primarily from chemicals in car exhaust. Scientists have known for years that ozone damages crops, but no one has ever measured the amount of damage.

In 1991, Bowen started collaborating with the University of British Columbia, to finally figure out how much agricultural producers are losing, and how much ozone there really is in the valley.

For the first half of the research, they set up test plots at the University, exposed crops to varying levels of ozone, and measured the damage.

Pat Bowen
The zonal air pollution systems, or zaps, consisted of ten very large plots in a field at UBC, where ozone levels are very low, being at the coast. We had eight of the plots that received different levels of ozone exposure, and how we did that is that we had a central trailer in the middle of the field with an ozone generator, and we pumped ozone out to these plots into manifolds that were suspended over top of the whole plot.

Jill Deacon
The whole system was setup to mimic the natural cycles of ground level ozone production, which start off low in the morning, peak around noon, then fade in the afternoon.

Bowen's team still has a lot of data to analyze, but they do have some early results.

Pat Bowen
With broccoli, we found we had ozone damage on the leaves, we found more downy mildew, and we also got smaller heads of broccoli. With strawberry, we found not only did we get less berries, but we got smaller berries, so fewer and smaller. With lettuce, we got smaller heads.

Jill Deacon
The next step was to find out how much ozone is really surrounding crops in the Fraser Valley. Scientists set up 15 monitoring stations in farmers' fields, made up of simple filter papers called "cookies" that were impregnated with indigo dye.

Pat Bowen
Ozone is a very powerful oxydizing agent and indigo dye, which is the dye that we use to dye our blue jeans, will react with ozone to produce a compound called isotyn, and we can detect that with a spectrophotometer.

So what we do is we take our indigo-impregnated cookies, put them out in the field, expose them for a week and bring them back, extract the isotyn with hot ethanol, and then measure how much isotyn was there with the spectrophotometer.

Jill Deacon
Early results show that the levels of ozone vary up and down the valley, depending on the time of year, but it does seem that almost all crops are affected.

Pat Bowen
Remember, most of this injury is invisible, you don't see ozone effects, it's... the plants have the ability to repair some of the damage, but it... it's costly and that takes away from the amount of energy put in to the yield. So, on years that we expect to have really high yields, we find high yields, but maybe they'd perhaps be even higher yet if we didn't have the ozone around.

Jill Deacon
Many plants grow best in lots of sunlight. These periods of active growth are also the times they are most vulnerable to ozone pollution, because lots of sunlight is what triggers the production of ground level ozone.

Pat Bowen
While the estimates for ozone injury to crops range to five to 15 percent reduction in yield, between five and 20-million dollars a year loss, in the Fraser Valley, say... but that's what data we're trying to get, we're trying to be able to quantify the amount of loss... it's important to do that to set policy.

Jill Deacon
The situation in the Fraser Valley isn't likely to improve in the near future. Projects like these generate strategic scientific data for plant breeding programs and for setting emissions standards to reduce smog.

Jay Ingram
Earth Tones is produced with the help of Agriculture and Agri-Food Canada.