by KORIE MARSHALL, EDITOR
With the amount of dust getting blown over and through Valemount the last couple of weeks from the dry lake bed of Kinbasket Reservoir, I’m hearing a lot of people asking – what’s in that dust? And what can we do about it?
The problem is we don’t seem to have those answers.
Should the Ministry of Environment issue air quality warnings on days like Monday, April 18th, when we can barely see Canoe Mountain through the haze, even though the readings at the Fire Hall have been in the green, well under the provincial air quality objective?
Many people are making what I think are some fairly reasonable inferences. There is a lot of sand around and under Valemount, including from the dry lake bed at Kinbasket in the spring. Sand can be made up of a lot of things, including silica. Airborne silica, when inhaled, is dangerous enough to our health that WorkSafe BC requires employers to develop and implement silica exposure control plans.
“We know that silica is a carcinogen,” one resident said to me on Monday. So maybe the sand blowing up Kinbasket by the prevailing wind is dangerous to residents’ health?
First, we don’t really know how much is dangerous. Silica is a natural material, present in lots of things in our environment, and generally, it’s not harmful. We know the problem with silica is that it’s really fine particles are sharp and can embed themselves in the inner lining of our lungs if we breathe them, which is what causes diseases like silicosis.
If the fine particles are the problem, are they more likely blown around, and a long distance away, than the larger particles? That would be another reasonable inference. But I’m not sure what the science says, because it hasn’t been studied much outside of occupational exposure.
One review of studies on exposure, published in the Indian Journal of Occupational and Environmental Medicine, says the relationship between occupational exposure and prevalence of silicosis and silico-tuberculosis has been established beyond doubt in many occupations. It says workers who are exposed to dust containing crystalline silica for about 8 hours per day are at risk of developing silicosis and silico-tuberculosis. To me, that suggests long term, constant exposure – the cumulative effect – is the risk. But the study says silicosis has been underestimated as an environmental disease, and there have been few studies on non-occupational exposure. There are some studies though, and issues like the increase of mining for fracking sand, especially in the US, has meant more people are looking for information on the risks of non-occupational exposure.
One source I read talks about the difference between naturally found silica, like what would be blowing around fields and sand dunes (presumably more rounded and worn particles) vs. those found in industrial applications. If you are cutting concrete, maybe the particles are more rough and sharp. But I haven’t found any science on that either. A volunteer organization that wants to clean off the boat ramp on Kinbasket is required to have a silica exposure plan. They are not cutting anything, just washing the sediment off the ramp, the same sediment that sits all along the dry lake bed. If they need a silica exposure control plan, then someone else has also made the inference that the sand on the lake bed is dangerous.
And if the particles are so small, are they recorded in the local air quality monitors? The Ministry of Environment recently confirmed to me that the PM2.5 monitor on the Valemount Fire Hall would count silica in the particles it measures. But any reading from that monitor doesn’t tell you how much of the dust particles are silica. There is another monitor that actually collects the particulates and they get weighed at some point, but it’s very expensive to do testing on what materials make up the sample, so it’s not usually done.
So we don’t know how much silica we have in the air on days like Monday, and we don’t even know how much is dangerous. We haven’t even gotten into how the risk compares to other known carcinogens that we are exposed to daily, like alcoholic beverages, engine exhaust, and radiation. So I’m not jumping to the conclusion that we need a weir, which would only address part of the problem, while potentially creating many more.
But I want to know more about the risk of silica, and I want to have an idea of how much silica is around Valemount. So how do we start to find out? Looking at available research will help understand the risk, but at some point, we might also need to actually measure the silica in the air.
